Fruits and vegetables with anti-cancer properties
Coming in contact with different types of environments, diets and disease causing pathogens results in alteration in the genetic constitution of the cells. This results in the development of cancer cells. It has been estimated that up to 80% of cases of cancer of colon, prostate and breast and about one third of all cancer cases can be linked to the lifestyle and the diet of the people concerned. With the advent of newer technologies, like the DNA chip technology, we have got the means to study about the intricate interactions between the different nutrients and the various genes. These studies help in the better understanding of the pathophysiological mechanisms which cause cancer which in turn helps us to identify the populations at risk.
The American Cancer Society (ACS) has listed various food items which help in preventing cancer. They include vegetables like broccoli, cabbage, eggplant, cauliflower, carrots, green beans, radish, soy red onions, tomatoes, sweet potatoes and yams.
Fruits with anti-cancer properties include blueberries, grapes, lemons, apricots, mangoes, papaya, ranges and grapefruit. It has been reported by the American Institute for Cancer Research (AICR) that these fruits and vegetables considerably reduce the growth of cancers.
Fruits and vegetables contain phenols, indols, flavones, cumines, and isothiocyanates. They check the carcinogens from reaching important specific cancer triggering sites inside the cells and thus act as natural blocking agents. The vegetables, especially of the ‘cruciferous family’ contain
1) sulforaphane which blocks the enzymes which facilitate the entry of carcinogens inside the cells,
2) indoles which reduce the chances of breast cancer,
3) compounds which act in the gut to stop the formation of nitrosamine which is carcinogenic,
4) phytochemicals which help the body in fighting against cancer. The phytoestrogens block the estrogen receptor sites on the cells and reduce the risk of breast cancer by almost 40%.
Beta carotene, vitamin C, E and D, and many other antioxidants to prevent cancer
Beta carotene, vitamin C, vitamin E and many other antioxidants present in fruits and vegetables are anti cancer in nature. They protect against cancer by guarding the cell membrane of the cells lining the gut and by preventing reactions in the gut which make its contents carcinogenic.
Beta carotene prevents the growth of tumors by making ‘tumor necrosis factor’ and by strengthening the immune system of the body. It is recommended in a dose of 15-20 mg per day.
Vitamin C hinders the formation of a carcinogen called ‘nitrosamine’ which is formed from nitrates and nitrites present in processed foods. It boosts the body’s ability to manufacture lymphocytes and thus improves the natural defense system of the body. It is present in ample amounts in citrus fruits. Consuming 1,000 to 2,000 mg of vitamin C per day is sufficient for its anti-cancer properties.
Another vitamin that has proved its forte as an anti-cancer compound is vitamin D. It has been known to decrease the incidence of cancers of colon, breast and prostrate. It stops the growth of the tumor by restraining the development of new blood vessels which nourish the tumor. Exposure to sunlight for 10-15 minutes per day is normally adequate to provide the necessary amount of vitamin D.
A high fiber and mineral diet is an important anti-cancer food
Apart from fruits and vegetables, a high fiber diet has been advocated as an important anti-cancer food. It is especially useful in people with a high hereditary risk of having colorectal polyps which are a known precursor to colon cancer. As the fiber in the diet is difficult to digest, it along with water reduces the concentration of carcinogens by making the stools bulky. It reduces the transportation time of the food in gut, thereby minimizing the time for carcinogens to get absorbed. It also binds with the carcinogens so that they cannot act on the cells lining the gut.
The bacteria in the gut act on the bile acids to produce ‘fecapentanes’, carcinogens which can cause mutation in the cells lining the gut. Fiber binds with the bile acids and prevents the production of fecapentanes. Fermentation of the fiber by the gut bacteria changes the pH of the intestine and reduces the toxicity of the bile acids. Thus fiber is an important constituent of the diet against colon cancer.
Fiber also reduces the re-absorption of estrogen from the intestine into the blood stream by binding with it. It thus plays an important role in the reduction of incidence of breast cancer.
Fiber is abundantly present in whole wheat, wheat bran, whole grains, kidney beans, navy beans, legumes and prunes. One should consume around 25 mg of fiber everyday.
Soy, belonging to the legume family, plays an important role against prostate and other hormone dependant cancers. It contains phytonutrients like isoflavones, which prevent ‘angiogenesis’, a process whereby new blood vessels which nourish the growing tumor are formed. It has an effect on the levels of various hormones and thus is important against prostate and breast cancer. It also prevents colon cancer by binding with the bile acids. Soy is present in milk products, tofu and vegetable burgers.
Fats with anticancer properties include monounsaturated fats present in vegetable oils like olive oil and canola oil and omega 3 fatty acids present in sea foods like salmon and tuna and in fish oil and flax seed oil. Omega 3 fatty acids blocks the effect of estrogen on breast cells thus reducing the incidence of breast cancer.
Minerals like calcium check the proliferation of the epithelial cells of the intestine, thereby reducing the chances of colorectal cancer. Calcium is present in milk and all dairy products, like yogurt and in bony fish.
Another mineral with antioxidant properties is selenium. It binds with the carcinogenic free radicals and reduces the incidence of colon cancer. The recommended daily dose of selenium is 100-200 mcg. Selenium is more effective when taken in conjunction with vitamin E.
Phytochemicals called ‘catechins’ present in green tea prevent the growth of tumor cells.
Foods that may increase the risk of cancer
The American Cancer Society (ACS) has discouraged some foods that may increase the risk of cancer. These are saturated fats, processed meat and alcohol. Besides, carbohydrates should be consumed in moderation because a diet too rich in them may lead to obesity which, in turn, may lead to cancer in some cases.
Saturated fat is rich in low density lipoproteins (LDL) which promote the growth of tumor cells. Hydrogenated fats interfere with the normal metabolic reactions of the cells making them precancerous. Bile acids, required in the digestion of fat, when produced in excessive quantity and allowed to stagnate in the large intestine, may be converted to ‘apcholic acid’, a known carcinogen. A high fat diet increases the production of these bile acids. So the fat intake should be less than 20% of the total calorie intake.
Processed meats contain nitrosamine, a known carcinogen. Other carcinogens, called as ‘heterocyclamines’, which can injure the DNA of the cells, are released on grilling the meat under high heat. They may lead to increased incidence of colon cancer.
Thus we can conclude that formulating strategies to prevent cancer should include research on the eating habits and changing the dietary patterns as required.