You know vitamin D can help you fend off osteoporosis and falls. But if recent headlines have you thinking you might want to pop some more of it to avoid a severe case of COVID-19, know that researchers are still sorting out how, exactly, a deficiency in the vitamin may make you more vulnerable to the disease's more serious symptoms.
For now, experts such as those publishing in a recent BMJ Nutrition, Prevention & Health report don't recommend you boost your intake to avoid COVID-19 complications. As they wrote, “There is no strong scientific evidence to show that very high intakes (i.e., mega supplements) of vitamin D will be beneficial in preventing or treating COVID-19.” What's more, there are risks involved with downing excessive doses of the vitamin — particularly for those with health conditions such as kidney disease.
While researchers continue to research a possible link between COVID-19 and vitamin D levels, here's what we do know about this bone-building (and muscle-strengthening!) nutrient — and how to know if you need a supplement to get the recommended daily allowance.
Crucial for your bones, heart and more
Could You Be Deficient?
Consider having your vitamin D levels tested if …
- You don't get a lot of sun. People who live in colder climates are particularly at risk for a dip in D levels during winter months, since shorter days and full-coverage clothing limit exposure to UVB rays.
- You're over 50. As we get older, we lose some of our ability to synthesize vitamin D from sunlight and from the food we eat.
- You're carrying extra pounds. Studies have suggested a link between obesity and excess body fat — particularly around your middle — with low vitamin D levels. According to one study, for every 10 percent increase in body mass index (BMI), a person can expect to have a 4.2 percent drop in blood levels of vitamin D.
- You have dark skin. Excess melanin, the protective pigment that gives skin its color, hinders the skin's ability to make vitamin D from sun exposure.
- You've got gut issues. Conditions that affect our gastrointestinal system, such as Crohn's disease and celiac disease, do not allow the intestines to absorb enough vitamin D. Certain medications — steroids, for one — can also mess with absorption.
By now, most of us know that vitamin D plays an important role in promoting the absorption of bone-fortifying calcium. But in this case, more is not necessarily more: “If your vitamin D level is sufficient, it doesn't seem like you get a lot of benefit from supplementation,” says Karl Nadolsky, , a clinical endocrinologist and clinical assistant professor of medicine at Michigan State University.
Those of us who are deficient in the vitamin — an oft-cited study puts the number at over 40 percent of the U.S. population — may reap benefits from raising their levels. “We know that having very low levels of vitamin D is bad for a lot of things, especially bones,” Nadolsky says. “It's certainly associated with a lot of things, like type 2 diabetes, cardiovascular health, even early death.” Vitamin D deficiencies have also been linked to breast cancer. Problem is, it's hard to tell if a deficiency of this type is a consequence of ill health, or its cause.