Oats and barley
These grains contain beta-glucan, a type of fiber with antimicrobial and antioxidant capabilities more potent than echinacea, reports a Norwegian study. (When consumed, the echinacea plant may slightly reduce your chances of catching a cold, according to the U.S. Department of Health & Human Services.) When animals eat this compound, they’re less likely to contract influenza, herpes, even anthrax; in humans, it boosts immunity, speeds wound healing, and may help antibiotics work better.
✔️ Your optimal dose: At least one of your three daily servings of whole grains.
This potent onion relative contains the active ingredient allicin, which fights infection and bacteria. In one study, British researchers gave 146 people either a placebo or a garlic extract for 12 weeks; the garlic takers were two-thirds less likely to catch a cold. Other research suggests that garlic lovers who chow more than six cloves a week have a 30 percent lower rate of colorectal cancer and a 50 percent lower rate of stomach cancer.
✔️ Your optimal dose: We know it’s a lot, but ideally you should aim for a clove or two a day. (Psst! These garlic-breath-remedies can help keep your breath fresh.)
Selenium—plentiful in shellfish such as oysters, lobsters, crabs, and clams—helps white blood cells produce cytokines, proteins that help clear flu viruses out of the body.
✔️ Your optimal dose: Two servings a week (if you’re pregnant or planning to be, you should ask your doctor about how much you need).
When University of Nebraska researchers tested 13 brands, they found that all but one (chicken-flavored ramen noodles) blocked the migration of inflammatory cells—an important finding, because cold symptoms are a response to the cells’ accumulation in the bronchial tubes. The amino acid cysteine, released from chicken during cooking, chemically resembles the bronchitis drug acetylcysteine, which may explain the results. The soup’s salty broth also keeps mucus thin the same way cough medicines do. Added spices, such as garlic and onions, can increase soup’s immune-boosting power.
✔️ Your optimal dose: Have a bowl when you’re feeling crummy. (Give this delicious chicken soup recipe a try!)
In a Harvard study, people who drank 5 cups a day of black tea for two weeks had 10 times more virus-fighting interferon in their blood than others who drank a placebo hot drink. The amino acid that’s responsible for this immune boost, L-theanine, is abundant in both black and green tea—decaf versions have it, too.
✔️ Your optimal dose: Several cups daily. To get up to five times more antioxidants from your tea bags, bob them up and down while you brew. (Try these soothing teas if you’re already dealing with a sore throat and cough.)
Zinc deficiency is one of the most common nutritional shortfalls among American adults, especially for vegetarians and those who’ve cut back on beef, a prime source of this immunity-bolstering mineral. And that’s unfortunate because even mild zinc deficiency can increase your risk of infection. Zinc in your diet is essential for the development of white blood cells, the intrepid immune system cells that recognize and destroy invading bacteria, viruses, and assorted other bad guys, says William Boisvert, PhD, an expert in nutrition and immunity at The Scripps Research Institute in La Jolla, CA.
✔️ Your optimal dose: A 3-oz serving of lean beef provides about 30 percent of the daily value (DV) for zinc. That’s often enough to make the difference between deficient and sufficient.
Not a beef person? Many fortified bowls of cereal pack an entire day’s worth of zinc. For example, a serving of Kellogg’s Smart Start or General Mills Whole Grain Total, has about 15 milligrams (mg) of the mineral. For a point of comparison, a 3-ounce serving of beef has about 7 mg of zinc.
✔️ Your optimal dose: Aim for one bowl daily—especially if you relate to any of these six signs you’re not getting enough zinc.
✔️ Your optimal dose: One medium cooked sweet potato (roughly 114 grams or 5 inches long) only packs about 100 calories and more than 100 percent of your daily recommended intake of vitamin A.
Along with orange produce, dark, leafy greens like kale are an excellent way to increase your vitamin A intake and bolster your immune function.
✔️ Your optimal dose: Toss a cup into salads, omelets, stir-fries and pasta dishes a few times a week. A serving has just 33 calories and more than a day’s worth of your recommended vitamin A intake.
There’s a reason you’re told to load up on vitamin C when you get sick: The nutrient is great for your skin, which acts as a barrier between your body and harmful organisms. On top of that, studies show that not getting enough vitamin C can actually impair your immune response and make you more susceptible to infections. While the jury is still out on whether or not vitamin C can truly prevent a cold, a 2017 review of research suggests supplementing with C can help stave off respiratory infections—or at the very least, help reduce the severity and length of your symptoms if you fall ill. Yes, citrus fruits like oranges are full of vitamin C—but bell peppers, strawberries, mango, kiwi, and broccoli pack a bigger punch.
✔️ Your optimal dose: Snack on a mix of peppers to get your crunchy fix. Just one cup of sliced red peppers delivers 117 milligrams (mg) of vitamin C—way beyond the recommended 75 mg for most adult women. Yellow bell peppers contain even more.
You already know that vitamin D is important for your bones, since it helps you absorb calcium properly—but it’s also essential for a healthy immune system. In fact, vitamin D deficiency or insufficiency (which affects an estimated 42 percent of Americans) may increase your chances of upper respiratory infections and even immune disorders such as multiple sclerosis, type 1 diabetes and Crohn’s disease, research shows. Why? Scientists have found that your immune cells actually have vitamin D receptors, which are important for regulating your body’s natural defense mechanisms.
While the sunshine vitamin is hard to come by naturally through your diet, foods high in vitamin D, like eggs, fish, and beef, or even fortified cereal and milk, can help you meet your daily intake. The NIH recommends a minimum of 600 international units (IUs) of vitamin D for most adults daily, but many other accredited organizations suggest aiming much higher.
✔️ Your optimal dose: One egg contains roughly 41 IUs of vitamin D, so scramble a few up for breakfast for one fifth of your daily recommended intake. (Just make sure you eat the whole egg, not just the whites!) Bonus: egg yolks also contain zinc and selenium for an extra immune-boosting punch.
For centuries, people around the world have turned to mushrooms for a healthy. Contemporary researchers now know why. “Studies show that mushrooms increase the production and activity of white blood cells, making them more aggressive. This is a good thing when you have an infection,” says Douglas Schar, DipPhyt, MCPP, MNIMH, the former director of the Institute of Herbal Medicine in Washington, DC. They’re also a great natural source of vitamin D.
✔️ Your optimal dose: Shiitake, maitake, and reishi mushrooms appear to pack the biggest immunity punch; experts recommend at least ¼-ounce to 1-ounce a few times a day for maximum immune benefits. Add a handful to pasta sauce, sauté with a little oil and add to eggs, or heap triple-decker style on a frozen pizza.
In an 80-day Swedish study of 181 factory employees, those who drank a daily supplement of Lactobacillus reuteri—a specific probiotic that appears to stimulate white blood cells—took 33 percent fewer sick days than those given a placebo. Though not every brand of kefir uses this specific strain, many Lifeway products do, including their Perfect12 and Lowfat Kefir beverages.
✔️ Your optimal dose: Try working kefir into your diet at least a few times per week.
Salmon, mackerel, and herring are rich in omega-3 fatty acids, which reduce inflammation, increasing airflow and protecting lungs from colds and respiratory infections. One animal study also found that the nutrient may help ward off various strains of the flu. Salmon is also another great source of vitamin D.
✔️ Your optimal dose: Consume two or three 4-ounce servings per week. If you’re pregnant or breastfeeding, avoid eating shark, swordfish, king mackerel, and tilefish, which are high in mercury. (Check out these delicious salmon recipes for some great ideas for preparing your next fish dinner.)