Thomas Prychitko. The Gale Encyclopedia of Diets: A Guide to Health and Nutrition. Editor: Jacqueline L Longe. Volume 1. Detroit: Gale, 2008.
It appears more than ever, that there is a great deal of truth to the philosophy of eating fruits and vegetables to maintain optimum health. It is not only because of the nutrients they contain in the form of vitamins and minerals, also because of the chemicals found in these foods. Scientists continue to extensively study the nutrient quality and quantity of foods we consume. Although scientists are still not certain about the specifics, they’re beginning to close in on the healthful constituents of plant-based foods. In particular, they’re looking closely at two components: phytochemicals and antioxidants The goal is to determine precisely how and why these substances in fruits and vegetables can prevent or stop the development of tumors and cancer When animals are given vegetables and fruits before being exposed to carcinogen (cancer-causing agents), they are less likely to develop cancer. Although additional experimental data needs to be collected in humans, there is evidence to suggest that consuming generous amounts of fruits and vegetables plays an important role in preventing cancer.
Phytochemicals, are plant chemicals that are naturally occurring substances in plants. Several hundred types of phytochemicals have been identified, but many more likely remain to be identified. Some examples include indoles in cabbage or cauliflower, saponins in peas and beans, genstain in soybeans and isoflavones in soy milk and tofu. Over the past 20 years, nutrition scientists have consistently found that individuals that eat greater amounts of vegetables and fruits have lower rates of cancer. It has been only recently that the mechanism(s) by which phytochemicals assist the body in resisting cancer have begun to be understood. The phytochemicals present in fruits and vegetables protect the body by stunting the growth of malignant cells. Investigators have only an inkling of how many phytochemicals exist and how they work. They are confident, however, that an individual can get a basketful of anti-cancer nutrients by mixing and matching at least five servings a day of fruits and vegetables with seven or more starchy or protein-rich plant foods such as grains, peas and beans, and potatoes.
Supplements containing vitamins and minerals can help an individual gain some of the benefits of these substances. However, vitamin and mineral supplements are not a total replacement for real food.
This is because vitamin and mineral supplements, though very beneficial, do not supply the thousands of phytochemicals that might be present in fruits and vegetables, according to the Cleveland Clinic Foundation in Ohio. For example, eating a sweet potato with its skin, which is a great source of both beta carotene and fiber, provide at least 5,000 phytochemicals that are not present in a beta carotene supplement. That’s an extremely important difference. Isolating a few compounds in a pill will not provide you with the hundred of protective benefits that plant food provide. The best advice is to obtain phytochemicals by eating a good variety of plant foods every day. Whether fruits and vegetables are consumed in raw or cooked form does not really matter with regard to phytochemical content. Even canned, frozen and juiced fruits and vegetables pack a phytochemical punch. However, raw or steamed vegetables would provide the best nutrient value.
The antioxidants found in fruits, vegetables, and other plant-based foods fight free radicals, which are compounds in the body that attack and destroy cell membranes. The uncontrolled activity of free radicals is believed to cause many cancers. Examples of antioxidants include carotenoids, such as beta carotene, lycopene, and vitamins C and E.
The carotenoids, in particular, which give fruits and vegetables their bright yellow, orange, and red colors, are now gaining recognition for their nutritional worth. Numerous studies have extolled the virtues of lycopene (the carotenoid that makes tomatoes red) in preventing prostate cancer. One such study at Harvard University found that men who include tomato products in their meals twice a week could reduce their risk of developing prostate cancer by one-third compared with men who do not consume tomatoes.
Other lycopene-rich foods, such as watermelon, red grapefruit, and guava, are now piquing the interest of researchers. Watermelon not only yields more lycopene per serving (15 mg in 11/2 cups) than raw tomatoes (11 mg per 11/2 cups), but it’s also a rich source of vitamins A and C.
