- Posted by jdavis on June 22, 2011
A Global Perspective on Diet & Cancer
The new report from the American Institute for Cancer Research’s Diet & Cancer Project, Food, Nutrition and the Prevention of Cancer: a global perspective offers strong new insights into diet and cancer:
- one of the most comprehensive reviews of scientific research in diet and cancer ever done
- the first analysis of food and cancer prevention from a global perspective
- the first report to focus on foods and whole diets, not just compounds within foods
- new dietary guidelines and public policy recommendations for cancer prevention
But as important as all those things, and the many more contained within this report, are, most important of all is the basic message this report provides: Cancer is a preventable disease. Although we still do not know how to prevent all cancers, a major finding of this report is that we now know more than enough to dramatically reduce the too high cancer incidence rates we currently have, and to curb growing cancer rates around the world.
This report provides a foundation now for action based on science, action that could lead to significant reductions in the number of cancer cases which occur each year. As research continues to search for answers in cancer diagnosis and treatment, this report provides consumers and policy makers with direction on what can be done now to reduce cancer risk.
The following is the “Advice to Individuals” presented in the report, Food, Nutrition and the Prevention of Cancer: A Global Perspective. Based on an analysis of more than 4,500 research studies, these guidelines present the best currently available advice on actions to take for lower cancer risk.
1: Choose predominantly plant-based diets rich in a variety of vegetables and fruits, pulses (legumes) and minimally processed starchy staple foods.
2: Avoid being underweight or overweight and limit weight gain during adulthood to less than 5kg (11 pounds).
3: If occupational activity is low or moderate, take an hour’s brisk walk or similar exercise daily, and also exercise vigorously for a total of at least one hour in a week.
4: Eat 400-800 grams (15-30 ounces) or five or more portions (servings) a day of a variety of vegetables and fruits, all year round.
5: Eat 600-800 grams (20-30 ounces) or more than seven portions (servings) a day of a variety of cereals (grains), pulses (legumes), roots, tubers and plantains. Prefer minimally processed foods. Limit consumption of refined sugar.
6: Alcohol consumption is not recommended. If consumed, limit alcoholic drinks to less than two drinks a day for men and one for women.
7: If eaten at all, limit intake of red meat to less than 80 grams (3 ounces) daily. It is preferable to choose fish, poultry and meat from non-domesticated animals in place of red meat.
8: Limit consumption of fatty foods, particularly those of animal origin. Choose modest amounts of appropriate vegetable oils.
9: Limit consumption of salted foods and use of cooking and table salt. Use herbs and spices to season foods.
10: Do no eat food which, as a result of prolonged storage at ambient temperatures, is liable to contamination with mycotoxins.
11: Use refrigeration and other appropriate methods to preserve perishable foods as purchased and at home.
12: When levels of additives, contaminants and other residues are properly regulated, their presence in food and drink is not known to be harmful. However, unregulated or improper use can be a health hazard, and this applies particularly in economically developing countries
13: Do not eat charred food. For meat and fish eaters, avoid burning of meat juices. Consume the following only occasionally: meat and fish grilled (broiled) in direct flame; cured and smoked meats.
14: For those who follow the recommendations presented here, dietary supplements are probably unnecessary, and possibly unhelpful, for reducing cancer risk.
Tobacco: Do not smoke or chew tobacco.
The Reality of Prevention
Our dietary choices play a central role in helping protect us against cancer. That conclusion, drawn from the review and analysis of more than 4,500 research projects, is the foundation of the American Institute for Cancer Research’s Diet & Cancer Project and the key message from the report produced by the project, Food, Nutrition and the Prevention of Cancer: A Global Perspective.
The National Academy of Sciences landmark 1982 report on diet and cancer was the first to make clear the link between diet and cancer. Now, the new Diet & Cancer Project report clearly establishes that the foods we choose play an overwhelming role in fighting cancer.
This report, the first to be an international review of diet and cancer, is the most comprehensive report ever in the field of diet and cancer. The scientific analysis, dietary guidelines, and policy recommendations it provides will help set new directions in research, cancer education and public health policy for years to come, both in the U.S. and around the world.
