Dark green leafy vegetables such as kale contain minerals such as calcium and magnesium that can protect against cancer.
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Cancer is the second leading cause of death and accounts for one in four deaths in the United States. The American Cancer Society estimates that in 2012, more than 1.6 million people will receive a cancer diagnosis—a number that excludes skin cancers, which are so common they’re not reported to cancer registries. The group also reports that more than 577,000 Americans will die from cancer this year, a rate of more than 1,500 people a day.
Despite these disheartening statistics, cancer is a largely preventable disease. Genetics play a significant role in only a few cancers. Scientists attribute one-third of cancers to tobacco use, one-third to diet and one-third to environmental exposures (infectious microorganisms, ultraviolet light, radiation, pollutants and other toxins). Physical inactivity, obesity, insufficient sleep and alcohol are also linked to some cancers.
Prevention of many cancer risk factors is pretty straightforward: Stay away from tobacco, restrict alcohol intake, manage your weight, move your body and get enough sleep. Those changes prevent a host of illnesses and promote healthy longevity. Although it takes patience and perseverance, changing our habits is well worth it in terms of cancer prevention.
The Anti-Cancer Diet
Science is fairly certain that our diets play an important role in cancer prevention, but exactly how the two are linked is far from clear-cut. Most human cancer studies are observational, meaning they provide evidence for associations between various diets and cancer but don’t establish cause. In general, however, plant-based diets seem to help prevent cancer. Edible plants contain vitamins, minerals, fiber, healthy fats, and antioxidant and anti-inflammatory compounds. Some plant chemicals fight cancer cells directly, while others promote a healthy immune system, which helps reduce cancer risk.
A number of anti-cancer foods, spices and herbs stand out for their ability to fight this disease. Most are rich sources of flavonoids and carotenoids, which, among other functions, reduce oxidation (free radical damage) and inflammation—twin processes that promote chronic diseases, including cancer. Flavonoids belong to a broader chemical group called polyphenols, which provide multiple benefits for plants and those of us who eat them. Most foods and supplements that make health headlines—including fruits, vegetables, chocolate, tea and wine—are brimming with polyphenols.
Berries, cherries and grapes: These tasty, nutrient-dense fruits owe their deep, vibrant colors to flavonoids such as anthocyanins and proanthocyanins, which pack potent antioxidant, anti-inflammatory and anti-cancer effects. Red grapes also contain resveratrol, the same antioxidant found in red wine.
Complex carbs: Refined carbohydrates lead to spikes in blood sugar, insulin and insulin-like growth factors, which can stimulate tumor growth. But whole (unprocessed) grains, legumes and vegetables contain complex carbohydrates, which digest more slowly and contain fiber. Fiber may help bind potentially cancer-causing substances in the bowel, preventing their absorption into the bloodstream and helping to prevent colon cancer. Fiber consumption also supports healthy digestive microorganisms, which contribute to healthy immune function.
Cruciferous vegetables: This plant family, which includes broccoli, cauliflower, cabbage, rapini, mung beans, alfalfa sprouts and Brussels sprouts, among others, contains glucosinolates, compounds the body breaks down into anti-cancer substances. Animal and population studies link increased consumption of cruciferous vegetables with reduced cancer risk. Studies have found broccoli to be especially effective in fighting certain types of cancer.
Dark green leafy vegetables: Kale, collards, mustard greens, bok choy, arugula, watercress and maca are natural sources of minerals such as calcium and magnesium, both of which may protect against colon cancer. Women who eat more leafy greens have a reduced risk of breast cancer. Dandelion (Taraxacum officinale) and stinging nettle (Urtica dioica) brim with vitamins and minerals. Preliminary research suggests they also have anti-cancer activity. Note: Nettles must be cooked, dried or blended (as in a smoothie) to remove their sting. You can also obtain anti-cancer benefits from dried nettle and dandelion greens in the form of tea. Simply add one tablespoon herb per cup hot water, steep 15 minutes, strain and drink.
Seeds and nuts: These healthful snack foods contain vitamins, minerals, healthy fats and fiber. Increased consumption correlates with a reduced risk of certain cancers, particularly colon cancer. Flax seeds, sesame seeds, sunflower seeds and pumpkin seeds contain lignans, which our intestinal bacteria can convert into phytoestrogens (plant estrogens). Flax seeds, the richest source of lignans, may inhibit the growth of breast, colon and prostate cancer. Regular consumption of pumpkin and sunflower seeds has been linked with a reduced risk of breast cancer. Walnuts may also inhibit colon and breast cancer.
Tomatoes and tomato products are an excellent source of dietary carotenoids. They owe their red color to lycopene. Research associates regular consumption of tomatoes and tomato products with a reduced risk of prostate cancer and possibly breast cancer. Even a single serving of tomatoes or one tomato product a day may help protect DNA from damage. It’s best to obtain lycopene via your diet—whether lycopene supplements protect against cancer is controversial.
