Vitamins and supplements are more popular today than they have ever been. But are they all that they are cracked up to be? In this edition of Medical Myths, we address a crop of supplement superstitions and mineral misunderstandings.

The supplement industry is huge. In 2016, the global nutritional supplement sector turned over an estimated $132.8 billion. By 2022, some experts predict that this figure will exceed $220 billion.

According to the National Health and Nutrition Examination Survey, in 2011–2012, 52% of adults in the United States reported using some kind of supplement. In addition, almost 1 in 3 people (31%) took multivitamins.

People, understandably, want to be healthy and free from disease. If popping a relatively inexpensive pill every day ups their chances of a healthy, long life, it is no surprise that supplements are popular.

When you couple the desire to live well with a bold marketing campaign replete with toned bodies and perfect smiles, supplements fly off the shelves.

Before we go on, it is important to note that supplements are important for some people. For instance, the Centers for Disease Control and Prevention (CDC) advise females of child-bearing age to take folic acid supplements.

Similarly, for people who live in colder climes, vitamin D is an important supplement, particularly during the darker months.

If your doctor has asked you to take a supplement of any type, it is important to use it as they advise.

In general, though, for adults without health conditions who eat a balanced diet, the vast majority of supplements are nonessential. As these products sit at the intersection of science and marketing, it is no surprise that there are some misconceptions about their benefits.

1. More is always better

When it comes to vitamins, more is not always better. In fact, more can sometimes be dangerous. As vitamin and mineral supplements are available without a prescription, people can be forgiven for assuming that they are safe at any dosage.

Large dosages of some vitamins can hamper the body’s finely tuned systems, though. For instance, according to the American Cancer Society:

“[T]oo much vitamin C can interfere with the body’s ability to absorb copper, a metal that’s needed by the body. Too much phosphorous can inhibit the body’s absorption of calcium. The body cannot get rid of large doses of vitamins A, D, and K, and these can reach toxic levels when too much is taken.”

Additionally, too much vitamin C or calcium might cause diarrhea and stomach pain. Taking too much vitamin D over long periods can cause calcium to build up in the body, which is called hypercalcemia. Hypercalcemia can weaken bones and damage the heart and kidneys.

2. If the label says ‘natural,’ it must be safe

Sadly, the term “natural” is fairly meaningless in relation to the safety or effectiveness of a supplement. To provide an extreme example, cyanide is a natural compound that ferns produce. Of course, we are not suggesting that any supplements contain cyanide.

Some natural plant compounds do have medicinal properties, but there is more to it than that. For instance, dandelion roots are a laxative, whereas dandelion leaves are a diuretic.

There is also the question of dilution: How much of the plant compound remains in the final product? It might be a minimal trace, or the extract might be highly concentrated.

3. It is fine to take supplements alongside normal medicines

As mentioned above, because supplements do not need a prescription, and many of them claim to be “natural,” there is a widespread misconception that they cannot interact with prescribed medication.

In reality, many of these products contain active ingredients that might interfere with other drugs. Supplements might, therefore, boost or reduce the effects of pharmaceutical drugs.

In a 2012 review, researchers investigated “drug interactions and contraindications associated with herbs and dietary supplements.” They found no fewer than 1,491 different interactions between herbal and dietary supplements and medicines.

In particular, supplements containing magnesium, St. John’s wort, iron, calcium, and ginkgo had the greatest number of interactions.

The fact that the majority of people who take herbal or dietary supplements do not discuss this use with their doctors compounds the potential issues.powered by Rubicon Project

4. Vitamin and mineral supplements protect heart health 

The idea that taking vitamin and mineral supplements will protect our hearts is reassuring. However, a large review and meta-analysis published in 2018 could find no significant benefit. Overall, the authors conclude:

“In general, the data on the popular supplements (multivitamins, vitamin D, calcium, and vitamin C) show no consistent benefit for the prevention of [cardiovascular disease, myocardial infarction, or stroke], nor was there a benefit for all-cause mortality to support their continued use.”

Although they did find that “folic acid alone and B vitamins with folic acid, B6, and B12 reduced stroke,” overall, these effects were small.

5. Vitamin C prevents a cold

Although there is a grain of truth to this slice of “common knowledge,” the evidence that vitamin C can prevent a cold is weak.

For instance, a 2013 Cochrane review dove into existing evidence. The authors’ objective was to “find out whether vitamin C reduces the incidence, the duration, or severity of the common cold when used either as a continuous regular supplementation every day or as a therapy at the onset of cold symptoms.”

The scientists found that vitamin C supplementation did not prevent the common cold in the general population. However, they did conclude that it reduced the severity of symptoms and the duration of the cold.

They also concluded that it “may be useful for people exposed to brief periods of severe physical exercise,” such as marathon runners.

6. Vitamin D prevents cancer

Scientists have carried out a large number of studies to investigate whether vitamin D might help reduce or treat cancer. Despite a great deal of research, as one paper explains, there is still no “consensus on whether vitamin D has a beneficial anticancer effect.”

In 2018, a randomized, placebo-controlled study that involved 25,871 participants investigated vitamin D supplements and cancer risk. The researchers found that “[s]upplementation with vitamin D did not result in a lower incidence of invasive cancer or cardiovascular events than placebo.”

7. Probiotics and prebiotics cure all

In recent years, a dizzying array of products claiming to improve gut health and a myriad of other woes have appeared. In particular, we have all witnessed the rise of probiotics and prebiotics.

Probiotics are foods or supplements that contain microorganisms, whereas prebiotics are foods or supplements that contain compounds designed to promote gut bacteria.

There is no doubt that gut bacteria are vital for good health. The science of the microbiome is still relatively young, but it is already implicated in conditions as disparate as hypertensiondiabetes, and depression.

Although there are still large chasms in our understanding of the relationship between the microbiome and health, one fact that this young field has proven beyond doubt is that it is incredibly complex.

Scientists have demonstrated that probiotics might help with several health issues, including reducing diarrhea associated with taking some antibiotics and easing certain symptoms of irritable bowel syndrome (IBS). However, outside of a few specific conditions, there is little evidence that probiotics or prebiotics can benefit health.

Of course, this might change as scientists conduct more studies. Currently, though, it is marketing that drives the sale of probiotics and prebiotics, using vague terms such as “gut health” and “digestive health.”

According to the National Center for Complementary and Integrative Health (NCCIH):

“[I]n most instances, we still don’t know which probiotics are helpful and which are not. We also don’t know how much of the probiotic people would have to take or who would be most likely to benefit. Even for the conditions that have been studied the most, researchers are still working toward finding the answers to these questions.”

