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Dear Dietitian – What are the impacts of vitamin D on COVID-19?

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PICT Leanne McCrate Dear Dietitian
Leanne McCrate, RDN, LD, CNSC

Dear Readers: As scientists work tirelessly to find a treatment and a vaccine for the coronavirus, a common supplement has come to light as a possible aid in the COVID-19 pandemic. It may be in your medicine cabinet, and your kitchen almost certainly contains a food that is fortified with it. It’s vitamin D, also known as the “sunshine” vitamin.

Observational studies have discovered that countries with high death rates from COVID also have high rates of vitamin D deficiency. Keep in mind that observational studies do not show cause and effect. The same observation was made with cardiovascular disease (CVD) and vitamin D deficiency. However, supplementation of the vitamin did not significantly reduce the risk of CVD (1).

The primary function of vitamin D is to lay calcium to the bones, thereby strengthening them. It also has a role in the immune system. It monitors the release of inflammatory molecules; thus, it manages the body’s response to an infection. In this manner, vitamin D could lessen the severity of a COVID infection.

Another possible role of vitamin D is in the prevention of respiratory infections. Martineau et al. concluded in a meta-analysis that vitamin D supplementation was safe and effective against respiratory infections. They described that patients who were severely deficient in vitamin D had the most benefit (2).

Our bodies manufacture vitamin D through sunlight exposure, but the amount produced varies. People with dark skin do not absorb as much sunlight as those with light skin; therefore, the production of vitamin D is often insufficient. Furthermore, some areas of the world do not receive enough sunlight to produce adequate amounts of the vitamin in the residents. Consequently, these countries tend to have higher rates of vitamin D deficiency.

It is advisable to obtain all nutrients from your diet, but this isn’t always practical. In the US, milk and dairy products are fortified with vitamin D, and of course, there are natural food sources. Fatty fish, such as salmon and rainbow trout, egg yolks, and cod liver oil are healthy sources of vitamin D.

The Recommended Daily Allowance (RDA) for vitamin D is 600 IU (international units) for people who are seventy years or younger, and 800 IU daily for those over the age of seventy. It’s easy to think if a certain amount is healthy, then more must be better. However, it is possible to get too much vitamin D since it is stored in body fat. The main consequence of overdoing it is the buildup of calcium in the blood, which causes nausea, vomiting, and frequent urination. Vitamin D toxicity may also lead to kidney stones.

Is there a role for vitamin D in the treatment of COVID? Simply put, it is too soon to tell. More studies need to be performed to determine if there is a valid link. If you are concerned about your vitamin D status, talk to your doctor. A simple blood test can determine if you need a supplement.

Until next time, be healthy!

Dear Dietitian


  1. Babikir Kheiri, Ahmed Abdalla, Ghassan Bachuwa, et al. Vitamin D deficiency and risk of cardiovascular diseases: a narrative review. Clin Hypertens. 2018 Dec 24; 24:19.
  2. Martineau Adrian R, Jolliffe David A, Richard HL et al. (2017) Vitamin D supplementation to prevent acute respiratory tract infections: systematic review and meta-analysis of individual participant data. BMJ 356:i6583
Leanne McCrate, RDN, LD, CNSC, aka Dear Dietitian, is based in Missouri. Her mission is to educate consumers on sound, scientifically-based nutrition. Do you have a nutrition question? Email her at Dear Dietitian does not endorse any products, health programs, or diet plans.