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Scientists warn against taking high doses of vitamin D for COVID-19

Vitamin D
Claims of a link between vitamin D supplements and a resistance to COVID-19 — or any acute respiratory tract infection — are not supported by good evidence.
People should not take high doses of vitamin D to prevent or treat COVID-19, warns a team of British, Irish and American scientists.

“There is no strong scientific evidence to show that very high intakes (ie, mega supplements) of vitamin D will be beneficial in preventing or treating COVID-19,” write the 21 scientists in a consensus paper published late last week in the journal BMJ, Nutrition, Prevention and Health.

There is good evidence, however, that the excessive intake of vitamin D can be harmful, especially for people with other health issues, such as kidney problems, they add.

In the United States, the National Academy of Medicine has determined that healthy adults (those without a specific disease related to a vitamin D deficiency) need, on average, 600 international units (IUs) of vitamin D daily — until the age of 71, when they need, on average, 800 IUs.

Vitamin D is unique among micronutrients, as it’s produced in the skin during exposure to sunlight. So although the vitamin can be obtained through food (such as salmon, egg yolks and fortified milk), just five to 30 minutes of sunlight exposure twice a week is usually sufficient to meet most people’s vitamin D needs, including those living in Minnesota and other northern latitudes.

Even before the coronavirus pandemic, millions of Americans were taking vitamin D supplements unnecessarily and, in some cases, dangerously. A 2017 University of Minnesota study found that one in five American were consuming vitamin D supplements even though experts say that only about 6 percent of Americans are actually deficient in the vitamin.

In recent weeks, unsubstantiated reports that high doses of vitamin D (up to 10,000 IUs daily, according to some accounts) may lower the risk of getting COVID-19 and/or reduce its severity have spread widely across the media, particularly social media. Sales of the supplement have soared as a result, rising by 22 percent in one week alone in March.

Yet, as the consensus paper makes clear, claims of a link between vitamin D supplements and a resistance to COVID-19 — or any acute respiratory tract infection — are not supported by good evidence.

“It is absolutely essential that advice given to the public is evidence-based, accurate and timely,” stress the paper’s authors. “[A]nything less would mislead and has the potential to cause harm.”

Lack of evidence

As the scientists point out, good nutrition and a healthy lifestyle have a positive effect on the body’s immune system, thus helping individuals resist infections. Vitamin D is certainly one of the many nutrients the body needs to stay healthy. It, therefore, should receive our attention — but “not as a ‘magic bullet’ to beat COVID-19, as the scientific evidence base is severely lacking at this time,” write the scientists.

Calls for the widespread use of high-dose vitamin D supplements to contain the spread of COVID-19 are “based on speculations about presumed mechanisms,” they stress. Those presumptions are not yet supported by direct evidence involving humans.

Previous research has suggested a link between vitamin D levels and the risk of developing upper respiratory tract infections, such as the common cold, but many of those studies have been observational. They don’t — and can’t — prove that the two are connected.

As scientists are frequently heard to say, correlation does not mean causation.

It’s long been observed, for example, that our vitamin D levels tend to dip in the winter. That is also the season when we’re most likely to come down with the flu. But that doesn’t mean low vitamin D levels have anything to do with susceptibility to the flu. Winter is also when we spend more time indoors, which increases our exposure to the respiratory droplets expelled by a cough or sneeze from someone infected with influenza.

In 2017, a meta-analysis of 25 previous clinical trials concluded vitamin D supplementation reduces the risk of respiratory tract infections, particularly among people with low levels of the nutrient in their bodies. But, as the authors of the current consensus paper point out, that meta-analysis had several important limitations. Most notably, two of its studies involved children from the developing countries of Mongolia and Afghanistan. When those two studies are removed from the analysis, the evidence of a benefit from vitamin D supplementation vanishes.

Other research has shown that any kind of treatment tends to be substantially more effective in less developed countries than in developed ones.

A strong immune system

Randomized controlled trials (considered the gold standard of medical research) are currently under way to evaluate the effects of vitamin D supplementation on COVID-19 infections, report the authors of the consensus paper.