As the authorities do not consider probiotics to be medications, they regulate them less strongly, which introduces other concerns. As one author explains:

“Current regulation of probiotics is inadequate to protect consumers and doctors, especially when probiotics are aimed at the dietary management of serious conditions.”

8. Antioxidants extend life

Oxidation is a chemical reaction that occurs as part of many processes in the human body. Oxidation produces free radicals, which are highly chemically reactive and can damage cells and their components.

Antioxidants are compounds that prevent oxidation, and they include vitamin C, vitamin E, selenium, and carotenoids, such as beta carotene.

In general, fruits and vegetables are rich in antioxidants. As these foods are important for good health, it seems a safe assumption that antioxidants might be one of the reasons why they are so good for us. However, this is not necessarily the case, as the NCCIH explain:

“Research has shown that people who eat more vegetables and fruits have lower risks of several diseases; however, it is not clear whether these results are related to the amount of antioxidants in vegetables and fruits, to other components of these foods, to other factors in people’s diets, or to other lifestyle choices.”

The NCCIH also note that large studies have looked at whether antioxidant supplements can help prevent chronic diseases, including cancer, cardiovascular diseases, and cataracts, but that “[i]n most instances, antioxidants did not reduce the risks of developing these diseases.”

Above and beyond a healthful diet, it sounds plausible that taking antioxidant supplements might reduce oxidation further and, thereby, reduce the risk of disease and death. As with most things in medical science, though, the truth is a little more complex.

There is some evidence that taking antioxidant supplements might reduce lifespan. To investigate this question, Cochrane conducted a large review. They combined the results of 78 randomized clinical trials, which included a total of 296,707 participants.

When the researchers analyzed only the studies with the lowest risk of bias, participants who took antioxidant supplements were 1.04 times as likely to die as those who were either not taking supplements or taking a placebo.

Overall, the Cochrane team concludes that “[t]he current evidence does not support the use of antioxidant supplements in the general population or in patients with various diseases.”

The take-home

Vitamins, minerals, and antioxidants are vital for good health. In general, though, eating a varied, healthful diet will provide people with adequate levels of these.

Aside from vitamin D and folic acid, as discussed in the introduction, for adults, the benefits of supplements appear to be minimal at best. Although the supplement industry is thriving, casting a skeptical eye over companies’ marketing materials certainly won’t do people any harm.

Anyone who is planning on taking supplements but already has an existing condition should speak with their doctor first.

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Scientists have proposed a new therapy for type 2 diabetes. If proven effective, the therapy could help some people discontinue insulin treatment.

Scientists have proposed a new therapy for the treatment of type 2 diabetes, with a proof-of-concept study showing positive initial results. If effective, the therapy may mean that some people can stop taking insulin treatment.

The authors of the research presented their findings at UEG Week Virtual 2020, a conference organized by United European Gastroenterology, a professional nonprofit organization for specialists in digestive health.

Type 2 diabetes

According to the National Institute of Diabetes and Digestive and Kidney Diseases, a person may have type 2 diabetes when their blood sugar is too high.

People gain blood sugar, or blood glucose, mainly from the food they eat. Insulin helps cells access this glucose to use as energy. However, for a person with type 2 diabetes, either their body does not make enough insulin or their cells do not respond to insulin correctly.

This then means that the glucose in their blood increases, which can lead to complications of diabetes, such as heart and kidney disease, visual impairment, and loss of sensation in the limbs. The higher the blood glucose over time, the higher the risk of these complications.

According to the Centers for Disease Control and Prevention (CDC), about 1 in 10 adults in the United States have diabetes, and 90–95% of these individuals have type 2 diabetes.

Doctors typically recommend lifestyle changes, such as being more physically active and eating a more healthful diet, to treat type 2 diabetes, as well as medications to manage a person’s blood pressure and blood glucose levels.

Insulin treatment may be necessary if a person is unable to maintain their blood sugar at normal levels. This treatment can take the form of injections, pens, pumps, or inhalers. It encourages the cells in a person’s body to absorb more blood sugar.

However, people’s perception of the side effects of insulin treatment can be quite pronounced. As a result, doctors may be less likely to prescribe insulin, and, when they do, people may not take it regularly.

Consequently, therapies that can avoid these perceived side effects may be valuable in ensuring that people keep up with their prescribed treatment and avoid risking serious health issues.

Proof of concept

In this context, the researchers behind the present study used a novel technique that scientists first reported using in humans in 2016. Based on those preliminary results, it seemed promising.

The technique is called duodenal mucosal resurfacing (DMR). The duodenum is the first part of a person’s small intestine. DMR involves lifting the mucosal layer of the duodenal to allow the ablation of the revealed area using heated water — a process that removes the cells in the targeted area.

The researchers who developed the DMR technique were trying to replicate the positive impact that bariatric surgery (gastric bypass) has on blood sugar levels with a less invasive technique.

Studies of how bariatric surgery improves blood sugar control have concluded that there is a direct effect from the duodenum in addition to the weight loss that results from bariatric surgery.

DMR can take place in an outpatient setting and is minimally invasive. It involves an endoscope catheter to gain access to the duodenal.

The direct effect of the small intestine on glucose control appears to come from the presence of intraepithelial lymphocyte T cells. These are nestled between the gut cells involved in the absorption of nutrients from food.

Mice without these cells are protected from obesity and heart disease, even when eating a high fat diet.

These intraepithelial lymphocytes reduce the amount of a gut hormone called GLP-1. Therefore, in the current study, the researchers added regular doses of a GLP-1 agonist called liraglutide on day 14.

They did so to counteract the reduced amount of this essential lean, antidiabetic hormone. The study participants also received lifestyle counseling to help reduce their blood sugar levels.

The study involved 16 participants with type 2 diabetes receiving insulin treatment. Of the participants who received the DMR therapy with liraglutide, 12 (75%) were able to stop using insulin and maintain their blood sugar control after 6 months.

Promising initial results

The study participants also saw a variety of benefits to their metabolism.

The participants’ HbA1c readings, which determine a person’s glucose control, had all reduced to below 7.5%. After 12 months, this fell further to 6.7%.

Those who responded to the treatment saw a reduction in their body mass index from an average of 29.8 kilograms per square meter (kg/m2) before the study started to 25.5 kg/m2 12 months after the study. Fat in the participants’ livers reduced from 8.1% to 4.6% after 6 months.

Even for the participants who still needed insulin, the required amount reduced from an average of 35 units per day to 17 units per day after 12 months.

According to Dr. Suzanne Meiring, a researcher at the Amsterdam University Medical Center, the Netherlands, and co-lead of the study,

“A single endoscopic DMR ablation with GLP-1 drugs and lifestyle counseling can lead to discontinuation of insulin therapy in a subset of patients with type 2 diabetes while improving their blood glucose control and overall metabolic health.”