Whether antioxidants can reduce the incidence of cancer is still uncertain at this point because of the lack of sufficient studies. However, research data obtained thus far indicates that antioxidants do appear to provide health benefits.
The National Cancer Institute estimates that roughly one-third of all cancer deaths may be diet related. Scientists have recently estimated that approximately 30 to 40% of all cancers could be averted if people ate more fruits, vegetables, and plant-based foods and minimized high-fat, high-calorie edibles that have scant nutritional value. What you eat can hurt you, but it can also help you. In the past, researchers had linked fat consumption with the development of cancers, but they currently believe that eating fruits, vegetables, and grains may be more important in preventing the disease than not eating fat. Many of the common foods found in grocery stores or organic markets contain cancer-fighting properties, from the antioxidants that neutralize the damage caused by free radicals to the powerful phytochemicals that scientists are just beginning to explore. There isn’t a single element in a particular food that does all the work. The best thing to do is eat a variety of foods.
There are a number of foods that have been demonstrated to have the ability to help stave off cancer and some can even help inhibit cancer cell growth or reduce tumor size. The following is a list of foods that because of the nutrients they contain, have been determined to be the best cancer fighters:
Avocados: They are rich in glutathione, a powerful antioxidant that attacks free radicals in the body by blocking intestinal absorption of certain fats They also supply even more potassium than bananas and are a strong source of vitamin E Scientists also believe that avocados may also be useful in treating viral hepatitis (a cause of liver cancer), as well as other sources of liver damage.
Beans: Beans contain a number of phytochemicals, which have been shown to prevent or slow genetic damage to cells. While this makes beans beneficial for helping to reduce your risk of many types of cancer, specific research has suggested they are especially potent in preventing prostate cancer. As an added bonus, the high fiber content of beans has been connected with a lower risk of digestive cancers.
Berries: The two most widely studied cancer-fighting compounds in berries are ellagic acid (richest in strawberries and raspberries) and anthocyanosides (richest in blueberries). Ellagic acid is believed to help prevent skin, bladder, lung, and breast cancers, both by acting as an antioxidant and by slowing the reproduction of cancer cells. The anthocyanosides in blueberries are currently the most powerful antioxidants known to scientists and are beneficial in the prevention of all types of cancer. Raspberries contain many vitamins, minerals, plant compounds and antioxidants known as anthocyanins that may protect against cancer. According to a recent research study reported by Cancer Research, rats fed diets of 5% to 10% black raspberries saw the number of esophageal tumors decrease by 43% to 62%. A diet containing 5% black raspberries was more effective than a diet containing 10% black raspberries. Research reported in the journal Nutrition and Cancer in May 2002 shows black raspberries may also thwart colon cancer. Black raspberries are rich in antioxidants, thought to have even more cancer-preventing properties than blueberries and strawberries.
Cabbage, and cauliflower: All cruciferous vegetables including cabbage and cauliflower, are rich in a variety of compounds that have been shown to slow cancer growth and development in a number of laboratory studies. These vegetables contain a chemical component called indole-3-carbinol that can combat breast cancer by converting a cancer-promoting estrogen into a more protective variety. Other larger human studies have shown that cruciferous vegetables can help to reduce the risk of lung, prostate, and bladder cancers.
Broccoli: Broccoli, which is also a cruciferous vegetable, contains the phytochemical sulforaphane, a product of glucoraphanin, that is believed to aid in preventing some types of cancer, like stomach, colon and rectal cancer. Sulforaphane induces the production of certain enzymes that can deactivate free radicals and carcinogens. The enzymes have been shown to inhibit the growth of tumors in laboratory animals. However, be aware that the Agriculture Department studied 71 types of broccoli plants and found a 30-fold difference in the amounts of glucoraphanin. It appears that the more bitter the broccoli is, the more glucoraphanin it has. Broccoli sprouts have been developed under the trade name Brocco Sprouts that have a consistent level of sulforaphane that is as much as 20 times higher than the levels found in mature heads of broccoli.
