Not too long ago, Vitamin D emerged as the star of the show when it came to proactive and preventive health care. Seen as the vitamin essential for bone health, it also was suggested that low levels of vitamin D could be linked to a number of other health complications.

Now, Vitamin D has once again been thrust into the spotlight — this time because of its link to COVID-19. A recent study showed that out of all its participants, almost 60% of COVID-19 patients were vitamin D deficient when admitted to the hospital. In another study, researchers found there could be a possible link between vitamin D deficiency and COVID-19 severity.

As vitamin D is starting to become a focal point of COVID-19 prevention, more and more people are turning to supplements to protect themselves. So, what exactly does vitamin D do? How do we get vitamin D? And when should you turn to supplements to up your vitamin D intake?

Why is vitamin D important?

Responsible for increasing intestinal absorption of calcium, magnesium and phosphate, Vitamin D plays a vital role in your overall health. It’s essential for bone density, building your immune system and regulating cell growth, among other key biologic functions.

Research has suggested that low levels of this vitamin may be linked to diabetes and heart disease. Studies have shown that people with low levels of vitamin D and high blood pressure had nearly twice the rate of heart attack as those with adequate levels, although the reason was not clear.

Vitamin D may also play a role in a variety of other health problems. For instance, it may help to regulate brain health, including protecting against memory loss and depression. And although more research needs to be done, some studies show that vitamin D may even protect against multiple sclerosis.

How to get your vitamin D

There are multiple ways to get your daily dose of vitamin D. This can be through diet, supplements and even taking in a little bit of sunshine.

While there are multiple ways to obtain vitamin D, it can be hard to maintain the optimal level – especially through diet or if you live in an area where you can only retain vitamin D from the sun for a few months each year.

“Part of the difficulty of maintaining vitamin D levels is because there are not a large variety of foods that contain much Vitamin D,” says Kristin Gustashaw, MS, RD, LDN, CSG, clinical dietitian at Rush University Medical Center. With that said, it is still a good idea to add foods with vitamin D to your diet.

These are some good food sources:

• Egg yolks
• Milk
• Cheese
• Fatty fish, especially wild-caught salmon and mackrel
• Canned tuna in water
• Sardines
• Beef or calf liver
• Vitamin D-fortified products, including certain cereals, bread, orange juice, yogurt and soy milk

Gustashaw also recommends that you should get out in the sun for at least 15-30 minutes a day – when the sun is available.

“Consider the amount you get from the sun as extra protection, says Gustashaw. “Be sure to get a constant source from your diet and supplementation all year round.”

Supplements can also be a great source of vitamin D, especially if you aren’t getting your daily dose through diet or sunlight.

According to Gustashaw, “Adults should get a minimum oft 600 IU of vitamin D each day and 800 IU if over age 70. Children should get 600 IU each day. And infants 0-12 months 400 IU/day.”

You can learn more about the daily allowance for vitamin D on the National Institutes for Health vitamin D fact sheet. 

Vitamin D and COVID-19

As researchers continue to study possible links between vitamin D deficiency and COVID-19, the big question is: “Should I increase my vitamin D intake?”

The answer varies from person to person and depends on your vitamin D levels. If you are already experiencing a vitamin D deficiency, it may be a good idea to increase your intake — not just as a preventive measure for severe COVID symptoms but also for your health overall.

“We know that a large percentage of the population has suboptimal levels of vitamin D. In fact, as many as half of the U.S. population may be deficient in vitamin D,” explains Gustashaw. “This can possibly lead to symptoms including fatigue, tiredness, hair loss, delayed wound healing, decreased immune health, muscle pain and more, with no other known causes.”

Gustashaw says you can determine your vitamin D levels through a blood test. A low level is 25-hydroxyvitamin D less than 30 ng/mL; a severe deficiency is 25-hydroxyvitamin D less than 5 ng/mL.

If you determine that you do have a lower than desired level, it always best to talk to your health care provider or dietitian about the best way to boost your vitamin D intake. And be mindful of any medications you may be taking that may affect vitamin D absorption, including steroids (e.g., prednisone); the cholesterol-lowering drug cholestyramide; and the seizure medications phenobarbital (Luminal) and phenytoin (Dilantin).

While Vitamin D toxicity is rare, and known cases are associated more with manufacturing errors, research has not that proven taking much more than the upper limit of the recommended dosage  is beneficial. Remember, unless you are trying to replete your stores when deficient, consistently taking excess amounts of vitamin D can, in some cases, lead to renal failure, calcification of soft tissues throughout the body (including in coronary vessels and heart valves), cardiac arrhythmias, and even death.