The Potential of Prevention
- Eating right, plus staying physically active and maintaining a health weight, can cut cancer risk by 30% to 40%.
- Recommended dietary choices coupled with not smoking have the potential to reduce cancer risk by 60% to 70%.
- As many as 375,000 cases of cancer, at current cancer rates, could be prevented each year in this nation through healthy dietary choices.
- A simple change, such as eating the recommended five servings of fruits and vegetables each day, could by itself reduce cancer rates more than 20%.
Cancer Prevention, Diet and Nutrition
30 to 40% of cancers are directly linked to dietary choices according to a 1997 report underwritten by the American Institute for Cancer Research, titled Food, Nutrition, and the Prevention of Cancer: A Global Perspective.
New research is strengthening the link between healthy eating and the prevention of certain types of cancer. Additionally, some diets, notably high calorie and high fat diets, can increase the risk of cancer. A diet full of fresh fruits, vegetables and whole grains yields numerous immediate and short term benefits, and now it is becoming clear how significant the long term benefits are as well. Read on to find out how eating a well-rounded, healthy diet will reduce your risk of many types of cancer and what foods help prevent cancer.
Can certain foods prevent cancer?
Substantial information exists about the links between certain types of cancers and nutrition. It is important to note that other lifestyle factors, such as smoking, alcohol use, exercise level and obesity also play a role in the risk of developing cancer. The list below details common cancers and dietary choices which aid in prevention or increase the risk of the disease. Information provided by the article Cancer and Food on the Victorian (Australian) Government website.
- Lung cancer – this is the leading cause of death from cancer in the world and smoking is mostly responsible. There is convincing evidence that diets high in vegetables and fruits are protective against lung cancer and that compounds called carotenoids, which are present in significant amounts in these foods, are probably responsible for some of this effect. However, the use of antioxidant supplements, such as beta-carotene and vitamin E, has not been proven to be effective in either prevention or treatment of lung cancer and may, in fact, increase the risk of developing cancer in those who smoke.
- Breast cancer – this is the most common type of cancer in women in the world. There is an increased risk of breast cancer with factors including rapid early growth, greater adult height and weight gain in adulthood. Much of the risk of developing breast cancer involves factors that influence oestrogen levels during a woman’s reproductive life, such as age of menarche (first period), number of pregnancies and breastfeeding practices. Obese post-menopausal women have more than twice the average risk of breast cancer. Diets high in mono-unsaturated fat and high in vegetables and fruits may reduce the risk, while alcohol consumption increases the risk.
- Prostate cancer – this is the third most common cause of death of men in Australia. Vegetables – soy in particular – may decrease the risk, while a high fat diet that comprises mostly animal fat sources (such as dairy products, fatty meats and takeaway foods) may increase the risk. Lycopene – a potent antioxidant found in tomatoes, tomato-based products, watermelon and strawberries – may help lower the risk.
- Bowel cancer – this is the fourth most common cancer in the world. Up to 70 percent of cases can be prevented by following a healthy lifestyle. Physical activity and a diet high in vegetables and fiber are protective, while a high red meat intake (especially processed meat) and alcohol may increase the risk.
Tips for avoiding carcinogens and reducing the risk of cancer
Carcinogens are cancer causing substances found in food. Take the following precautions when making your food choices:
- Avoid foods that look or smell moldy, as they likely contain aflatoxin, a potent liver carcinogen. Aflatoxin is most commonly found on peanuts.
- Do not cook oils on high heat. Low-heat cooking or baking (less than 240 degrees) prevents oils or fats from turning carcinogenic. When possible, replace heating and frying with boiling or steaming.
- Beware of cured, dried, and preserved meats. Nitrates and nitrites are compounds used to cure meat, and are metabolized into a substances called nitrosamine during the curing process. Nitrosamines are found in cooked bacon and sausage, cured pork, and dried beef. They are known to be a potent carcinogen. Nitrosamines are also formed during the drying process when beer is manufactured. The highest levels are found in dark beers.