Carrots: They contain a plentiful amount of beta carotene, which may help reduce a wide range of cancers including lung, mouth, throat, stomach, intestine, bladder, prostate and breast. Some research indicated beta carotene may actually cause cancer, but this has not proven that eating carrots, unless in very large quantities i.e. 2 to 3 kilos a day, can cause cancer. In fact, a substance called falcarinol that is found in carrots has been found to reduce the risk of cancer, according to researchers at Danish Institute of Agricultural Sciences (DIAS). It has been demonstrated that isolated cancer cells grow more slowly when exposed to falcarinol. This substance is a polyacethylen.
Chili peppers and jalapenos: They contain a chemical, capsaicin, which may neutralize certain cancercausing substances called nitrosamines and may help prevent cancers such as stomach cancer.
Cruciferous vegetables – broccoli, cauliflower, kale, Brussels sprouts, and cabbage contain two antioxidants, lutein and zeaxanthin that may help decrease prostate and other cancers.
Dark Green Leafy Vegetables: Leafy-green vegetables-like romaine lettuce, mustard greens, chicory, and Swiss chard-are rich sources of antioxidants called carotenoids. These compounds scavenge dangerous free radicals from the body before they can promote cancer growth. The vegetables are also rich in folate, a vitamin shown to reduce the risk of lung and breast cancer.
Figs: Apparently figs contain a derivative of benzaldehyde. It has been reported by investigators at the Institute of Physical and Chemical Research in Tokyo that benzaldehyde is highly effective at shrinking tumors, though further experiments need to be conducted. In addition, the U.S. Department of Agriculture says figs, which contain vitamins A and C, and calcium, magnesium and potassium, may curtail appetite and improve weight-loss efforts. Fig juice is also a potent bacteria killer in test-tube studies.
Flax: Flax contains lignans, which may have an antioxidant effect and block or suppress cancerous changes. Flax is also high in omega-3 fatty acids, which are thought to protect against colon cancer and heart disease. Flaxseed in the form of oil and meal contains phytoestrogens believed to reduce the risk of breast, skin, and lung cancer. Research on the potency of flaxseed as an anti-cancer food is still ongoing. A specialized diet called the Budwig diet, which has been used by some cancer patients, uses the combination of flax seed oil and cottage cheese. When these two foods are consumed simultaneously, it is said that they increase the levels of substances called phosphatides and lipoproteins in the blood. Dr. Johanna Budwig, the creator of the diet claims that the diet is both preventative and curative in regard to cancer.
Garlic: This herb has immune-enhancing allium compounds (dialyl sultides) that appear to increase the activity of immune cells that fight cancer and indirectly help break down cancer causing substances.
These substances also help block carcinogens from entering cells and slow tumor development. Diallyl sulfide, a component of garlic oil, has also been shown to render carcinogens in the liver inactive. Studies have linked garlic as well as onions, leeks, and chives to lower risk of a variety of cancers including stomach, colon, lung and skin cancer. Dr. Lenore Arab, professor of epidemiology and nutrition at the UNC-CH (University of North Carolina at Chapel Hill) schools of public health and medicine and colleagues analyzed a number of studies and reported their findings in the October 2000 issue of the American Journal of Clinical Nutrition. According to the report, individuals who consume raw or cooked garlic regularly face about half the risk of stomach cancer and two-thirds the risk of colorectal cancer as individuals who eat little or none. Their studies did not show garlic supplements had the same effect. It is believed garlic may help prevent stomach cancer because it has anti-bacterial effects against a bacterium, Helicobacter pylori, found in the stomach and known to promote cancer there.
Grapefruits: Like oranges and other citrus fruits, grapefruits contain monoterpenes, that are believed to help prevent cancer by sweeping carcinogens out of the body. Some studies show that grapefruit may inhibit the proliferation of breast-cancer cells in vitro. Grapefruits also contain vitamin C, beta-carotene, and folic acid.
