What is the link between vitamin D and COVID-19?
Recent research indicates that healthy vitamin D levels may make infection by the SARS-CoV-2 virus less likely and reduce the body’s inflammatory response to the virus helping to limit severe complications.
And there’s research to suggest that boosting our vitamin D levels may offer greater protection. A study conducted before the COVID-19 pandemic showed vitamin D supplements were safe and protective against respiratory infections. Of the study’s participants, those with the lowest vitamin D levels going into the study experienced the most significant drops in infection rates while on the supplements.
Clinical trials are in place to give us information about the impact of vitamin D supplements on the COVID-19 infection specifically. At this time, we don’t know if taking moderate or high doses of vitamin D will prevent COVID-19 or reduce the rates of severe complications.
Even though there’s still much we don’t know about the SARS-CoV-2 virus, we do have reason to believe that vitamin D will help your body fight it.
How do you get vitamin D?
Our main daily sources for vitamin D are diet and incidental sun exposure.
The foods that naturally have vitamin D are fatty fish like salmon and tuna, eggs, and sun-dried mushrooms. And many staples like dairy milk, plant-based milks like almond milk, orange juice, and breakfast cereals are fortified with vitamin D (check product labels to confirm).
Your body makes vitamin D when your skin is exposed to sunlight. Getting outdoors to exercise is a great way to boost your vitamin D, but you still need to protect yourself from skin cancer. If you’re outside for an extended time you’ll want to put on sunscreen and wear protective clothing. Tanning is not recommended.
Do you get enough vitamin D?
For most adults the recommended daily allowance for vitamin D is 600 IU (for those over 70, the recommendation is 800 IU). Many can meet this requirement with sun exposure and diet, but that’s not the case for everyone. There are variations in how well individuals synthesize vitamin D from the sun, absorb it from their diet, and process it in their bodies—and, of course, there are differences in sun exposure by season, latitude, and other factors.
As you age, your skin’s capacity to produce vitamin D with sun exposure decreases. People with darker skin need more sun exposure to make vitamin D. If you couple that with limited time outdoors (an older African American in a nursing home, for example), the risk of vitamin D deficiency can be high.
Also keep in mind that certain illnesses can put you at risk for deficiency. Vitamin D is a fat-soluble vitamin and people who are obese may have low levels because body fat can trap vitamin D and keep it from reaching the blood stream. Diseases that result in poor fat absorption including celiac disease and Crohn’s disease can lead to poor absorption of vitamin D from the diet. Also, those with chronic kidney disease or liver disease may not be able to process the vitamin D obtained from sun exposure or diet to the active version of vitamin D used by the body.
You can check for vitamin D deficiency with a blood test that looks for 25-hydroxyvitamin D. It may be useful to determine treatment for people who are at high risk because of limited sun exposure, medical conditions, or poor bone health including osteoporosis or a low-trauma fracture. The test is not recommended universally for everyone.
Do you need a vitamin D supplement?
If you’re not sure you’re getting enough vitamin D from sun and food, it’s reasonable to take a supplement. If you already take a multivitamin it probably has vitamin D. Check the supplement facts label, ideally 600 to 800 IU per day is good, but up to 2000 IU is fine. If you have a medical condition that puts you at risk, talk to your doctor.
But supplements aren’t the only option. Dr. JoAnn Manson, professor of medicine at Harvard Medical School and an expert on vitamin D, stresses the importance of avoiding vitamin D deficiency through lifestyle modifications. Go outside and enjoy the sun in moderation as you’re being physically active, while social distancing. Take time to choose vitamin D-fortified foods when you’re at the grocery store, or eat more fish. All these healthy habits will reduce the risk of vitamin D deficiency and help optimize your immune system to fight the COVID-19 virus.
There are reports of people taking mega doses of vitamin D to protect themselves from COVID-19. There is no evidence at this time that high doses of vitamin D will help. We need to wait until more information comes from randomized clinical trials (Dr. Manson is leading one of those trials). Taking mega doses of vitamin D without a doctor’s guidance could be dangerous. For example, cod liver oil might be taken for vitamin D, but it also has vitamin A that, at high doses, can be toxic to the liver and lead to bone fractures.
Regardless of what the research with COVID-19 shows in the future, vitamin D will still be vital for healthy bones, so maintaining normal vitamin D levels and avoiding vitamin D deficiency is important. And we know correcting low vitamin D levels will boost the immune system. So, get outside as much as you can and maintain a healthy diet.