As COVID-19, the disease caused by the novel coronavirus, nears half a million infected globally, more and more people are seeking ways to prevent illness, from primary measures like social distancing to staying at home and adhering to shelter-in-place orders. According to one health official, an effective prevention method may be shining down on you from the sky or bottled up in your medicine cabinet.
Vitamin D is a fat-soluble vitamin that is naturally present in very few foods, but can be easily obtained from supplements or by exposing yourself to ultraviolet rays from the sun.  Vitamin D has numerous functions in our bodies, like promoting calcium absorption and modulating cell growth, neuromuscular function, and immune function as well.
According to Dr. Tom Frieden, the former director of the U.S. Centers for Disease Control and Prevention, vitamin D’s role in immune health may be very important in helping prevent coronavirus infection.
"Vitamin D supplementation reduces the risk of respiratory infection, regulates cytokine production and can limit the risk of other viruses such as influenza,” Dr. Frieden wrote in an opinion piece on Foxnews.com.  “"A respiratory infection can result in cytokine storms – a vicious cycle in which our inflammatory cells damage organs throughout the body – which increase mortality for those with COVID-19. Adequate Vitamin D may potentially provide some modest protection for vulnerable populations"
This is especially important for people who are Vitamin D deficient.
Dr. Frieden notes that more than 40 percent of adults in the United States may be deficient in vitamin D, especially people who live in northern parts of the United States, where winter months can bring extended periods of cloudy, overcast weather. 
Science supports vitamin D, but no definitive proof yet
Broadly speaking, science lends its support to the idea that vitamin D may help prevent coronavirus, but there is no concrete proof at this time. Dr. Frieden notes in his piece that “there is evidence of seasonality in some respiratory illnesses, including influenza and tuberculosis.”  
“A leading hypothesis is that seasonality is due to the reduction in Vitamin D because of decreased exposure to sunlight in winter months,” says Frieden. “There is no seasonality of influenza or tuberculosis in some tropical climates (such as south India), where weather – and sunlight exposure – remains more constant throughout the year.” 
Sunlight may be the most effective way to get vitamin D.  When the sun’s ultraviolet rays reach your skin, your body triggers vitamin D synthesis.  Diet can also help supplement vitamin D. Eating a diet that includes oily fish and shellfish and eggs with yolk can help you get enough vitamin D in your diet. Dr. Frieden has a few other suggestions for getting the necessary vitamin D:
“We can do lots of things to improve our resistance to infection. These include getting regular physical activity, getting enough sleep, stopping smoking and other tobacco use, and, for people living with diabetes, getting it under control. Taking a multivitamin that includes Vitamin D, or a Vitamin D supplement, probably can’t hurt, and it might help.”
“As we continue to work to mitigate the impact of COVID-19, anything we can do to strengthen our resistance is a step in the right direction.“
Get outside and Eat Well
Dr. Frieden suggests that for now, it’s best for us to go out and get some sun, but take care to maintain social distancing when doing so, staying at least six feet away from others. The winter months can be hard to get the vitamin D we need, even with regular exposure to the sun, so eating a balanced diet with sources of vitamin Dis important, as well as taking a supplement if need be.
Disclaimer:This information is not intended to be a substitute for professional medical advice, diagnosis or treatment and is for information only. Always seek the advice of your physician or another qualified health provider with any questions about your medical condition and/or current medication. Do not disregard professional medical advice or delay seeking advice or treatment because of something you have read here.