Dr. Fauci Says It's Fine to Take Vitamins C and D to Help Boost Your Immune System—Here's What to Know

But he advised against taking a few other popular supplements.

When Anthony Fauci, MD, says something about health, people listen—and in a new Instagram Live interview with Jennifer Garner, he opened up about how taking certain supplements may help keep your immune system in top working order.

"If you're deficient in vitamin D, that does have an impact on your susceptibility to infection,” said Dr. Fauci, director of the National Institute of Allergy and Infectious Diseases. “I would not mind recommending, and I do it myself, taking vitamin D supplements.” But that's not all: Dr. Fauci also recommended another vitamin. “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,” he said.

But his recommendations stopped there. When Garner asked whether things like spinach, elderberry, or other supplements could help your immune system stay healthy, Dr. Fauci gave his honest opinion: "The answer, to the dismay of many, is no," he said.

Dr. Fauci isn’t shooting from the cuff here. “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, tells Health. The link between vitamin C and immune function is less clear for people who aren’t deficient in the vitamin, Dr. Adalja says. But, he adds, “it doesn’t hurt.” Here’s what you need to know.

How can vitamin D help boost your immune system?

Backing up a second here: Vitamin D, aka calciferol, is a fat-soluble vitamin that’s naturally present in a few foods, like fatty fish, beef liver, cheese, and egg yolks, per the National Institutes of Health Office of Dietary Supplements (NIH). It’s produced in your body when UV rays from the sun hit your skin and trigger what’s known as vitamin D synthesis.

Vitamin D can do a slew of different things in your body, including strengthen your bones, reduce inflammation, and help with immune function, the NIH says.

Here’s the big reason why vitamin D can be helpful as a supplement, per Dr. Adalja: Some people are deficient in it, meaning they don’t get enough of it on a regular basis. (An NIH data analysis specifically found that about 18% of people are at risk of having inadequate levels of vitamin D, while 5% are at risk of having an actual deficiency.)

As for the link with immune function, one systematic review and meta-analysis of data from 11,321 people published in the BMJ found that people took weekly or daily supplements of vitamin D were less likely to develop respiratory tract infections than those who didn’t. People who were the most deficient in vitamin D had the biggest benefit.

Another systematic review and meta-analysis of 5,660 people published in PLOS One found that vitamin D supplementation had a “protective effect” against respiratory tract infections, with a daily dose being the most effective.

How can vitamin C help boost your immune system?

While Dr. Adalja says that there’s “more data for vitamin D,” there is some research to support taking vitamin C supplements, too. In case you’re not familiar with it, vitamin C is a water-soluble vitamin that’s naturally present in some foods, like oranges, strawberries, broccoli, and tomatoes, per the NIH. Also known as L-ascorbic acid, it’s an antioxidant that “plays an important role in immune function,” the NIH says.

One review and meta-analysis conducted by researchers at Cochrane found that people who took vitamin C supplements when they had a cold had the infection reduced by 8% in adults and 14% in children. (That translated to about a day less of dealing with a cold.) People who took vitamin D supplements also had less severe colds than those who didn’t.

Vitamin C supplements may also help if you tend to exercise a lot. One Cochrane review looked at data on 642 marathon runners, skiers, and soldiers who took vitamin C supplements and found that taking anywhere from 250 milligrams to 1 gram a day of the vitamin reduced the risk of developing a cold by 50%.

So should you take vitamin D and vitamin C supplements?

It’s hard to make a blanket statement that everyone should take a particular supplement, but Richard Watkins, M.D., an infectious disease physician and professor of internal medicine at the Northeast Ohio Medical University, tells Health that these supplements are good for people to consider taking “in general.” And, he says, it’s reasonable for people to take vitamins D and C “in normal amounts” to try to boost your immune system.

Just so you know, the NIH recommends that most healthy adults strive to get 15 micrograms of vitamin D a day, while healthy women should strive to take 75 milligrams of vitamin C, and men should aim for 90 milligrams of the vitamin a day.

Of course, if you’re interested in taking a new supplement, it’s a good idea to check in with your doctor, just in case it could interfere with any other medications you’re taking. But, in general, experts say adding vitamins D and C supplements could be a great thing for your immune system.

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