“Many patients with type 2 diabetes are very happy to be able to discontinue insulin therapy, since insulin therapy comes with weight gain and hypoglycemic events.”

Further research needed

It is important to note that this is a very small proof-of-concept study. The researchers presented it as a conference paper, and, therefore, few details are available in the public domain for scrutiny.

The intervention combined two innovative treatments. No details of any side effects of the two treatments (DMR and GLP-1 agonist) are available. While promising, there is a need for larger trials to confirm the results.

Importantly, precisely how and why the therapy appears to work is not yet clear.

The scientists believe that it may work because the mucosal cells that the DMR therapy affects undergo changes in response to unhealthful diets that can promote insulin resistance.

“Based on the results of this study, a large international randomized controlled trial, called Revita T2Di Pivotal, will soon start to further investigate its effectiveness in greater numbers,” says Dr. Meiring.

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Researchers may now have gained a better understanding of how the brain causes the disorienting, disruptive sensation of being outside of one’s body.

Most of the time, the mind and body operate seamlessly as a single entity. At times, however, a person may experience a disconcerting sense of “disassociation,” during which they feel as if they are somewhere outside of their body looking in.

According to Dr. Karl Deisseroth — who is a professor of bioengineering, psychiatry, and behavioral sciences at Stanford University in California — almost 3 out of 4 people who experience trauma report this phenomenon occurring either during or some time afterward.

Also, around 2–10% of the general population experience it at some point in their lives, he adds.

Recently, Dr. Deisseroth and colleagues conducted a study that allowed them to identify, for the first time, the brain mechanism that initiates disassociation.

They have now reported their findings in the journal Nature.

The feeling of disassociation begins with nerve cells in the brain’s posteromedial cortex firing synchronously at a specific rate.

Disassociation can be both troubling and disruptive, and it may become chronic. “In order to develop treatments, and to understand the biology, we needed to know more,” says Dr. Deisseroth.

Now, he adds, “This study has identified brain circuitry that plays a role in a well-defined subjective experience.”

“Beyond its potential medical implications, it gets at the question, ‘What is the self?’ That’s a big one in law and literature, and important even for our own introspections.”

The study also describes the molecular foundation underlying the mechanism that causes disassociation.

The brain’s role

Dr. Deisseroth describes disassociation metaphorically “as the perception of being on the outside looking in at the cockpit of the plane that’s your body or mind — and what you’re seeing you just don’t consider to be yourself.”

Indeed, the study is, in part, based on observations of a person who described the experience as being “outside the pilot’s chair, looking at, but not controlling, the gauges.”

The study authors were working with this individual as part of the Stanford Comprehensive Epilepsy Program. He experienced disassociation during preseizure “auras,” which refers to the time period directly preceding seizures.

The researchers recorded electrical signals from the individual’s cerebral cortex in an attempt to identify the brain activity causing his seizures. They noticed a particular pattern of electrical activity that coincided with the aura. It was occurring in the posteromedial cortex.

The researchers observed a particular rhythm being generated by nerve signals firing synchronously. The signal pulsed at 3 Hertz (Hz), or three times per second.

They subsequently found that if they deliberately stimulated this area of the brain electrically, the individual experienced a disassociation aura but no subsequent seizure.

Confirmation in mice

Previous research has suggested that mice experience disassociation as indicated by changes in their behavior.

For example, if a mouse located on an uncomfortably warm surface simply lifts its foot without licking it to soothe it — as would be expected — it is likely experiencing disassociation. Scientists can induce this state using the drug ketamine.

In the recent study, the researchers attempted to cause disassociation in mice by using light to optogenetically stimulate neurons in the rodent equivalent of the human posteromedial cortex.

When they applied stimulation at the same 3-Hz rate they saw in the human brain, they saw disassociative behavior without the presence of ketamine.

Additional research led to the discovery that a specific protein type called an ion channel is necessary for the generation of the 3-Hz pulse.

Recognizing the role of these proteins could lead to the development of new therapies that more effectively address disassociation and the conditions with which it is often associated, such as epilepsy, borderline personality disorder, and PTSD.

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Studies investigating the role of vitamin D in preventing or treating COVID-19 have drawn conflicting conclusions. But should a lack of evidence stop us from topping up our vitamin D levels as the Northern Hemisphere heads toward winter?

Most people know vitamin D as an essential vitamin for healthy bones and teeth. But researchers have attributed a host of other functions to the vitamin, and one of these is supporting the immune system.

A systematic review and meta-analysis from 2017 in BMJ drew on data from 25 randomized controlled trials to look at whether taking a vitamin D supplement could prevent acute respiratory tract infections.

The international research consortium, led by Prof. Adrian R. Martineau, from the Centre for Primary Care and Public Health and the Asthma UK Centre for Applied Research, at Queen Mary University of London, in the United Kingdom, looked at data from nearly 11,000 study participants.

Prof. Martineau and colleagues concluded that “Vitamin D supplementation was safe and it protected against acute respiratory tract infection overall.”

But does vitamin D have a part to play in COVID-19? By now, a number of studies have looked for links between the vitamin and the condition, and their findings have conflicted.

In this Special Feature, we investigate why some experts have suggested a link between COVID-19 and vitamin D, and we dig deep to explore how convincing the evidence from the latest studies really is.

We also discuss whether taking a vitamin D supplement can have realistic benefits, particularly for those in communities that have been hit the hardest by COVID-19.

Why vitamin D?

A number of experts have cited the 2017 study as circumstantial evidence that vitamin D may have a protective effect against COVID-19.

Their articles have appeared in journals such as The Lancet Diabetes & EndocrinologyBMJ NutritionPrevention & HealthMetabolism, and Aging Clinical and Experimental Research.

The common thread is that they highlight that adequate vitamin D levels may help our immune systems fight off the SARS-CoV-2 virus, as with other viruses that cause upper respiratory infections. People with vitamin D deficiency may, therefore, not be able to do this as effectively.

One aspect of this is that it provides an elegant excuse about why people from marginalized racial and ethnic groups have been disproportionately affected by COVID-19, as some scientists have suggested.

There is already evidence to suggest that people with darker skin tones who live in Northern latitudes have inadequate vitamin D levels.

To make vitamin D, our bodies convert a metabolite of cholesterol in our skin cells into an inactive form of vitamin D when we are exposed to sunlight, specifically to ultraviolet B (UVB) light. This inactive form then undergoes further chemical modification in the liver and kidneys.

The pigment melanin that gives our skin its color stops UVB light from reaching the cells. Hence, the darker a person’s skin, the more UVB light they need to make adequate levels of vitamin D from sunshine alone.