- Go easy on the barbecue. Burning or charring meats creates substances called heterocyclic amines (HCAs), which are released when high heat is applied to a compound called creatine, found in animal blood and tissue. HCAs are most often associated with cancers of the gastrointestinal tract, though some laboratory studies have suggested a connection to lung and breast tumors. One study of more than 40,000 women found that those who consistently ate well-done meat were nearly five times more likely to develop breast cancer than those who ate their meat rare or medium-cooked. One way to reduce HCAs before barbecuing is to pre-heat the meat in the microwave, which dries up some of the juices and the creatine. This does not, however, eliminate the HCAs altogether.
- Steer clear of smoked foods. Carcinogenic substances called polycyclic aromatic hydrocarbons (PAHs) form on the surface of food during the smoking process.
- Buy organic if possible. Additives and pesticides found in commercially grown produce and processed foods are also suspected carcinogens. It is best to buy organic fruits and vegetables whenever possible. The Physicians’ Desk Reference (PDR) website offers a few simple steps you can take to protect yourself from food contaminants:
- Use waxed paper rather than plastic wrap when microwaving.
- Wash or peel all fruits and vegetables. Use a vegetable brush for washing. Washing does not eliminate all pesticide residue, but it will reduce it.
- Buy local produce whenever possible. It is less likely to have been treated with chemicals to prevent spoilage than fruits and vegetables that travel a long distance to the market.
Food guidelines for cancer prevention
Taking the above points into consideration, a healthy diet for cancer prevention emphasizes the following foods:
- Eat at least five servings of fruits and vegetables each day (more are recommended: see What is the ‘5 A Day’ program and how can it help prevent cancer?). A recent report sponsored by the World Cancer Research Fund and the American Institute for Cancer Study estimated that eating 400 or more grams daily of fruits and vegetables could prevent at least 20 percent or more of all cancers. In addition, those who eat the highest amount of fruits and vegetables have been shown to have one half the cancer risk as those eating the least amounts. Plant-derived foods contain phytochemicals, nutrients that act powerfully to prevent a healthy cell from turning cancerous. Phytochemicals have been studied for their role in boosting detoxification of the cells and stimulating the immune system, as well as their anti-bacterial and anti-viral properties—all hugely helpful in maintaining a healthful inner environment that reduces the likelihood of cancer from forming. Fruits and vegetables are high in vitamin A and beta carotene, the B Vitamins, Vitamin C, and essential minerals.
- Choose foods from other plant sources, such as breads, cereals, grain products, rice, or beans several times each day. Limit consumption of refined carbohydrates, including pastries, sweetened cereals, soft drinks, and sugars. Choose whole foods that are rich in complex carbohydrates, vitamins, and minerals over minimally-processed or highly-processed foods.
- Eat plenty of fiber. Fiber moves cancer-causing compounds out of the body before they can create harm. It is also thought to dilute potential carcinogens, and may effect hormone production, thus lowering the incidence of hormone-related cancers like breast and prostate cancers. The National Cancer Institute recommends 20-30 grams of fiber per day. Foods rich in fiber are:
- Whole grains such as barley and oats, oat bran, and nuts
- Apples, bananas, blackberries, citrus fruits, pears, and prunes
- Lima , kidney, pinto, and navy beans, chick peas, black-eyed peas, and especially lentils
- Brussel sprouts, carrots, tomatoes, potatoes, and broccoli
- To help you increase the fiber in the diet, the Cancer Research and Prevention Foundation suggests that you substitute:
- brown rice for white
- whole wheat bread or rye for white
- black beans for ground meat
- bran muffin for croissant or pastry
- popcorn for potato chips
- unpeeled apple for applesauce
- baked potato with skin for mashed potato
- bean dip or salsa for sour cream dip
- Partake of healthy fats. Healthy fats are good for you, in moderation. Olive oil, for instance, has been shown to reduce the risk of breast cancer. The human body needs fat for normal cellular functioning. So when you eat fat, replace saturated fats with unsaturated fats. These include sunflower, corn, and soybean oils (polyunsaturated fats) and canola and olive oils (monounsaturated fats). Two of the most beneficial fats are omega-6 and omega-3 oils, known as essential fatty acids (EFAs). The body cannot manufacture these fats, so they must be provided through the diet. Omega-6 fat is found in abundance in vegetable oils, margarines, mayonnaise, and salad dressings; omega-3 fat in fish, fish oil, and green plant food sources, especially spinach and mustard greens. Omega-3 fatty acids from fish oil have been shown to have an anti-carcinogenic effect in the laboratory. Strengthen your immune system.
