Beans

Beans (also known as legumes) include lentils and peas along with many other varieties. Soybeans fall into this category as well; their anti-cancer benefits are described in full in the soy section.

The active ingredients in beans that scientists believe may play a role in cancer prevention include: saponins, protease inhibitors and phytic acid. These compounds, called phytochemicals, are found naturally in plants and appear to protect our cells from damage that can lead to cancer.

In laboratory studies, saponins have shown the ability to inhibit the reproduction of cancer cells and slow the growth of tumors in several different tissues. Protease inhibitors have slowed the division of cancer cells and helped to prevent tumors from releasing substances called proteases that destroy nearby cells. Phytic acid has shown the ability to significantly slow the progression of tumors.

Beans are also rich in fiber. AICR's second expert report,Nutrition, Physical Activity, and the Prevention of Cancer: A Global Perspective, found probable evidence that foods containing dietary fiber, like beans, can decrease one’s risk of developing colorectal cancer.

Berries

Berries are good sources of vitamin C and fiber. According to AICR's second expert report, Food, Nutrition, Physical Activity, and the Prevention of Cancer: a Global Perspective, foods high in vitamin C probably protect against cancer of the esophagus, while foods containing dietary fiber probably decrease colorectal cancer risk.

All berries, but particularly strawberries and raspberries, are rich in ellagic acid. In laboratory studies, this phytochemical has shown the ability to prevent cancers of the skin, bladder, lung, esophagus and breast. Research suggests that ellagic acid seems to utilize several different cancer-fighting methods at once: it acts as an antioxidant, it helps the body deactivate specific carcinogens and it helps slow the reproduction of cancer cells.

Strawberries also contain a wide range of other phytochemicals, called flavonoids, each of which seems to employ a similar array of anti-cancer strategies.

Blueberries contain a family of phenolic compounds called anthocyanosides, which many scientists believe are among the most potent antioxidants yet discovered.

Dark Green Leafy Vegetables

Spinach, kale, romaine lettuce, leaf lettuce, mustard greens, collard greens, chicory and Swiss chard are excellent sources of fiber, folate and a wide range of carotenoids such as lutein and zeaxanthin, along with saponins and flavonoids.

According to AICR's second expert report, Food, Nutrition, Physical Activity, and the Prevention of Cancer: A Global Perspective, foods containing carotenoids probably protect against cancers of the mouth, pharynx and larynx.

Researchers believe that carotenoids seem to prevent cancer by acting as antioxidants – that is, scouring potentially dangerous “free radicals” from the body before they can do harm. Some laboratory research has found that the carotenoids in dark green leafy vegetables can inhibit the growth of certain types of breast cancer cells, skin cancer cells, lung cancer and stomach cancer.

The Second Expert Report also noted probable evidence that foods containing folate decrease risk of pancreatic cancer and that foods containing dietary fiber probably reduce one’s chances of developing colorectal cancer.

Garlic

Garlic belongs to the family of vegetables called Allium, which also includes onions, scallions, leeks and chives. According to AICR's second expert report, Food, Nutrition, Physical Activity, and the Prevention of Cancer: A Global Perspective, foods belonging to the allium family of vegetables probably protect against stomach cancer. Moreover, the evidence in the report shows that garlic, in particular, probably decreases one’s chances of developing colorectal cancer.

The protective effect of garlic was shown to have a dose response relationship. In other words, highest exposure to the food showed the greatest decrease in risk. For cancer protection, AICR experts suggest including garlic as part of a well-balanced predominantly plant-based diet.

These allium vegetables contain many substances now being studied for their anti-cancer effects, such as quercetin, allixin and a large group of organosulfur compounds that includes allicin, alliin and allyl sulfides. In laboratory studies, components of garlic have shown the ability to slow or stop the growth of tumors in prostate, bladder, colon and stomach tissue.

Laboratory research has also shown that one garlic component, called diallyl disulfide, exerts potent preventive effects against cancers of the skin, colon and lung. Recently, this compound proved able to kill leukemia cells in the laboratory. A compound derived from garlic called ajoene has displayed similar activity.

In animal studies, components in Allium vegetables have slowed the development of cancer in several stages and at various body sites: stomach, breast, esophagus, colon and lung.

Grapes and Grape Juice

Both grapes and grape juice are rich sources of resveratrol, a type of natural phytochemical that belongs to a much larger group of phytochemicals called polyphenols.

The skin of the grape contains the most resveratrol, and red and purple grapes contain significantly more resveratrol than green grapes. Grape jam and raisins contain much smaller amounts of this phytochemical. Red wine also contains resveratrol. However, with AICR’s second expert report noting convincing evidence that alcohol is associated with increased risk for cancers of the mouth, pharynx and larynx, esophagus, breast (pre- and postmenopausal) and colon and rectum (in men), wine is not a recommended source of resveratrol.

Studies suggest that polyphenols in general and resveratrol, in particular, possess potent antioxidant and anti-inflammatory properties. In laboratory studies, resveratrol prevented the kind of damage known to trigger the cancer process in cell, tissue and animal models.

Other laboratory research points to resveratrol’s ability to slow the growth of cancer cells and inhibit the formation of tumors in lymph, liver, stomach and breast cells. Resveratrol has also triggered the death of leukemic and colon cancer tumors.