A study in the American Journal of Clinical Nutrition found that 17.5% of Black study participants in the United States were classed as being at risk of vitamin D deficiency, a figure nearly 8.5 times greater than the percentage of their white counterparts who were at risk of the deficiency.

Data from the past few months have shown that in the U.S. and the U.K., Black people are more likely to die if they have COVID-19 than white people.

Given the relationship between vitamin D and respiratory infections, it is perhaps not unsurprising that many people have suggested a tentative link between the vitamin and the disease.

So, let’s look at the studies that have sought to investigate this link in more detail.

Evidence so far

Back in June, the National Institute for Health and Care Excellence, in the U.K., reported that “There is no evidence to support taking vitamin D supplements to specifically prevent or treat COVID‑19.”

The organization based their statement on data from a number of published studies, all of which they deemed to contain a “very low quality of evidence.”

In August, a research team from the University of Glasgow, in the U.K., looked at the vitamin D levels of 341,484 participants in the U.K. Biobank health data repository. Of these, 656 had been to the hospital with COVID-19, and 203 had died.

Once the authors accounted for confounding factors, they concluded that there was no link between vitamin D levels and the likelihood of needing hospitalization for COVID-19 or dying from the disease.

The main limitation, the team noted, was that the vitamin D measurements had been taken roughly 10 years earlier.

Also in August, researchers in Spain reported the results of a small clinical study looking at intensive care unit (ICU) admissions and vitamin D supplementation.

The team gave one group of patients a supplementary high dose of calcifediol, a precursor molecule to vitamin D, in addition to a range of drugs to treat COVID-19. The other group did not receive calcifediol.

“Of [the] 50 patients treated with calcifediol, one required admission to the ICU (2%), while of [the] 26 untreated patients, 13 required admission (50%),” the researchers reported.

While these numbers seem impressive, the study was small and has several limitations. One is that the vitamin D levels of the participants were not measured before and during the study. There were also differences in confounding factors, such as other health conditions, between the two groups.

In addition, the study was open label, so both the researchers and the participants knew who had received vitamin D, which leaves room for bias.

Who tests positive for COVID-19?

A study published at the start of September in JAMA Network Open looked at the vitamin D levels of people who had received a COVID-19 test.

The research team, from the University of Chicago, in Illinois, used data from 4,314 people who had received a COVID-19 test at the university’s medical center between March 3 and April 10, 2020.

Looking at the medical records, they identified 489 individuals who had their vitamin D levels measured sometime in the year prior to the test, but not in the 14 days before it.

From this group, 71 people had received positive COVID-19 test results. Among them, 32 had vitamin D deficiency when their levels were last tested, and 39 did not have the deficiency.

The difference between these numbers did not reach statistical significance.

The team then used a model to predict how many people likely had vitamin D deficiency at the time of their COVID-19 tests, based on previous vitamin D tests and any information about subsequent vitamin D supplements.

When the researchers looked at positive COVID-19 tests in relation to predicted vitamin D status, their model showed that 21.6% of people who likely had the vitamin deficiency at the time of testing would receive positive COVID-19 test results. This figure was 12.2% among people without the deficiency.

While these data may indicate that vitamin D plays a role in the likelihood of receiving a positive COVID-19 test result, the researchers cautiously described the many limitations of their study.

In the paper, they note that “Randomized clinical trials of interventions to reduce vitamin D deficiency are needed to determine if those interventions could reduce COVID-19 incidence, including both broad population interventions and interventions among groups at increased risk of vitamin D deficiency and/or COVID-19.”

Also in September, the journal PLoS ONE published the findings of a large retrospective study conducted by researchers from Quest Diagnostics, in Secaucus, NJ, and the Boston University School of Medicine, in Massachusetts.

The team looked at data from 191,779 people with recorded COVID-19 test results and information about vitamin D levels from tests conducted in the preceding 12 months.

Their analysis showed that 8.1% of 27,870 people with adequate vitamin D levels had tested positive for a SARS-CoV-2 infection, while 12.5% of the 39,190 individuals with vitamin D deficiency had received positive results.

While the data are once again promising, there are a number of limitations. For example, the researchers used a model that the data did not fit particularly well.

Also, the vitamin D test results may not have accurately reflected each person’s vitamin D status at the time of their COVID-19 test. The team acknowledges that there may be other confounding factors that they did not control for.

In addition, it is worth noting that Quest Diagnostics sells a vitamin D test. And the only author of the study who is not directly affiliated with the company — Dr. Michael F. Holick, from Boston University — receives consulting fees from Quest Diagnostics and has authored a book that advocates vitamin D as a cure for common health problems.

Vitamin D and COVID-19 complications

Medical News Today recently reported on a study that looked at the vitamin D status of a group of patients who required hospital treatment for COVID-19.

The researchers found that only 32.8% of the 235 patients had vitamin D levels of at least 30 nanograms per milliliter, which they classed as sufficient. They also saw an association between sufficient vitamin D levels and having less severe COVID-19.

Although the study adds to the body of evidence that argues for a protective effect of vitamin D against COVID-19, it only included a small number of patients, and the researchers did not account for several potential confounding factors, including socioeconomic status, that could have had an impact on COVID-19 severity.

The authors themselves call for larger studies and randomized clinical trials to gain further insights.

Having a data set that is robust enough to account for a range of confounding factors will make the crucial difference between potential associations or correlations and a link that is underpinned by sound scientific data.

But do the effects really matter, when vitamin D can easily be supplemented?

Vitamin D supplements for all?

Writing in The Lancet Diabetes & Endocrinology, Prof. Martineau and Prof. Nita Gandhi Forouhi, of the University of Cambridge School of Clinical Medicine, in the U.K., recently suggested that it is worth taking a vitamin D supplement to ensure adequate levels while clinical studies into the link between vitamin D and COVID-19 are ongoing.

They explain:

“Pending results of such trials, it would seem uncontroversial to enthusiastically promote efforts to achieve reference nutrient intakes of vitamin D, which range from 400 [international units (IU) per day] in the U.K. to 600–800 IU per day in the U.S.A.”

“These are predicated on benefits of vitamin D for bone and muscle health, but there is a chance that their implementation might also reduce the impact of COVID-19 in populations where vitamin D deficiency is prevalent; there is nothing to lose from their implementation, and potentially much to gain,” the authors continue.

Many governments around the world have set recommended daily levels of the vitamin to ensure that people take in enough. This was true before COVID-19.

In the U.S., the National Institutes of Health (NIH) recommend that children older than 1 year and adults up to the age of 70 obtain 600 IU or 15 micrograms (mcg) of vitamin D each day. They advise people aged 71 or older to aim for 800 IU or 20 mcg.

The NIH recommend reaching these targets through a combination of the diet, sunlight exposure, and supplements.

