10 supplements that ACTIVATE immune function and ward off viruses

A healthy diet is the best defense, find out the 10 superstars for boosting your immune system here, but these key supplements provide important backup.

Key Supplements

North American ginseng (also known as panax ginseng)

A Canadian study found that people who took a supplement of this gnarled root (and not its cousin, Siberian ginseng) for four months experienced fewer colds than those who took placebo. And when they did get sick, their symptoms were less severe and the colds resolved faster than the control group. Take: 200 to 400 mg per day as a preventative.

Vitamin D

A 2010 study by Yale researchers found that individuals with healthy levels of Vitamin D not only experience fewer respiratory tract infections than people who are deficient, but also get well faster when they do fall ill. As many as three out of four Americans have low levels of Vitamin D. Jennifer Johnson, ND, recommends supplementing with Vitamin D3, the form most readily accessible for use by the body. Take: 2,000 to 4,000 IUs per day of Vitamin D3 during the winter months.


Extracts of this berry were found in a 2009 study to block the H1N1 virus’s ability to infect host cells. Take: Elderberry extract in the widely available Sambucol Cold & Flu tablets or syrups. Follow package instructions at the first sign of infection.


Used for thousands of years in Traditional Chinese Medicine as an immune-booster, astragalus was also found by researchers at Memorial-Sloan Kettering Cancer Center to have one of the most beneficial effects (out of seven herbal medicines) on antibody production in mice. Take: 200 mg per day as a preventative measure.

Vitamin C

Despite its reputation as a cold and flu fighter (C promotes production of infection-fighting white blood cells), a 2009 review published in Journal of the American Academy of Nurse Practitioners found that mega-doses of this anti-oxidant did not reduce the number or severity of colds. But before you toss your C supplements, the review also found that regular supplementation could decrease the severity of symptoms once a cold has taken hold. “The best approach to C is to get enough of it on a daily basis and not rely on it to squash a cold,” says Beth Reardon, director of integrative nutrition at Duke Integrative Medicine. The best sources come from food—kiwi, green peppers, leafy greens, citrus, and strawberries, in particular—but if you don’t regularly eat a variety of fruits and vegetables, consider supplementing. Take: 1000 mg per day as a preventative measure.

What Not To Eat


“A lot of people start slamming orange juice when they feel a cold coming on, but they’re doing themselves a disservice,” says Beth Reardon, of Duke Integrative Medicine. Any fruit juice causes a spike in blood sugar, which cues inflammation and distracts your immune system from warding off infection, Reardon says. Instead, get your antioxidant fix from eating the fruit itself—the fiber in the fruit will prevent dramatic swings in blood sugar.

Mac ‘n’ Cheese

The rich comfort foods of winter may have something to do with the higher incidence of viruses in the cold months, as saturated fat appears to blunt immunity. A Tufts University study found that people placed on a low-fat diet saw a significant increase in their T cells, a key component of the immune system.


“White sugar and white flour are both inflammatory,” Reardon says. Meaning, eating them is the equivalent of giving your immune system busywork, which diverts resources from warding off bugs. Instead of a holiday cookie exchange, consider a healthy side dish swap, made with some of the immunity power players listed above.

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