Legumes: In addition to being fiber-rich, legumes contain phytoestrogens. Soybeans contain a particularly rich source of phytoestrogens called isoflavones. While estrogen has been implicated in the development of breast and uterine cancer, phytoestrogens have much weaker stimulatory effects, and population studies link consumption of soy foods with a reduced incidence of breast, uterine, ovarian, prostate and colon cancer. Soy consumption also decreases growth factors that increase breast cancer risk.
One concern has been whether isoflavones present a risk for breast cancer survivors. Reassuringly, a large study of Chinese and American women found that soy food consumption correlated with a reduced risk of recurrence. While soy foods seem to be beneficial, some experts discourage against supplementing with soy protein or soy isoflavones.
Orange fruits and vegetables are rich in plant pigments called carotenoids, which protect against several types of cancer including prostate, breast, cervical, lung, ovarian, pancreatic, and gastrointestinal. Non-vitamin A carotenoids (lycopene, lutein, astaxanthin and zeaxanthin) protect against DNA damage. Orange vegetables (carrots, pumpkin, sweet potatoes, winter squash), orange fruits (cantaloupe, mangos, apricots, guava, goji berries) and the leafy greens mentioned earlier are all good sources of carotenoids.
Pomegranate extracts have been shown to inhibit the growth of breast, prostate, colon and lung cancers in cell cultures and animal studies. Extracts also protect against ultraviolet light-induced skin cancer. All parts of the pomegranate fruit—rind, pith and juicy seeds—have valuable chemicals and are edible. The seeds taste delicious alone, in salads and atop yogurt. However, the rind and pith, while edible, are bitter. Juice the whole fruit in a commercial juicer to benefit from the rind and pith’s active chemicals. You can also eat the pith whole or infuse water with the rind to make a tea.
Herbs for Cancer
Garlic: Research shows that garlic (Allium sativum) has cancer-protective effects. Garlic enhances enzymes that detoxify carcinogens, quench oxidation, inhibit proliferation of cancer cells, induce cancer cell death and boost immunity. However, heat deactivates some of garlic’s key ingredients. To maximize benefits, add raw garlic to dressings, dips, soups and sauces. You can also retain more of garlic’s anti-cancer effects when cooking by crushing it and allowing it to sit for 10 minutes (which allows time for critical enzymatic changes) before adding it to the pan.
Medicinal mushrooms: Mushrooms contain polysaccharides and other ingredients that both enhance immunity and have anti-cancer properties. Most research has been done on medicinal mushrooms such as reishi, shiitake, maitake and cordyceps. However, all edible mushrooms have benefits. Even the common button mushroom enhances immune-cell functions and can fight cancer. Women who regularly eat mushrooms have a reduced risk of breast cancer. Note: Some mushrooms (reishi and cordyceps, for example) are too rare or woody to find in grocery stores. Look for supplements containing these mushrooms.
Milk thistle: While better known for protecting the liver, milk thistle (Silybum marianum) also has cancer-protective effects. It contains an antioxidant, anti-inflammatory flavonoid complex called silymarin. Research shows that it promotes the repair of DNA, blocks angiogenesis and suppresses proliferation and metastasis in a variety of cancers. Milk thistle is available as a tincture or standardized extract. You can also use the ground seeds in tea or sprinkle them atop foods. Milk thistle’s delicious relative, the artichoke, also contains polyphenols.
Tea: Black, green and oolong tea all come from the same plant—Camellia sinensis. Studies link tea consumption with a reduced risk of gastrointestinal, pancreatic, bladder, prostate, ovarian, uterine and breast cancer. Green tea is particularly rich in a polyphenol called epigallocatechin gallate. In lab research, it has inhibited cancer cell formation, proliferation, invasiveness and metastasis, and provokes cancer cell death. Animal studies show protection against many cancers, including skin cancer. Try to drink three to five cups of green tea a day.
Turmeric: Turmeric (Curcuma longa) contains potent antioxidant and anti-inflammatory substances. Curcumin, a key chemical in turmeric, can inhibit cancer cell growth and migration, block the creation of blood vessels to the cancer and induce cancer cells to die. The optimal dose for supplemental curcumin isn’t clear, though doses up to 8 grams a day seem to be safe. Curcumin’s bioavailability—the amount the body can absorb—is low. Combining curcumin with bromelain (an enzyme in pineapple), piperine from pepper, or phosphatidylcholine, a chemical in foods like eggs, soybeans and mustard, seems to enhance absorption. In a boon for lovers of spicy foods, one of the most effective ways to consume turmeric may be in curry. Curried foods contain pepper and oil, which improve curcumin’s absorption.
Linda B. White is a freelance writer who also teaches in the Integrative Therapeutic Practices Program at Metropolitan State University of Denver.