“Until there is more robust scientific evidence for vitamin D, we strongly caution against the use of high vitamin D supplementation,” they stress.

In the meantime, to keep your body — and immune system — healthy, follow this advice from the Harvard Medical School:

  • Don’t smoke.
  • Eat a diet high in fruits and vegetables.
  • Exercise regularly.
  • Maintain a healthy weight.
  • If you drink alcohol, drink only in moderation.
  • Get adequate sleep.
  • Take steps to avoid infection, such as washing your hands frequently and cooking meats thoroughly.
  • Try to minimize stress.

And during the current coronavirus pandemic, practice social distancing, too.

FMI: BMJ, Nutrition, Prevention and Health is an open-access journal, so you can read the consensus paper in full on the publication’s website.

Comments (9)

  1. Submitted by David Markle on 05/26/2020 - 11:11 am.

    High does of any fat soluble vitamin such as D and E can be a problem due to accumulation in the system.

    • Submitted by Robert Brown on 05/29/2020 - 10:09 am.

      7 preprints based on COVID-19 positive patients show correlation between low vitamin D and severity and mortality in COVID – some appeared after this paper was submitted some before – so the evidence is there – but it has not been covered by media who it appears would rather rely on press release from Universities ‘bigging-up’ results, sometimes without adequate justification, to get media coverage, leading to stories that sew-saw, and a public who does not know what to believe. Some links to get you started if you are interested,

      Low vitamin D: high risk COVID-19 mortality? Seven preprints suggest that is case. Does low ‘D’ put BAME and elderly, at particular COVID-19 risk? Testing and Data Required.

      Is ethnicity linked to incidence or outcomes of COVID-19?’: COVID-19 ’ICU’ risk – 20-fold greater in the Vitamin D Deficient. BAME, African Americans, the Older, Institutionalised and Obese, are at greatest risk. Sun and ‘D’-supplementation – Game-changers? Research urgently required.

      Preventing a COVID-19 pandemic – COVID-19: Vitamin D deficiency; and, death rates; are both disproportionately higher in elderly Italians, Spanish, Swedish Somali, and African Americans? A connection? Research urgently required!’

  2. Submitted by John Wilson on 05/26/2020 - 11:41 am.

    Unfortunately, this article assumes that anything unproven is useless: whereas ignorance is not science nor a reason to assume any aid is useless. There is no big pharma money in vitamins, so medical tests are not done. That is medicine for profit, not science. Vitamin d3 may explain the differences in covid susceptibility based on skin melatonin.

    • Submitted by Pat Terry on 05/26/2020 - 04:34 pm.

      Utter nonsense. Of course medical tests are done. That’s how we know there is no evidence these things work. And I’d say taking something for which there is no evidence of efficacy is pretty useless.

      Its fortunate that we have people like Ms. Perry writing pieces like this. In a world where people spend billions on homeopathy, think vaccines cause autism, and are scared about 5G, it is very important to have evidence-based analysis.

      • Submitted by Scott Wood on 05/27/2020 - 12:47 am.

        While there has clearly been some research on the topic, I’m a bit skeptical of assuming that when someone says “no evidence” it necessarily means “despite being thoroughly studied” — especially when it says “severely lacking *at this time*” (emphasis mine) and that “further research is justified”. Elsewhere the paper cited says there’s a lack of evidence in *high dose* supplementation, but the MinnPost article dropped the “high dose” qualifier in a couple places.

