As cold and flu season enters its wintry worst, fight back with these 10 super-immune boosting foods that can strengthen your system against pathogens and set you up for long-term immune health:
1. Yogurt is rich in probiotics, beneficial bacteria that improve the gut's immune system.
It's also high in calcium, another compound essential to a healthy immune system. Be sure your yogurt has a "live and active cultures" seal, and is free from sugar, flavorings, or additives. If you don't eat dairy, get your beneficial bugs from traditionally fermented sauerkraut, tempeh, natto, kimchi, or miso.
2. Oats, particularly oat bran, are high in beta-glucan, a source of fiber that may protect against viruses and other pathogens.
Some studies suggest a cancer-preventive effect of oat beta-glucans. Barley, nutritional yeast, and mushrooms are also rich in beta-glucans. If you're sensitive to gluten, choose gluten-free oats (oats are naturally free of gluten, but may be processed in a facility that also processes glutinous grains).
3. Oysters are rich in zinc, crucial for development of white blood cells that destroy bacteria and viruses.
Even mild deficiencies can increase the risk of infection. Because too much zinc has negative effects on the balance of other minerals, food-versus supplements-is the best way to get this important mineral. If you don't eat seafood, sesame seeds, pumpkin seeds, garbanzo beans, lentils, cashews, and quinoa are other good sources of zinc.
4. Brazil nuts are packed with selenium, an antioxidant that enhances immune response, improves resistance to viral infections, and may protect against cancer, especially prostate cancer.
Selenium is also abundant in tuna, lobster, shrimp, egg yolks, pumpkin seeds, and sunflower seeds. Because it can be toxic at high doses, don't overdo it-between six and eight Brazil nuts gives you about 500 mcg of selenium.
5. Pumpkin is loaded with beta carotene, an antioxidant that's converted by the body to vitamin A.
Vitamin A enhances white blood cell activity and other immune functions, and studies show even small deficiencies increase the risk of infectious disease. Carrots, papaya, cantaloupe, sweet potatoes, spinach, collards, and kale are also high in beta carotene.
6. Grapes are high in resveratrol, an antioxidant that supports immune function, especially when combined with vitamin D.
It also helps protect against cancer, especially lung and colorectal cancers. The best sources are red, purple, and black grapes and grape juice, but resveratrol is also found in peanuts, pistachios, blueberries, and cranberries.
7. Mushrooms contain immune-enhancing lentinan and other compounds that protect against viral infection and cancer.
Many studies have shown their effectiveness in treating HIV-infected patients, protecting against cancer, preventing tumor metastasis, and enhancing chemotherapy. Shiitake, reishi, and maitake mushrooms are the most potent sources, but button and crimini mushrooms are also effective.
8. Garlic is rich in allicin and sulfides, compounds that increase immune-system activity, fight off bacteria and viruses, and may protect against cancer.
In one study, people who ate six cloves of garlic per week had a 30 percent lower rate of colorectal cancer and a 50 percent lower rate of stomach cancer. It's best used fresh and raw, since the active ingredients dissipate within an hour of chopping or smashing.
9. Black tea is high in an amino acid called L-theanine, which appears to increase the body's levels of virus-fighting compounds.
In one study, tea drinkers had five times more L-theanine in their blood than coffee drinkers. Green tea also contains L-theanine, and is rich in epigallocatechin (EGCG), a powerful immune booster than can protect against cancer and inhibit tumor growth and metastasis.
10. Papaya is a great source of vitamin C, an antioxidant that has antimicrobial activity, improves immunity, and reduces the risk, severity, and duration of infectious disease.
Vitamin C may also protect against some cancers, including prostate and cervical cancer. You'll also get abundant C from leafy greens such as bell peppers, Brussels sprouts, oranges, broccoli, and pineapple.
In the 1600s and 1700s, British sailors were dying at sea from a then-unknown disease (which turned out to be scurvy). On one of these trips, a passenger named Dr. Roger Lind performed a nutritional experiment on the sailors and found that they felt better almost immediately after eating citrus fruits. This ultimately led to the discovery of vitamin C, the substance in citrus that is responsible for these health benefits. The British Royal Navy then made it a practice to supply lemon juice to all sailors, but ultimately switched to lime juice, leaving the British Navy with the nickname "limeys." Limes not only contain vitamin C, they also boast a number of flavonoids with both anticancer and antioxidant properties.