Natural food sources of vitamin D include oily fish, beef liver, cheese, egg yolks, and mushrooms. Many breakfast cereals and milk and non-dairy alternatives are fortified with vitamin D, as are infant formulas.

In the U.K., Public Health England (PHE) recommend 400 IU or 10 mcg per day for people of all ages. Most people are able to get sufficient vitamin D from their diet and sunlight exposure in the spring and summer. This is not necessarily so during the rest of the year.

“Since it is difficult for people to meet the 10 [mcg] recommendation from consuming foods naturally containing or fortified with vitamin D, people should consider taking a daily supplement containing 10 [mcg] of vitamin D in autumn and winter,” PHE recommend.

They also say that people with little or no sunlight exposure due to work or personal circumstances and “Ethnic minority groups with dark skin from African, Afro-Caribbean, and South Asian backgrounds may not get enough vitamin D from sunlight in the summer and therefore should consider taking a supplement all year round.”

In light of the COVID-19 pandemic, the U.K. government is actively encouraging everyone to take a daily supplement of the vitamin, as many people may be spending more time indoors.

Of course, it makes sense for governments and public health bodies to recommend supplements for those struggling to get enough vitamin D.

But the consumption of dietary supplements is not ubiquitous, and there is variability among different racial and ethnic groups.

A 2016 study in JAMA that looked at trends in multivitamin consumption among U.S. adults found that in 2011–2012, 58% of non-Hispanic white study participants took multivitamins. For non-Hispanic Black participants the figure was 41% and for Mexican American participants it was 29%.

It is worth mentioning that excessive levels of vitamin D are toxic. “Vitamin D toxicity almost always occurs from overuse of supplements,” the NIH warn.

The upper daily limit of vitamin D for children aged 1–8, they report, is 63–75 mcg or 2,500–3,000 IU. For children aged 9 or over, teens, and adults, it is 100 mcg or 4,000 IU.

Vitamin D, COVID-19, and skin color

The risk of dying from COVID-19 is disproportionately high among people from marginalized ethnic and racial backgrounds.

In May, MNT reported on large study from the U.K. that found that preexisting conditions could not explain this increase in risk — but that there was a clear association with being a part of a racial or ethnic minority group or having experienced poverty.

Considering this data about COVID-19 risk and the fact that many people with darker skin in Northern climates do not have adequate vitamin D levels: Is the sunshine vitamin the reason that people from marginalized ethnic and racial groups are experiencing worse COVID-19 outcomes?

So far, the hypothesis remains just that.

Future scientific investigations into the suggested link between vitamin D status, COVID-19 outcomes, and skin color may provide clarity.

“Since African American and Hispanic populations in the U.S. have both high rates of vitamin D deficiency and bear a disproportionate burden of morbidity and mortality from COVID-19, they may be particularly important populations to engage in studies of whether vitamin D can reduce the incidence and burden of COVID-19,” the authors of the JAMA Network Open study discussed above note in their paper.

Yet vitamin D is likely only going to be one part of the complex puzzle that is COVID-19.

In a letter published in the Journal of Human Hypertension, a group from the U.S. and Argentina suggest that genetic susceptibility may be to blame. They point to a range of health conditions that affect African Americans more than white Americans.

“The usual explanation for these differences is the low socioeconomic status and educational levels, the social environment, lifestyle habits, and less access to healthcare services,” they write. “However, there are pieces of evidence that these non-favorable conditions are not enough, and there are other influential factors that may help [lead researchers] to a better approach to the real problem, like some genetic [factors].”

However, Dr. Winston Morgan, from the University of East London, in the U.K., has pointed to the lack of “evidence that the genes used to divide people into races are linked to how our immune system responds to viral infections,” in an opinion piece in The Guardian.

Instead, there is mounting evidence that structural racism is a crucial factor in why marginalized communities are harder hit by COVID-19.

In an exclusive opinion piece for MNT, Dr. Morgan discussed the outcomes of a recent PHE review into why COVID-19 disproportionately affects people from marginalized racial and ethnic groups.

He notes that the review’s recommendations focus on the need to address structural problems in health outcome disparities.

Vitamin D does get a mention. The review’s authors highlight the need for “further evidence as a matter of urgency” in order to deepen our understanding of why people of color are disproportionately experiencing negative outcomes of COVID-19.

In an interview with MNT, Assistant Prof. Tiffany Green, from the University of Wisconsin-Madison School of Medicine and Public Health, explained that “Those of us who work in the health disparities space are saddened but not surprised at the race-based disparities that the COVID-19 crisis has brought to light.”

She pointed to the “racialized class and occupational structures of the U.S.” as a major factor that contributes to who is exposed to the SARS-CoV-2 virus.

To conclude, it makes sense to look after our vitamin D levels as part of our general health, and by extension our ability to fight off infections. But science rarely has easy answers.

In order to navigate our way out of the COVID-19 pandemic, we would be better served if we were able to accept that we are up against a complex interplay of societal and immunological factors.

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A new study confirms that older men may lack the bodily cues that help younger men remain hydrated.

Smart thermostats have nothing on our hypothalamus. This is the gland that helps us maintain a healthy body temperature.

When we get too hot, the hypothalamus causes our skin to produce sweat that cools us down as it evaporates. We then become thirsty, and we should drink to replace the water that we lost through sweating.

However, if we sweat too much or do not drink water to replenish our fluids, we can become dehydrated.

Without enough water in the body, we lose the ability to cool ourselves with sweat, and the body can overheat. This increases our chance of experiencing heatstroke and other heat-related damage to our bodies.

As we age, the efficiency of our temperature regulation system declines. Although most research into the effects of dehydration focuses on young adults, a new study in The Journal of Physiology examines its role in the health of older adults.

Older adults may not feel as thirsty as young people and should take care to hydrate when they work or exercise and when the weather is hot.

Dehydration changes as we age

Researchers from the Human and Environmental Physiology Research Unit at the University of Ottawa in Canada explored the paradoxical risk associated with dehydration later in life.

On the one hand, during exercise, dehydration in older adults does not lead as readily to an increase in body temperature through a reduction in heat loss as it does in younger people.

Although this may seem to be a good thing, the lack of sweat and thirst means that the person loses important cues that suggest that it is time to rehydrate.

Without drinking enough water, dehydration in older adults may persist and quietly increase to dangerous levels.

Blood salinity

Scientists have suggested that the reason that older adults feel less thirsty is due to a reduced ability to detect and respond to the level of salt in their blood.

When the balance between water and salt in the blood tips toward salinity, the body of a younger adult responds with feelings of thirst.

