Another popular flowering plant that's gaining more and more popularity in the U.S. food market recent years is elderberry, thanks to its ability to fight symptoms of the common cold and flu, allergies and inflammation. It's usually consumed as an extract, syrup or tea. "Research shows that consuming 15 milliliters of elderberry extract within the first 48 hours of onset of flu symptoms may lead to relief about 4 days earlier compared to placebo," says Dr. Axe.

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"In traditional medicine, the roots, stems and leaves of the ginseng plant have been used for maintaining immune homeostasis by regulating the immune cells," says Dr. Axe. "Ginseng also has antimicrobial properties and it works to defend the body against bacterial and viral infections." While you shouldn't have any trouble finding ginseng in tea form at your local supermarket, Dr. Axe recommends taking it in supplement form if tea isn't your thing. Take about 500 milligrams twice daily to score immune-boosting benefits as well as potential perks such as lowered blood sugar and cholesterol levels.

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If you're already a fan of this sulfur-containing bulb and love cooking dishes fragranced or spiced with it, you're doing your immune system some good. As Dr. Axe explains, garlic has long been touted for its cold and flu-busting attributes, and is likely why chicken soup is such a powerful cold-fighter. "Garlic contains selenium, an essential trace mineral that helps prevent cell damage," he says. When possible, try sneaking some garlic into your meals at least twice a day, in chicken soup, in stir-fries, etc.

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Since our body doesn't produce this immune system-regulating vitamin on its own, it's essential that we get it from food or the sun. Since the sun isn't the safest bet in the world (since its harmful UV rays can cause burns, wrinkles and skin cancer), it's best to turn to food as a source. Among the best vitamin D-rich foods to add to your diet, Largeman-Roth recommends eggs. "Two eggs contain 160 IU of D," she says. "Keep the yolks in — that's where the vitamin D and other important nutrients, like choline, are found." Additionally, mushrooms and fatty fish are other food sources of vitamin D. "Adults ages 19-50 require 600 IU of vitamin D daily, so getting at least one food source daily, plus supplemental vitamin D is smart," she adds.

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Zinc is not only vital for keeping your immune system strong, but it also helps wounds heal, according to Largeman-Roth. You can find it in red meat, including lamb, beef and bison, as well as in chicken, seafood, pork, fortified cereal, chickpeas, cheese, almonds and cashews. She recommends sneaking at least two zinc-packed foods daily to meet your needs, which are 11 mg per day for men and 8 mg per day for women. "Three ounces of beef has 7 mg of zinc, 3 ounces of lobster boasts 3.4 mg and chickpeas have 1.3 mg," she adds.

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