In one series of studies, resveratrol blocked the development of skin, breast and leukemia cancers at all three stages of the disease (initiation, promotion and progression).

Green Tea

Since ancient times, tea has been used as both beverage and medicine. Both black and green teas contain numerous active ingredients, including polyphenols and flavonoids, which are potent antioxidants.

One class of flavonoids called catechins has recently become the focus of widespread study for their anti-cancer potential. Tea is the best source of catechins in the human diet, and green tea contains about three times the quantity of catechins found in black tea.

In laboratory studies, green tea has been shown to slow or completely prevent cancer developent in colon, liver, breast and prostate cells. Other studies involving green tea have shown similar protective effects in tissues of the lung, skin and digestive tract.

Studies that track the diets of human subjects over several years (particularly studies conducted in Asia, where green tea consumption is common) have also associated regular usage of green tea with lower risk for bladder, colon, stomach, pancreatic and esophageal cancers.

AICR’s second expert report, Food, Nutrition, Physical Activity, and the Prevention of Cancer: A Global Perspective, was unable to make a recommendation regarding the relationship between tea consumption and cancer risk due to insufficient evidence.

Note: Very high amounts of green tea components (usually associated with overdosage of green tea supplements) have been shown to interact with drugs that affect blood clotting such as aspirin and change the way the body metabolizes certain medications.

Soy

Soybeans are a type of legume, or bean. Foods made from soybeans include tofu, soymilk, soybeans, soynuts, miso (soy paste), tempeh, soy burgers and soynut butter.

Scientists believe that several active ingredients in soy may have anti-cancer effects. These include: isoflavones (which have been studied most), saponins, phenolic acids, phytic acid, phytosterols, and protein kinase inhibitors.

Soy appears to contain some components that resemble very weak forms of the body’s natural hormones. As a result, soy foods can mimic the actions of hormones under certain conditions and counteract these hormonal actions at other times. Because of such complexities, most of the studies that have investigated soy’s role in cancer development have dealt with hormone-related cancers such as those of the breast and prostate.

Soy has been shown to inhibit the growth of prostate cancer cells in a variety of laboratory conditions. Soy has also been associated with the inhibition of breast cancer cells in some, but not all, laboratory experiments. Diets rich soy have been shown to alter the metabolism of breast tissue in animal subjects in ways that may translate into added anti-cancer protection.

Several human and laboratory studies suggest that consuming soy early in life (such as adolescence) may help protect against breast cancer later in life. Results are less encouraging when soy is consumed later in life.

As a general rule of thumb, soy seems to be a good food to include in your diet (along with other beans) as a source of protein and nutrients.  But, there's limited evidence in U.S. populations supporting hopes that soy food might offer special protection against breast cancer.

Current research shows that it is safe to eat moderate amounts of soy foods (e.g., soymilk, tofu), up to two to three servings per day.As a precaution, women receiving anti-estrogen treatments such as tamoxifen, should minimize soy foods and avoid isoflavone supplements.

Tomatoes

The tomato’s red hue comes chiefly from a phytochemical called lycopene. Tomatoes have attracted particular attention from prostate cancer researchers because lycopene and its related compounds tend to concentrate in tissues of the prostate.

AICR's second expert report, Nutrition, Physical Activity, and the Prevention of Cancer: A Global Perspective, found substantial and convincing evidence that foods containing lycopene probably protect against prostate cancer.

In animal models, consumption of tomato compounds has been linked to large decreases in prostate cancer risk. Moreover, there is evidence that this cancer-fighting potential is increased if tomatoes are consumed in a processed form that allows these natural compounds to be released and more easily absorbed, such as tomato sauce, tomato paste or tomato juice.

Lycopene, a powerful antioxidant, together with a group of related compounds collectively called the “red family,” has displayed anti-cancer potential in a variety of laboratory studies. In the laboratory, tomato components have stopped the proliferation of several other cancer cells types, including breast, lung, and endometrial.

Although the evidence suggests it is likely that foods containing lycopene, including tomatoes, offer cancer protection, AICR stresses the importance of eating a variety of plant foods to ensure the most protection against cancer development. No food in isolation can effectively lower cancer risk.

Whole Grains

The term “whole grain” means that all three parts of the grain kernel (germ, bran and endosperm) are included. Refined grains usually have the bran and germ removed, leaving only the starchy endosperm. Brown rice is a whole grain, white rice is not. Other whole-grain foods include wheat breads, rolls, pasta and cereals; whole grain oat cereals such as oatmeal, popcorn, wild rice, tortilla and tortilla chips, corn, kasha (roasted buckwheat) and tabouleh (bulghur wheat).

Whole grains are rich in fiber, vitamins, minerals and hundreds of natural plant compounds, called phytochemicals, which protect cells from the types of damage that may lead to cancer. In addition research points to specific substances in whole grains that have been linked to lower cancer risk, including antioxidants, phenols, lignans (which is a kind of phytoestrogen) and saponins.

AICR's second expert report, Nutrition, Physical Activity, and the Prevention of Cancer: A Global Perspective, found probable evidence that foods containing dietary fiber, like whole grains, can decrease one’s risk of developing colorectal cancer.

Moreover, limiting energy dense foods and eating a predominantly plant-based diet rich in vegetables, fruits, whole grains and beans can help with weight maintenance and, in turn, may decrease your risk of developing cancer.

Cited from AICR.org