The researchers wondered if the same reduced ability to track blood salinity, or “osmolality,” that reduces sensations of thirst may also be the driver behind the less extreme response to dehydration in older adults.

Ten younger men (18–30 years old) and 10 older men (54–67 years old) participated in exercise heat stress tests. The researchers asked them to abstain from consuming alcohol and engaging in strenuous exercise for 24 hours before each session. They also asked them to drink 500 milliliters of water the night before the experiments.

After screening, the men took part in two exercise sessions placed a week apart. At the start of each exercise session, the participants received an intravenous saline solution to increase blood osmolality before entering a heated, whole-body direct-air calorimeter for 1 hour of stationary cycling.

The calorimeter measured the participants’ whole-body evaporative and dry heat loss, and other measurements tracked a range of body indicators of temperature and rate of heat loss.

Analysis of these data revealed a substantive difference in the regulation of body temperature between the younger and older men.

The researchers found that for older men, an increase in blood salinity did not trigger the body’s responses to dehydration as it did in the younger men.

An incomplete picture

Further research will be necessary to help scientists gain a full understanding of heat regulation in older adults.

As first study author Robert Meade says, “While our research design allowed us to test the independent effect of osmolality on heat loss, the effect of reduced blood volume (termed hypovolemia) on sweating in older adults is currently unknown.”

Because the study explored the effects of blood osmolality in physically active participants without any known chronic conditions, it is unclear whether or not the same finding would apply to older adults with common age-related conditions such as type 2 diabetes.

However, Meade concludes:

“Given that common age-related chronic health conditions such as type 2 diabetes are associated with less efficient regulation of body temperature and hydration status, future research should be conducted to see whether our findings translate to or are exaggerated in those populations.”

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A study finds that 10 minutes of massage or relaxation can activate the body’s system for overcoming stress.

The damaging effects of stress are well-known, but fortunately, our bodies have a built-in system for managing and recovering from it. This system is called the parasympathetic nervous system (PSNS).

While there is plenty of anecdotal evidence that taking time to relax — especially when it involves massage — can activate the PSNS, the new study by psychologists at the University of Konstanz in Germany has scientifically measured and confirmed this effect.

In their paper, the researchers conclude that short periods of relaxation may be psychologically and physiologically regenerative and that the effect is even more pronounced with massage.

The senior author of the study is Prof. Jens Pruessner of the university’s Neuropsychology lab, who is a member of the Cluster of Excellence “Centre for the Advanced Study of Collective Behaviour.” He explains the importance of the new research:

“To get a better handle on the negative effects of stress, we need to understand its opposite — relaxation. Relaxation therapies show great promise as a holistic way to treat stress, but more systematic scientific appraisal of these methods is needed.”

The study appears in the September 2020 issue of Scientific Reports.

The study

For their study, the team divided the participants into three groups.

The first group received 10-minute head-and-neck massages with a moderate pressure intended to stimulate the PSNS’s vagus nerve. This nerve contains some 75% of the PSNS nerve fibers, branching out to the many organs in the body with which the system interacts.

The second group of individuals received much softer 10-minute neck-and-shoulder massages as a means of determining the PSNS-activating effect of simple tactile contact.

A third control group simply sat at a table relaxing for 10 minutes.

The researchers used both physiological and psychological measurements to evaluate the degree to which each intervention, or lack of, had activated the participants’ PSNS.

Neuropsychology doctoral student Maria Meier led the team, who assessed the tests’ physiological effect by measuring the participants’ heart rate, as well as their heart rate variability (HRV). HRV is a measurement of variations in the time intervals between heartbeats.

For example, when the body is in fight-or-flight mode, there is very little variation because the heart beats quickly at a steady rate. This will provide a low HRV value. When the body is relaxed, a greater degree of variation occurs, resulting in a higher HRV.

All of the participants had significantly higher HRV levels afterward. However, the most dramatic increases in HRV belonged to those who had received massages. The type of massage did not matter.

Simple tactile contact proved just as effective for helping an individual relax as a massage designed specifically to activate the PSNS.

Psychologically, all participants reported feeling less stressed and more relaxed after the tests.

Overall, the experiments confirmed that simply taking a few moments to relax can help a person manage stress. Adding a relaxing massage does even more to activate the PSNS and alleviate the physical and mental effects of stress.

Stress management

Meier concludes: “We are very encouraged by the findings that short periods of disengagement are enough to relax not just the mind but also the body. You don’t need a professional treatment in order to relax. Having somebody gently stroke your shoulders, or even just resting your head on the table for 10 minutes, is an effective way to boost your body’s physiological engine of relaxation.”

Equally important as the study’s finding is the development of a system for objectively evaluating relaxation therapies. With experts often citing stress as the driver of diseases such as depression, a reliable means of validating relaxation techniques clearly has value.

Says Meier, “Massage, being such a commonly used relaxation therapy, was our first study. Our next step is to test if other short interventions, like breathing exercises and meditation, show similar psychological and physiological relaxation results.”


Data spanning more than 11 years suggest that testosterone injections could be a novel treatment for obesity in men. The results show that long-term testosterone therapy may be comparable to weight loss surgery, with a lower risk of complications.

Over 42% of adults in the United States have obesity, according to the Centers for Disease Control and Prevention (CDC). Obesity has links to several chronic health conditions, including heart disease and type 2 diabetes.

Recent findings that obesity may also worsen outcomes in COVID-19 have encouraged some governments to create entirely new public health strategies to encourage people to lose weight.

However, obesity is a complex issue with both medical and social causes, and achieving lasting weight loss can be challenging for many people. This means researchers are looking for new strategies to help treat obesity — beyond merely cutting calories.

Data recently presented at the virtual European and International Congress on Obesity support the use of testosterone therapy to treat men with obesity.

Long-term testosterone treatment reduced body weight by 20% on average.

11 years of data

The pharmaceutical company Bayer and Gulf Medical University in the United Arab Emirates led the research, using 11 years’ worth of data.

The researchers collected data since 2004 of 471 men with functional hypogonadism, or low testosterone production, and obesity from a German urological practice.

Around 58% of the men received an injection of testosterone every 3 months for the duration of the study, while the remainder chose not to have the treatment and therefore acted as controls. The average age of the participants was 61.57.

Medical staff administered and documented all injections at a doctor’s office, which assures that all participants received the treatment in a consistent manner. No participants dropped out of the study.

20% bodyweight reduction

The men who received testosterone lost on average 23 kilograms (kg) (equivalent to 20% body weight) during the study period, while those who did not receive treatment gained an average of 6 kg.

Body mass index (BMI) correspondingly decreased by an average of 7.6 points in those who received testosterone therapy, compared with an increase of 2 points in the control group.