        The paper being referenced says that, “Low vitamin D status may be exacerbated during this COVID-19 crisis (eg, due to indoor living and hence reduced sun exposure), and anyone who is self-isolating with limited access to sunlight is advised to take a vitamin D supplement according to their government’s recommendations for the general population (ie, 400 IU/day for the UK7 and 600 IU/day for the USA (800 IU for >70 years))8 and the European Union (EU).9”

        The article never mentions the 4000 IU/day threshold that the paper considers the upper limit in the absence of medical advice to the contrary, and there’s another paper on the same journal (“Avoidance of vitamin D deficiency to slow the COVID-19 pandemic”) that says, “Now in the context of the current COVID-19 pandemic, renewed attention to the very high prevalence of severe vitamin D deficiency there and elsewhere is in order. Advanced age, obesity, dark skin tone and risk-related genotypes, particularly in combination, are alarm signs that should prompt corrective action, typically with a moderate, individually tailored dose of supplemental vitamin D. While the preventive potential of supplemental vitamin D should not be exaggerated and the dose kept within recommended ranges (typically well under 4000 IU per day), preventing vitamin D deficiency should be a widely shared goal.”

  3. Submitted by Richard Owens on 05/26/2020 - 02:29 pm.

    I think I know this from reading:

    D allows the body to absorb calcium. Northern indoor folks could stand a 1000iu a day which is standard for a D deficiency. It’s in milk and other foods so a good diet might make it unnecessary.

    When in doubt about supplements, keep in mind they are irregular in dose/strength, unproven and NOT tested or approved by our health science services.

    They are profitable and proven so. P.T. Barnum explained their popularity.

  4. Submitted by Helga Rhein on 05/29/2020 - 01:37 pm.

    The report from Lanham-New et al which you describe mentions the value of sufficient vitamin D for the immune system. You are missing out, however, that the immune function and regulation of appropriate genes need a higher vitamin D level, higher than 25 nmol/l. (Holick, Vieth, Carlberg, Heaney), advocating blood levels above 75 nmol/l. An extensive evidence collection is maintained on a specified website (VitaminDwiki), and improvements in many conditions could be shown when blood levels were higher (osteomalacia, CVD, URTI, depression, COPD, etc) resulting in the worldwide consensus that levels should be higher than 25 nmol/l. A group of 48 scientists has also published a consensus statement in 2015 that a level of 100 nmol/l should be called sufficient. (Scientists call to action) To reach such a level from an average UK level (approx 40 nmol/l) needs much higher doses of vitamin D than 10 mcg.

    By the way 10 mcg, the UK recommended dose for babies and adults, is correct for babies, but certainly not for an adult, it seems logical.

    The US has higher average blood levels, 52 nmol/l, and advise also higher intake for the over 70’s. In the US milk products and orange juice is D-fortified, not so in the UK. I can therefore not understand how this can be called a ‘consensus’ statement ? Deficiency defined as below 25 in UK, but below 50 in US??

    Back to the ‘mega doses’. In order to reach adequate blood levels which can be effective for a healthy immunity most people in the UK would need doses of 3-5000 IU daily, or 10,000 IU for the first few weeks to increase the level. These doses are perfectly safe (Vieth) I have worked as GP in Scotland until recently and for the past 15 years I have treated many people with vitamin D deficiency with such doses and even higher. I have never seen an overdose of vitamin D and I would like to challenge the authors to give me evidence for their scare mongering. In fact it is quite the opposite, it is dangerous to let people stay ignorant to the point that they are afraid to take more than 10 mcg of vitamin D. It is negligent not to assess all the evidence out there. UK citizen’s immune systems are faulty because we all are deficient to a smaller or larger degree. Please look it up and stop spreading old fashioned dietetic advice. Happy to send you all the evidence, some is also on

  5. Submitted by Jeff Freedman on 06/07/2020 - 09:25 pm.

    Apologies Susan, but this article is irresponsible. It’s incredibly important people are getting enough Vitamin D, especially during Covid times. People are likely dying by the thousands because of lack of Vitamin D. Everyone should be getting outside for 15-30 minutes in direct sunlight as much as feasible and/or taking a Vitamin D supplement (at least 1,000 IU).

    There’s 100s of articles about importance of Vitamin D in scientific literature – get educated. I work in advertising, so if I know how to read something peer reviewed, you should too. I crawl out my window on my fifth floor walk up and sit on my fire escape in Manhattan for 30 minutes any day there is sun. I *pray* I get my Vitamin D levels up high enough to be able to combat Covid. Articles should help prevent death, not passively dismiss it.

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