While scientists have feverishly investigated the best ways to reduce risk for COVID-19, the public has received scant information about a potentially powerful protector—maintaining healthy vitamin D levels.

Since the pandemic began, studies conducted in various countries have uncovered a strong association: Deficiency of vitamin D—the “sunshine vitamin”—has been linked to a significant increased risk of getting and dying from COVID-19. For example…

When more than 191,000 COVID-19 patients in the US were studied, those with vitamin D deficiency were 54% more likely to contract the illness than those with adequate levels, according to a study published in PLOS One.

Among nearly 200 hospitalized COVID-19 patients in Spain, 82% were found to have vitamin D deficiency, according to research published in The Journal of Clinical Endocrinology & Metabolism.

When researchers tracked 186 patients hospitalized for COVID-19 in Belgium, those who were deficient in vitamin D were nearly four times more likely to die, according to a study published in American Journal of Clinical Pathology.

While these studies are observational and do not prove that vitamin D deficiency causes worse outcomes for COVID-19, the strong association demonstrates a need for more research. Clinical trials are now under way to consider how adequate levels of the vitamin might be recommended to treat and/or prevent the illness.

Earlier research has shown that worldwide approximately 50% of people have low levels or deficiencies of vitamin D, with older adults, individuals who are obese, African-Americans (as well as anyone with dark skin) and nursing home residents having the greatest risk.

What’s the best way to keep your vitamin D levels where they should be?

Sun exposure accounts for 50% to 90% of one’s vitamin D levels. Just about 20 minutes in the sun each day is required, but with modern-day indoor lifestyles, few people get that much sun exposure. Foods, including fatty fish (such as salmon and mackerel), egg yolks and fortified milk and other products, provide some but very little vitamin D.

A safe alternative: Taking 1,000 international units (IU) of vitamin D daily as part of a multivitamin is a convenient and safe approach for most adults. For additional benefits, it is safe and reasonable to get up to 2,000 IU of vitamin D daily. The absorption of vitamin D3 is typically superior to that of other forms of the vitamin.

Before starting any new supplement, it’s always wise to first check with your physician. He/she may recommend a blood test to check your vitamin D levels.