Waist circumference, which is a risk factor for cardiometabolic disease, decreased by an average of 13 centimeters (cm) in the treatment group, compared with a 7 cm increase in the control group.

The testosterone-treated men also had less internal (visceral) fat by the end of the study period. They may have had a lower risk of cardiovascular disease than those who did not receive treatment.

Overall, 28% of men in the control group had a heart attack, and 27.2% had a stroke during the study period. There were no major cardiovascular events in the men who received testosterone therapy.

Likewise, while more than 20% of the control group developed type 2 diabetes during the study period, nobody in the treatment group developed the condition.

Commenting on the results, Farid Saad of Bayer said: “Long-term testosterone therapy in hypogonadal men resulted in profound and sustained […] weight loss, which may have contributed to reductions in mortality and cardiovascular events.”

An alternative to surgery?

The researchers also presented data specific to men who were eligible for bariatric surgery. This is a surgical treatment for obesity, which encompasses gastric band, gastric bypass, and gastric sleeve surgery.

Rates of bariatric surgery are on the rise in the U.S., with more than 250,000 people undergoing weight loss surgery in 2018 alone.

Although bariatric surgery is a proven means of achieving weight loss, there are serious risks associated with the surgery, which does not always have positive outcomes.

This part of the study included 76 men with class 3 obesity (a BMI of 40 or above), making them eligible for bariatric surgery. Of these, 59 received testosterone treatment and lost 30 kg on average.

The BMI of the men also reduced by an average of 10 points, which could be enough to take them out of the highest obesity class, provided their BMI was less than 50 to begin with.

According to Saad, these results suggest testosterone therapy could be as effective as surgery for weight loss — but without the risk of serious complications.

“We believe testosterone therapy should be discussed with patients as an alternative to surgery and should be considered for male patients who cannot undergo surgery.” – Farid Saad, Consultant in Medical Affairs Andrology, Bayer AG

This study is based on data exclusively from men, and all participants had clinically low testosterone levels. Scientists need to conduct further studies to validate the use of this approach in other populations.


A study of older adults in the United Kingdom finds that people who are lonely are more likely to develop type 2 diabetes, independent of other risk factors such as smoking, alcohol consumption, and weight.

Loneliness, in which a person’s social needs are not met, may be on the rise. A recent report found that almost half of people in the United States sometimes or always feel alone.

Loneliness is even more common among younger generations, with almost 80% of Gen Z and more than 70% of millennials experiencing this feeling.

Some believe that technology may play a part in feelings of loneliness among younger generations, with social media and other forms of online communication increasingly replacing genuine human connection.

Beyond the negative emotional impact of feeling isolated, loneliness is also a major risk to physical health. Research has associated loneliness with coronary heart disease and found that loneliness may be a greater threat to health than obesity.

One study even suggested that people who are lonely have a higher mortality risk than individuals who do not feel alone.

A new study from Kings College London in the U.K. adds to the list of health concerns associated with loneliness, finding that people who are lonely may be more likely to develop type 2 diabetes.

The researchers found that loneliness was a significant predictor of diabetes. This finding held when they took account of potential confounding factors, such as age, sex, ethnicity, wealth, smoking, physical activity, body weight, alcohol consumption, hypertension, and cardiovascular disease.

The findings appear in the journal Diabetologia.

The cohort

The study, which is the first to find an association between loneliness and type 2 diabetes, is based on data from more than 4,000 people aged 50 years and above, with an average age of 65 years. The collection of the data took place during the English Longitudinal Study of Ageing.

At the start of the current study, none of the participants had diabetes, and they all had blood glucose levels within a healthy range.

During a follow-up period of 12 years, 264 people in the study (roughly 6% of the sample) developed type 2 diabetes.

The researchers found that the level of loneliness that people experienced at the start of the study was a significant predictor of who would go on to develop diabetes.

Loneliness predicts diabetes onset

The assessment of loneliness occurred at the start of the study using a scale that a psychologist at the University of California, Los Angeles, developed. The scale requires people to rate questionnaire items such as “How often do you feel that you lack companionship?” and “How often do you feel part of a group of friends?”

The researchers found a significant association between loneliness and the onset of type 2 diabetes, even when they controlled for confounding factors, including smoking, alcohol consumption, weight, blood pressure, and cardiovascular disease.

The association was also independent of mental health factors, such as depression and whether a person lived alone.

“The study also demonstrates a clear distinction between loneliness and social isolation, in that isolation or living alone does not predict type 2 diabetes, whereas loneliness, which is defined by a person’s quality of relationships, does,” explains lead author Dr. Ruth Hackett.

This finding highlights the importance of the quality of human interactions that a person has, rather than the quantity.

Stress-related mechanism?

Although the reason for this association is not yet clear, the researchers suggest that it could be related to how the body manages stress.

Previous research has shown, for example, that loneliness is associated with changes to levels of the stress hormone cortisol, which plays a role in diabetes.

“If the feeling of loneliness becomes chronic, then every day you’re stimulating the stress system, and over time, that leads to wear and tear on your body, and those negative changes in stress-related biology may be linked to type 2 diabetes development,” explains Dr. Hackett.

However, it is important to note that this is currently only a hypothesis. Although this study provides a correlation between loneliness and type 2 diabetes, it does not show a causative link between the two factors.

Other limitations of the study include the fact that there was only one measurement of loneliness during the study. Also, the data on type 2 diabetes were based on self-reporting, rather than objective medical records.

The authors also note that the overall strength of the association between the two factors was small. Nevertheless, the study highlights loneliness as a potential risk factor for type 2 diabetes and provides a basis for future studies to investigate this connection in more detail.

Scientists have found associations between fungi living in the gut and mild cognitive impairment, which can lead to Alzheimer’s disease. They suggest that a ketogenic diet could help prevent the disease by creating a more healthful balance of microorganisms in the gut.

Alzheimer’s Association report that 15–20% of people over 65 experience mild cognitive impairment (MCI), which involves a decline in memory and the ability to think clearly.

Doctors do not consider MCI to be a form of dementia because people who have it are able to function relatively well and live independently. However, MCI is associated with an increased risk of Alzheimer’s disease or another form of dementia later in life.

Developing preventive strategies that can be initiated early is therefore a priority. But despite decades of research, no therapies have been shown to reverse or prevent the brain changes seen in Alzheimer’s.

One potential strategy that scientists have begun to explore involves modifying the diet to influence the microbial communities in the gut.

There is an intimate relationship between the gut microbiome and the central nervous system, with recent research suggesting associations between particular bacterial communities and neurological disorders, including MCI, dementia, and Alzheimer’s.

In one recent study, scientists at the Wake Forest School of Medicine, in Winston-Salem, NC, found a distinctive gut bacterial “signature” in people with MCI.

