Chow Line: Vitamin D and COVID-19

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My wife heard that vitamin D can help with symptoms of COVID-19. Is that true?

Your question is on the minds of many consumers, as more people have been reaching for vitamin supplements to boost their immune system amid the coronavirus pandemic.

Vitamin D, which plays a wide variety of roles in boosting the immune system, is one of those supplements that has seen increased sales in recent weeks. 

It helps the body absorb calcium, which builds strong bones and prevents osteoporosis. Vitamin D’s effect is significant: If you don’t get enough, your body absorbs only 10% to 15% of the calcium you consume. With vitamin D, absorption jumps to 30% to 40%.

In addition, muscles, nerves, the immune system, and many other bodily functions all require vitamin D to do their jobs properly. Vitamin D also offers benefits against a whole range of illnesses and chronic diseases including reducing your risk of developing multiple sclerosis and heart disease, reducing blood pressure, and reducing your likelihood of developing the flu. 

Several research studies have been or are currently under way looking at the correlation between vitamin D deficiency and mortality rates from COVID-19. 

For example, one such study by led by Northwestern University analyzed data from medical centers in China, France, Germany, Italy, Iran, South Korea, Spain, Switzerland, the United Kingdom, and the United States. It found that patients from countries with high COVID-19 mortality rates had lower levels of vitamin D compared to patients in countries that were not as severely affected.

Another study done by the University of Chicago Medicine found that people who were vitamin D deficient before the pandemic began were 77% more likely to test positive for COVID-19 compared to people who had normal levels.

However, it’s important to note that many of the studies looking at the relationship between vitamin D levels and COVID-19 are observational studies that do not prove causation, medical experts say. 

With that in mind, if you want to start taking a vitamin D supplement, its best that you consult with your doctor to see if you have a vitamin D deficiency and are in need of vitamin D supplements, said Jenny Lobb, a family and consumer sciences educator for Ohio State University Extension.

OSU Extension is the outreach arm of The Ohio State University College of Food, Agricultural, and Environmental Sciences (CFAES).

She said the recommended amount of vitamin D for most people is 600 IU (international units) per day. Infants up to 12 months need less, 400 IU, and adults 71 or older need more, 800 IU.

So, besides a vitamin supplement, what are other sources of vitamin D? 

Nearly all milk in the United States is fortified with vitamin D, at a rate of 400 IU per quart, but that equals just 100 IU per cup. Other dairy foods, including cheese and ice cream, are usually made with nonfortified milk, so they often don’t provide any vitamin D. Fish that’s high in fat, such as salmon, tuna, and mackerel, is a good source. Beef liver, cheese, and egg yolks have small amounts. Many breakfast cereals and juice are often fortified with vitamin D. 

However, there are factors that can impact your levels of vitamin D, including where you live, your age. your skin color, your weight and the foods you. 

For example, people get vitamin D from the sun. One type of ultraviolet radiation converts a chemical in the skin into vitamin D3, which the liver and kidneys transform into active vitamin D. But people with darker skin and older people have more trouble converting the sun’s rays into vitamin D. And most people don’t soak up the same amount of sun in the wintertime or if they are using sunscreen.

Also, certain health conditions can impact your vitamin D levels. People with conditions such as inflammatory bowel disease, liver disease, or cystic fibrosis, among others, may have trouble absorbing vitamin D, which can lead to deficiencies, according to Harvard Medical School.

The best way to know if your vitamin D level is low is to get a blood test. Your doctor can then tell you whether you should take a vitamin D supplement.

Experts caution, however, about taking too much vitamin D, because excess vitamin D is stored in fat tissue. Over time, medical experts say, too much vitamin D can become toxic and lead to hypercalcemia, a condition in which too much calcium builds up in the blood, potentially forming deposits in the arteries or soft tissues. 

It’s also important to note, in addition to vitamin D, there are many vitamins and minerals found in a nutritious diet that can help boost your immune system, Lobb said.

“The key takeaway would be that eating a balanced diet goes a long way in promoting immune function,” she said. “Supplements are sometimes needed or recommended, but that is not always the case. Everyone can strive to eat a balanced diet; dietary supplements of any sort should only be used if recommended by a health care provider.” 

Chow Line is a service of The Ohio State University College of Food, Agricultural, and Environmental Sciences and its outreach and research arms, Ohio State University Extension and the Ohio Agricultural Research and Development Center. Send questions to Chow Line author Tracy Turner, 364 W. Lane Ave., Suite B120, Columbus, OH 43201, or

Editor: This column was reviewed by Jenny Lobb, educator, family and consumer sciences, OSU Extension.

Tracy Turner
For more information, contact: 

Jenny Lobb
Family and Consumer Sciences 
OSU Extension