The Relationship Between Vitamin D and COVID-19

Emerging research shows a relationship between Vitamin D levels and COVID-19. A recent study published in the European Journal of Endocrinology found that women with PCOS had a 28% increased risk of COVID-19.

The World Health Organization declared COVID-19 a global pandemic earlier this year and still little is known about the potential protective factors as the world waits for a cure, treatment, or vaccine. Past observational studies found independent associations between low serum levels of Vitamin D and susceptibility to acute respiratory tract infections and even Influenza. Newer research is now showing an association between low levels of Vitamin D and COVID-19. This is important for people with PCOS as vitamin D levels have been shown to be low.

What is Vitamin D?

Vitamin D is a vitamin, yes, but it is also a hormone with vitamin D receptors identified on all the cells in our bodies. Our immune cells use vitamin D to function normally. Vitamin D is antiviral. Through numerous mechanisms, vitamin D can reduce risk of infections. Vitamin D3 promotes optimal immune cell signaling, especially in patients with insufficient vitamin D status.

Read: 3 Major Roles of Vitamin D for PCOS

A Vitamin D deficiency is a serum 25(OH)D level lower than 30 nmol/L. Most people are deficient in Vitamin D. The most common reasons are:

  • Low intake (most foods except for fatty fish, eggs, and dairy do not have vitamin D)
  • Limited sun exposure (The sun is an excellent source of vitamin D. Northern latitudes like the UK, Ireland, Northern Europe, Canada and the northern parts of the USA, northern India and China don’t get as much sun exposure as well as people who are homebound such as nursing homes or not going outside much)
  • Poor skin absorption (as we age our skin is less likely to convert vitamin D into its active form)
  • Darker skinned people are also less likely to absorb vitamin D

Vitamin D3 is the best form of vitamin D to supplement with. Vitamins K1 and K2 can increase the absorption of vitamin D (the PCOS Nutrition Center Ultra Vitamin D has these added). But it’s important to avoid taking mega-doses of vitamin D.  Taking too much Vitamin D can increase levels of calcium and can cause kidney damage. Vitamin D can also be toxic as it is fat-soluble (which is why it should be taken with a meal containing fat) and can be stored in fat tissue.

The recommended daily amount of vitamin D is 600 IU daily for most people (800 IU for >70 years). People with PCOS tend to be deficient in Vitamin D and may find taking 1,000 IU to 4,000 IU daily to reach or maintain optimal levels. If you are deficient in Vitamin D, you may need higher amounts (usually by prescription) to reach optimal ranges of 40-60 nmol/L.

Read: 5 Best Ways to Avoid Getting Sick

The Associations between Vitamin D and Covid-19

Newer research is now showing an association between low levels of Vitamin D and COVID-19, a severe acute respiratory syndrome.

In his research, Dr. Alipio found an increase in serum levels of vitamin D in the body could either improve clinical outcomes or mitigate worst (severe to critical) outcomes of Covid-19 patients, while a decrease in vitamin D levels in the body could worsen clinical outcomes.

Some specific populations of people have been associated to have higher rates of Covid-19. In Italy for example, a country with one of the highest number of cases of COVID-19, 76% of women over 70 years of age (the age group with the highest rates of being ill and dying from the disease) have been found to have low levels of Vitamin D.

The outbreak of Covid-19 occurred in winter, a time when Vitamin D levels are lowest due to limited sun exposure.

Black and minority ethnic people—who are more likely to have vitamin D deficiency because they have darker skin—seem to be worse affected than white people by COVID-19.

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Bottom Line:

There is a relationship between Vitamin D levels and COVID-19, but not enough evidence exists right now to show that vitamin D can prevent, cure or treat the disease. Having sufficient vitamin D may help to boost your immunity to covid-19 if you aren’t getting enough of it. There’s no proof that mega-doses of vitamin D, however, will be beneficial in preventing or treating COVID-19. Adequate Vitamin D can be hard to get so supplementation may be needed, especially for the elderly population who are at an increased risk for Covid-19.

pcos dietitian angela grassiAngela Grassi, MS, RDN, LDN, is the founder of The PCOS Nutrition Center, for which she has been providing evidence-based nutrition information and coaching to people with PCOS for over 20 years. Angela is the author of several books on PCOS, including PCOS: The Dietitian’s Guide, The PCOS Workbook: Your Guide to Complete Physical and Emotional Health, and The PCOS Nutrition Center Cookbook. Angela is the past recipient of The Outstanding Nutrition Entrepreneur Award, The Award in Excellence in Practice in Women’s Health, and The Award for Excellence in Graduate Research, from the Academy of Nutrition and Dietetics. Having PCOS herself, Angela has been dedicated to advocacy, education, and research of the syndrome. Click here to schedule a session with Angela to learn more about how nutrition coaching for PCOS can help you!


  1. Alipio, Mark, Vitamin D Supplementation Could Possibly Improve Clinical Outcomes of Patients Infected with Coronavirus-2019 (COVID-19) (April 9, 2020). Available at SSRN: or
  2. Grant WB, Lahore H, McDonnell SL, et al. Evidence that Vitamin D Supplementation Could Reduce Risk of Influenza and COVID-19 Infections and Deaths. Nutrients. 2020;12(4):988.
  3. Ilie, P.C., Stefanescu, S. & Smith, L. The role of vitamin D in the prevention of coronavirus disease 2019 infection and mortality. Aging Clin Exp Res (2020).
  4. Jakovac H. COVID-19 and vitamin D-Is there a link and an opportunity for intervention?. Am J Physiol Endocrinol Metab. 2020;318(5):E589.
  5. Martens PJ, et al. Vitamin D’s effect on immune function.  Nutrients 2020:1248
  6. Isaia G, Giorgino R, Rini GB et al (2003) Prevalence of hypovitaminosis D in elderly women in Italy: clinical consequences and risk factors. Osteoporos Int 14:577–582.
  7. Mitchell, F. Vitamin-D and COVID-19: do deficient risk a poorer outcome? The Lancet. May 2020.
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