They also discovered that a diet called the modified Mediterranean-style ketogenic diet altered bacterial communities in the guts of volunteers and reduced biomarkers of Alzheimer’s disease in the cerebrospinal fluid of those with MCI.

This diet contains a limited number of carbohydrates and increased amounts of fats. These are primarily mono- and polyunsaturated fats that come from olive oil and fish.

ketogenic, or “keto”, diet contains very few carbohydrates, which the body uses as fuel. When short on carbs, the body starts to break down its fat reserves to produce molecules called ketones, as an alternative source of energy.

The same group of researchers now reports similar associations between the communities of fungi in the gut — collectively called the mycobiome — the person’s diet, and their risk of MCI.

They report their findings in the latest issue of the journal EBioMedicine.

Fungi and brain health

“Although we do not fully understand how these fungi contribute to Alzheimer’s disease, this is the first study of its kind to reveal their role in our mental health, which we hope will ignite thinking in the scientific community to develop better understanding of them in relation to Alzheimer’s disease,” says principal investigator Hariom Yadav, Ph.D., an assistant professor of molecular medicine at Wake Forest.

“It also indicates that dietary habits such as eating a ketogenic diet can reduce harmful fungi in the gut, which might help in reducing Alzheimer’s disease processes in the brain,” he explains.

The researchers randomly assigned 17 older adults to eat either a Mediterranean-style ketogenic diet (MMKD) for 6 weeks or the American Heart Association diet, which is relatively low in fat and high in carbohydrates.

Eleven of the participants had MCI and six had no cognitive issues. Their average age was 65 years.

The team provided each participant assigned to the MMKD with 2 liters of extra virgin olive oil and encouraged them to eat fish, lean meats, and nutrient-rich foods.

After a 6-week “washout” period during which the participants maintained their regular diets, they switched to their study-assigned diets for 6 weeks.

The scientists monitored changes in the participants’ mycobiomes by analyzing fecal samples and changes in Alzheimer’s biomarkers by assessing samples of cerebrospinal fluid.

Fungal signature and diet

At the start of the study, the mycobiomes of participants with MCI had a distinctive signature, containing more of certain types of fungi and fewer of others, compared with those of the other participants.

As expected, MCI was associated with a high-risk profile of Alzheimer’s biomarkers in cerebrospinal fluid. In keeping with previous findings, following an MMKD appeared to improve this risk profile.

Interestingly, individuals with MCI initially had less fungal diversity in their guts, compared with the healthy participants, but eating an MMKD seemed to restore the diversity.

The researchers note that changes in the populations of gut bacteria of individuals with MCI who ate an MMKD — which they had reported in their previous study — may have had knock-on effects on the fungi.

Some species of bacteria produce substances known to suppress the growth of certain fungi. The authors report that this may explain why eating an MMKD suppressed a genus of fungi called Candida in the guts of participants with MCI.

Candida has been implicated in a range of inflammatory diseases of the gut, including Crohn’s disease and ulcerative colitis.

Inflammation is now believed to play an important role in Alzheimer’s disease, as well. By suppressing Candida and reducing inflammation, say the researchers, eating an MMKD may help reduce the risk of Alzheimer’s.

Study limitations

The authors acknowledge that their study had some key limitations. First, while the researchers advised people to eat certain diets, they did not monitor the participants for this.

It was also a pilot study with a small sample size, making it impossible to account for other variables that might affect Alzheimer’s risk and the population of the gut’s microorganisms, such as lifestyle, gender, and ethnicity.

Moreover, the unique signature of gut fungi and bacteria found in individuals with MCI may be a result of the health issue, rather than one of its causes.

Finally, the changes in the mycobiome observed in the participants assigned the keto diet may have been transient, resulting from fungi in the food.

Eating in the evening is associated with a higher intake of calories, as well as lower quality food, according to a new study.

Maintaining a healthful diet is associated with how late in the day people consume most of their food, according to research presented at the European and International Conference on Obesity (ECOICO 2020).

The study found that people who consume most of their calories in the evening tend to consume more of them and have a lower quality diet.

The study’s aim was to explore the connection between the evening consumption of calories — the measure of energy intake (EI) — and diet quality. Judith Baird, a researcher from the Nutrition Innovation Centre for Food and Health at Ulster University in Northern Ireland, United Kingdom, led the study.

Hunger rhythms

Previous studies have found that hunger follows a daily rhythm and that this rhythm is, in some ways, not what people might expect. Although people typically cease eating during an extended period of sleep, they break that fast with what is often the smallest meal of the day.

Meanwhile, hunger tends to be strongest late in the day, peaking at about 8:00 p.m., after most people have completed the majority of their daily activities.

EI consumption naturally tends to be a response to hunger, and other research has investigated the effect of meal timing on metabolism and other bodily processes. The new study, however, looks at its implications for the quantity and quality of food that people consume.

Data used in the study

Beginning in 2008, the U.K.’s National Diet and Nutrition Survey (NDNS) captured detailed information regarding food consumption, nutrient intake, and nutritional status for individuals over the age of 18 months. Each year, the survey collected responses from a representative sample of 1,000 people. Baird and her colleagues analyzed data from 1,177 adults who participated in the survey from 2012 through 2017.

Overall, the researchers found that the participants were, on average, consuming nearly 40% (39.8%) of their daily EI after 6:00 p.m.

Looking at the data more closely, the researchers divided people into quartiles according to the proportion of their daily EI that they consumed after 6:00 p.m. The people in the lowest quartile consumed less than 31.4% of their EI in the evening, while those in the highest quartile ate more than 48.6% during evening hours.

What the data say

The researchers detected two significant trends in the data. First, the study found that eating later affected the total EI for the day.

People who consumed most of their daily EI earlier tended to eat fewer calories over the course of a day.

The findings also suggested that meal timing affects the nutritional quality of food. Baird and her colleagues assessed individuals’ diets as they had reported them in the food diaries that they had supplied to the NDNS. To do this, they consulted the rankings listed in the Nutrient-Rich Food Index. The index rates foods according to their ratio of important nutrients to calorie value.

People who consumed more of their calories during the evening tended to have significantly poorer quality diets.

“Our results suggest that consuming a lower proportion of EI in the evening may be associated with a lower daily energy intake, while consuming a greater proportion of energy intake in the evening may be associated with a lower diet quality score. – The study authors

The study authors present their insights as just one facet of a deeper understanding of the effect of a person’s daily food rhythms and the amount and quality of food that they consume. They conclude:

“Timing of energy intake may be an important modifiable behavior to consider in future nutritional interventions. Further analysis is now needed to examine whether the distribution of energy intake and/or the types of food consumed in the evening are associated with measures of body composition and cardiometabolic health.”