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The #1 Best Supplement to Take For Immunity, Says Science

Give your immune system a serious boost with this nutrient.

These days, we're all interested in how we can boost our immunity, and many of us are looking to supplements for help. Usually, health experts downplay supplements and say getting your nutrients from whole foods is best, but that's not the case here. There is one supplement that has distinct advantages for immunity, and many of us don't (or can't) get enough of the nutrient naturally. Read on to find out what it is—and the health of others, don't miss these Sure Signs You Have "Long" COVID and May Not Even Know It.


What Dr. Fauci Says

Shot of woman nutritionist doctor writes the medical prescription for a correct diet on a desk with fruits, pills and supplements.

Dr. Anthony Fauci, the nation's top infectious disease expert, says he's a fan of two supplements to improve immunity—Vitamin C and Vitamin D—and takes both on a daily basis. "If you're deficient in vitamin D, that does have an impact on your susceptibility to infection," said Fauci in an interview last fall. "I would not mind recommending—and I do it myself—taking vitamin D supplements."

He added: "The other vitamin that people take is vitamin C because it's a good antioxidant, so if people want to take a gram or so of vitamin C, that would be fine."


The Science on D

illness young woman sneezing in a tissue

"There is good evidence that if you have a low vitamin D level, that you have more of a propensity to get infected when there are infections around," said Dr. Fauci. "Those data are pretty good data."

For example: A review of studies involving 11,321 people found that those who took weekly or daily vitamin D supplements were less likely to develop respiratory tract infections than those who didn't. 

Additionally, "Laboratory studies show that vitamin D can reduce cancer cell growth, help control infections and reduce inflammation," notes the Harvard T.H. Chan School of Public Health. Vitamin D also helps the body absorb calcium, which protects bone health. 

"There is clear evidence that vitamin D does help fight off respiratory infections," Amesh A. Adalja, senior scholar at the Johns Hopkins Center for Health Security, told Health magazine. There is less data showing that vitamin C boosts immunity, but "it doesn't hurt" to take it, he said.


What Doesn't Work

vitamins in store

Fauci was also asked if other much-touted supplements and foods—such as elderberry and spinach—can boost your immunity. He said the answer is no. The data just isn't there.


What Is Vitamin D?

Vitamin d

Vitamin D is known as "the sunshine vitamin," because it's produced naturally by our bodies when sunlight hits the skin. It's also present in a few foods like fortified milk, fatty fish and egg yolks. But many Americans have insufficient levels of the vitamin, and a smaller number have vitamin D deficiency. 

"For most people, the best way to get enough vitamin D is taking a supplement because it is hard to eat enough through food," says the Harvard school of public health.


How Much Vitamin D Should You Take?

woman taking vitamin d supplement with water
Shutterstock / TashaSinchuk

You might want to ask your doctor for a blood test to determine your vitamin D level. And it's always a good idea to consult your doctor before adding a new supplement to your routine.

According to the Office of Dietary Supplements at the National Institutes of Health, adults up to age 70 should get 600 IU of vitamin D daily from all sources. Adults 71 and older should get 800 IU. The daily upper limit of the supplement is 4,000 IU.


Other Ways to Boost Your Immunity

flexitarian diet foods

Besides Vitamin D, Dr. Fauci has three other tips on how to boost your immune system:

  • "Get a reasonable amount of sleep." Fauci and other experts recommend seven to nine hours of quality sleep each night.
  • "Get a good diet." Health experts like Fauci sum this up as focusing on whole foods like fruits and vegetables, lean protein, olive oil and nuts, while limiting processed food, fast food, saturated fat and added sugar.
  • "Try to avoid or alleviate severe stress, which we know can sometimes impact the immune system."

And to get through this pandemic at your healthiest, don't miss these 35 Places You're Most Likely to Catch COVID.

Michael Martin
Michael Martin is a New York City-based writer and editor. Read more about Michael