Aloe vera. Two ounces of the juice of this succulent, subtropical plant every two hours for up to 12 hours works as an anti-inflammatory to help relieve diarrhea, colitis or irritable bowel syndrome. As an alternative, you can take one-half to two teaspoons of freeze-dried aloe vera dissolved in water or juice daily. Applied topically, aloe vera gel speeds healing of sunburn, minor wounds and burns. Astragalus. This herb helps curb chronic colds, ear infections and the flu. It also helps restore immunity in cancer patients who have been affected by chemotherapy drugs. Typical dosage: One 500-mg capsule -- or about 15 drops of tincture daily. Berries. Blackberries, blueberries, cranberries and strawberries contain immunity-boosting anthocyanidins and other flavonoids. They also contain lots of dietary fiber and vitamin C -- both known cancer fighters. Carrots, sweet potatoes, tomatoes and yellow squash. Brightly colored vegetables contain carotenoids, compounds known to prevent cancers of the lung, colon, breast, uterus and prostate. Cruciferous vegetables. Broccoli, brussels sprouts, cabbage, cauliflower, collard greens and kale protect against breast, cervical and other cancers, according to studies at Rockefeller University in New York City and Johns Hopkins University School of Medicine in Baltimore . Garlic, onions, chives and leeks are loaded with sulfur compounds, which have potent antimicrobial and antifungal properties. These "allium" vegetables are effective against colds, flu, parasites, yeast overgrowth and stomach "bugs." Garlic may even help prevent and treat prostate cancer, according to research recently conducted at Memorial Sloan-Kettering Cancer Center in New York City . Typical dosage: One or two cloves of raw garlic a day. If you dislike garlic odor, take one to three capsules of freeze-dried garlic daily. Reputable brands: Enzymatic Therapy's Garlinase and Nature's Way Garlicin. Grapefruit seed extract. In addition to standard food-safety precautions, take 15 drops daily in a glass of juice upon arrival in an underdeveloped region to help prevent traveler's diarrhea. Important: Ask your doctor before taking grapefruit seed extract. It may interfere with some medications. Green tea. It contains polyphenols, antioxidant compounds that stop formation of nitrosamines, cancer-causing compounds produced in the stomach. Green-tea drinkers have low rates of pancreatic, esophageal, colon, stomach and lung cancers. Drink three to four cups or take two to four 500-mg capsules of green-tea extract daily. Nutritional supplements. In addition to vitamin C, consider taking these natural immunity boosters daily... Carotenoids (10,000 international units -- IU) Coenzyme Q-10 (50 mg) Lipoic acid (50 mg) Selenium (100 micrograms) Vitamin E (200 IU) Zinc (20 mg) Soy foods. Tofu, soymilk, tempeh and miso contain antioxidants and phytochemicals that help block tumor growth. Tofu, specifically, is believed to reduce the risk for prostate cancer.