Grapes: Particularly red and purple grapes, are a rich source of resveratrol, a potent antioxidant and anti-inflammatory agent, which inhibits the enzymes that can stimulate cancer-cell growth and suppress immune response. Resveratrol is thought to work by preventing cell damage before it begins. Grapes also contain ellagic acid, a compound that blocks enzymes that are necessary for cancer cells. Ellagic acid also appears to help slow the growth of tumors. Red grapes also contain bioflavonoids, which are powerful anti-oxidants that work as cancer preventives.
Kale: This cruciferous vegetable contains indoles, which are a nitrogen compound that may help stop the conversion of certain lesions to cancerous cells in estrogen-sensitive tissues. In addition, isothiocya-nates, phytochemicals found in kale, are thought to suppress tumor growth and block cancer-causing substances from reaching their targets.
Licorice root: It has a chemical, glycyrrhizin, that blocks a component of testosterone and therefore may help prevent the growth of prostate cancer. However, excessive amounts can lead to elevated blood pressure.
Mushrooms: There are a number of mushrooms that appear to help the body fight cancer and build the immune system. They include Shiitake, maitake, reishi, Agaricus blazei Murill, and Coriolus Versicolor. The active ingredient in medicinal mushrooms are polysac-charides called beta-glucans. These beta-glucans are powerful compounds that help in building immunity. Examples of beta-glucans include Lentinan and a unique beta-glucan called D-fraction, that is found in the Maitake mushroom. This D-fraction is believed to be responsible for the many health benefits of Maitake. These mushrooms also have a protein called lectin, which attacks cancerous cells and prevents them from multiplying. They also contain Thioproline. These mushrooms can stimulate the production of interferon in the body. Extracts from mushrooms have been successfully tested in recent years in Japan as an adjunct to chemotherapy.
Nuts: Many nuts contain the antioxidants quercetin and campferol that may suppress the growth of cancers. Brazil nuts contain 80 micrograms of selenium, which is important for those with prostate cancer.
Oranges and lemons: They both contain Iimonene which stimulates cancer-killing immune cells like lymphocytes that may also function in breaking down cancer-causing substances.
Papayas: They have vitamin C that works as an antioxidant and may also reduce absorption of cancer-causing nitrosamines from the soil or processed foods. Papaya contains folacin (also known as folic acid), which has been shown to minimize cervical dysplasia and certain cancers.
Red wine: Even without alcohol, red wine has polyphenols that may protect against various types of cancer. Polyphenols are potent antioxidants, compounds that help neutralize disease-causing free radicals. Also, researchers at the University of North Carolina’s medical school in Chapel Hill found the compound resveratrol, which is found in grape skins. It appears that resveratrol inhibits cell proliferation and can help prevent cancer. However, the findings didn’t extend to heavy imbibers, so it should be used in moderation. In addition, alcohol can be toxic to the liver and to the nervous system, and many wines have sulfites, which may be harmful to your health. Since some research indicates that alcohol is considered a class “A” carcinogen that can actually cause cancer, it is probably best to consume non-alcoholic wines.
Rosemary: This herb may help increase the activity of detoxification enzymes. An extract of rosemary, termed carnosol, has inhibited the development of both breast and skin tumors in animals. We haven’t found any studies done on humans. Rosemary can be used as a seasoning and it can also be consumed as a tea.
Seaweed and other sea vegetables: They contain beta-carotene, protein, vitamin B12, fiber, and chlorophyll, as well as chlorophylones, which are important fatty acids that may help in the fight against breast cancer. Many sea vegetables also have high concentrations of the minerals potassium, calcium, magnesium, iron, and iodine.