The Wellness Community website put together some eating suggestions for maximum immunity. The following chart lists some of the most potent nutrients in the fight against cancer, along with their food sources:
|Most Potent Nutrients in the Fight Against Cancer|
|Vitamin A||Fish liver oils, liver|
|Beta Carotene(provitamin A)||Orange, yellow and dark green leafy vegetables including carrots, cantaloupe, apricots, spinach|
|Vitamin B2 (Riboflavin)||Whole and enriched cereals and breads. Lean meat, milk, eggs, liver, dried yeast|
|Vitamin B6 (Pyridoxine)||As for B2, and bananas|
|Folic Acid||Leafy green vegetables, meats|
|Pantothenic Acid||Brewer’s yeast, legumes, salmon, whole grains|
|Vitamin C||Citrus fruits, berries, broccoli, bell peppers|
|Vitamin E||Leafy green vegetables, egg yolk, liver, wheat germ|
|Selenium||Garlic, legumes, fish, asparagus|
|Iron||Liver, peas, egg yolk, asparagus|
|Zinc||Liver, oysters, soybeans, sunflower seeds|
|Magnesium||Green leafy vegetables, nuts, seafood|
|Manganese||Bananas, bran, pineapple, nuts|
|Protein||Lean meat, poultry, fish, shellfish, eggs, legumes, broccoli, sunflower seeds|
|Antioxidants||Citrus fruits, legumes, whole grains|
|Phytonutrient||All plant sources of food, especially dark and brightly colored fruits and vegetables|
African Americans are at a higher risk for cancer and other diseases as compared to whites, and are also more likely to die from cancer. At the same time, African Americans consume the least amount of fruits and vegetables of any ethnic group. To help address the disparity in consumption rates, the 5 A Day initiative developed a wellness program for African American churches called Body and Soul. For the past ten years, this program has helped support healthy living, including increased fruit and vegetable consumption. Visit the 5 A Day website for more information or to start a Body and Soul program at your own church.
A final word about variety: Pay attention to the colors of the fruits and vegetables you choose—green, red, yellow, orange, purple, blue, and white—as nature has imbued each with unique nutrients and phytochemicals that deliver a more complete nutritional benefit when consumed together. Think of assembling a rainbow of colors on your plate; it’s more pleasing to the eye and will give you a good balance of phytonutrients at each meal.
Specific foods that have the most powerful preventative effect
Certain foods have come to the forefront in the past few decades of cancer research as heavyweights in the battle against cancer. The National Institute for Cancer Research presents an all-star line up of foods known for their effective cancer-fighting properties:
- Beans (or legumes), which include lentils and peas, are rich in fiber and contain several chemicals that boost immunity to cancer. Saponins have shown the ability to inhibit the growth of cancer cells in different tissues; protease inhibitors slow down cancer cells from multiplying and suppress proteases, potent cell destroyers; and phytic acid slows the growth of tumors. A study of 3,237 men of different ethnic backgrounds showed that the risk for prostate cancer was 38 percent lower in those who ate the most amount of beans, as compared to those who ate the least amount.
- Berries are good sources of vitamin C and fiber, as well as a wonderful substance called ellagic acid, which has been found in laboratory studies to prevent cancers of the skin, bladder, lung, esophagus and breast. Strawberries and raspberries are particularly high in ellagic acid, and blueberries are loaded with a class of anti-oxidants as powerful as any seen. So splurge on berries in your morning cereal.
- Cruciferous vegetables include broccoli, cauliflower, Brussel sprouts, cabbage, kale, Swiss chard, and bok choy. Substances in these vegetables have shown the ability to stop the growth of cancer cells in laboratory studies, particularly by regulating a complex system of enzymes that provide a good line of cancer defense. High consumption of cruciferous vegetables has been associated with a decreased risk for lung, stomach and colorectal cancers.