Soy products like tofu: These contain several types of phytoestrogens which are weak, nonsteroidal estrogens that resemble some of the body’s natural hormones. These compounds could help prevent both breast and prostate cancer by blocking and suppressing cancerous changes. There are a number of isoflavones in soy products, but research has shown that genistein is the most potent inhibitor of the growth and spread of cancerous cells. It appears to lower breast-cancer risk by inhibiting the growth of epithelial cells and new blood vessels that tumors require to flourish and is being scrutinized as a potential anti-cancer drug. However, there are some precautions to consider when adding soy to the diet. Eating up to 4 or 5 ounces of tofu or other soy a day is probably fine, but research is being done to see if loading up on soy could cause hormone imbalances that stimulate cancer growth. As a precaution, women who have breast cancer or are at high risk should talk to their doctors before taking pure isoflavone powder and pills, extracted from soy.
Sweet potatoes: They contain many anticancer properties, including beta-carotene, which may protect DNA in the cell nucleus from cancer-causing chemicals outside the nuclear membrane.
Teas: Green tea and Black tea contain certain antioxidants known as polyphenols (catechins) which appear to prevent cancer cells from dividing. Green tea is best, followed by our more common black tea (herbal teas do not show this benefit). According to a report in the July 2001 issue of the Journal of Cellular Biochemistry, these polyphenols that are abundant in green tea, red wine and olive oil, may protect against various types of cancer. Dry green tea leaves, which are about 40% polyphenols by weight, may also reduce the risk of cancer of the stomach, lung, colon, rectum, liver and pancreas, study findings have suggested.
Tomatoes: Tomatoes contain lycopene, an antiox-idant that attacks roaming oxygen molecules, known as free radicals, which are suspected of triggering cancer. Lycopene appears to be more easily absorbed if the tomatoes are eaten in processed form—eitherastomato sauce, paste, or juice. It appears that the hotter the weather, the more lycopene tomatoes produce. Lycopene, has been shown to be especially potent in combating prostate cancer and may also protect against breast, lung, stomach, and pancreatic cancer. Scientists in Israel have shown that lycopene can kill mouth cancer cells. An increased intake of lycopene has already been linked to a reduced risk of breast, prostate, pancreas and colorectal cancer. Recent studies indicate that for proper absorption, the body also needs some oil along with lycopene. Tomatoes also have vitamin C, an anti-oxidant that can prevent cellular damage that leads to cancer. Watermelons, carrots, and red peppers also contain these substances, but in lesser quantities. It is concentrated by cooking tomatoes.
Tumeric: A member of the ginger family, that is claimed to have medicinal properties. Tumeric appears to inhibit the production of the inflammation-related enzyme cyclo-oxygenase 2 (COX-2), which reaches abnormally high levels in certain inflammatory diseases and cancers, especially bowel and colon cancer. A pharmaceutical company Phytopharm in the UK hopes to introduce a natural product, P54, that contains certain volatile oils, which greatly increase the potency of the turmeric spice.
Whole Grains: Whole grains contain a variety of anti-cancer compounds, including fiber, antioxidants, and phytoestrogens. When eaten as part of a balanced diet, whole grains can help decrease the risk of developing most types of cancer.
A considerable amount of information and knowledge has been accumulated regarding the cancer fighting foods. No single food or food substance alone can protect an individual against cancer, but the right combination of plant-based foods in the diet can greatly increase the chances of avoiding cancer. Evidence is mounting that the minerals, vitamins, antioxidants and phytochemicals in many plant foods interact to provide extra cancer protection by working synergisti-cally in the body. For this reason, many nutrition scientists recommend that at least 2/3 of the diet should consist of vegetables, fruit, whole grains and beans.
In some cases, high intakes of individual vitamins can be harmful. An example of this is the risk of high levels of beta-carotene increasing the risk of lung cancer in smokers.
Children can greatly benefit from a diet rich in cancer-fighting foods. The healthy diet will promote a lifetime of good health as well as encourage proper growth. However, vitamin supplementation is not recommended outside of a physician’s or registered dietetian’s care as children have different vitamin requirements and the level of doses appropriate for an adult may not be the same for a child.