- Dark green leafy vegetables like spinach, romaine lettuce, leaf lettuces, kale, mustard greens, collard greens, and Swiss chard all contain high amounts of fiber, folate and a wide range of anti-oxidants which attack and remove hazardous free radicals from the body. Researchers have found that carotenoids in dark green leafy vegetables are effective in inhibiting the formation of breast and skin cancer tumors, and preventing lung and stomach cancer. High folate levels in men who ate diets rich in green leafy vegetables have been correlated with a reduced risk of lung cancer, particularly among men who smoke. Results from the Iowa Women’s Health Study showed a 44%lower risk rate for breast cancer in women who ate the most green leafy vegetables, as compared to those who ate the least.
- Flaxseed is the best known dietary source for a substance called lignans, which appear to replicate the action of estrogen in the body. Flax oil does not contain lignans, though they are often added by the manufacturers. In some short-term human studies, flaxseed consumption modified estrogen metabolism such that there appeared to be a possible protective effect against breast cancer. It has also been shown to inhibit the formation of colon, breast, skin and lung tumors in more than one laboratory study. Flaxseed is also high in omega-3 fats essential fatty acids.
- Garlic is a natural antibiotic and immune system enhancer, a free radical attacker, and it increases the enzymes that break down carcinogens in the body. Ample research has shown garlic to be one of the best foods to eat for cancer prevention, linking its consumption with slowing or stopping the growth of tumors in prostate, bladder, and stomach tissue, and preventing cancers of the skin and lung. The evidence is particularly compelling for garlic as a preventative agent against prostate and stomach cancers. The Iowa Women’s Health Study found that women who regularly ate garlic had a lower risk for colon cancer. Eat as much of this mighty food as you can stand!
- Grapes, especially red and purple varieties, contain high levels of resveratrol, which belongs to a classification of plant chemicals called polyphenols. Resveratrol has been shown to slow the growth of cancer cells and inhibit the formation of tumors in lymph, liver, stomach and breast cells.
- Green tea is the best source of catechins in the human diet, containing about three times as many catechins as there are in black tea. The catechins found in tea selectively inhibit specific enzyme activities that lead to cancer and may also repair cellular damage caused by free radicals. Green tea has been shown to inhibit or block cancer development in colon, liver, breast, and prostate cells. Studies done in Asia show that frequent use of green tea lowers the risk for bladder, colon, stomach, pancreatic, and esophageal cancers. It has also been shown to aid in preventing recurrence of stage 1 breast cancer.
- Soy foods, which include tofu, soymilk, soybeans, soynuts, miso (soy paste), tempeh, and soy burgers, are particularly relevant in their effects on hormone-related cancer. Soy contains phytoestrogens, a plant-derived, weaker form of estrogen that some scientists believe replaces the body’s stronger form of estrogen at estrogen receptor sites in the breast, thereby reducing the probability of developing cancer. Several human and laboratory studies have suggested that soy consumption early in life may help protect against breast cancer later in life. However, according to breastcancer.org, many doctors worry that phytoestrogens in soy may increase the risk of women who have already had breast cancer. In another human study, men who said they drank soymilk more than once per day for 20 years were found to have 70% lower prostate cancer risk than men who never drank soymilk.
- Tomatoes contain the phytochemical lycopene, which is also found to a lesser extent in watermelon, papaya, and pink grapefruit. More than 35 studies have confirmed a lower risk of cancer as a result of high lycopene and tomato intake, especially cancers of the prostate, stomach, and lung. Lycopene compounds tend to concentrate in tissues of the prostate, so its protective agency there has received the most attention. Tomatoes have the highest anti-cancer potential when taken in a processed form such as tomato sauce, tomato paste, and tomato juice, because of easier absorption. The PDR website reported a study that found that people with the lowest levels of lycopene are three times more likely to get lung cancer than those with the highest levels. African Americans in the same study were found to have eight times the risk of developing cancer when lycopene levels were lowest.
- Turmeric is the spice most often used in curry powder. It has an active ingredient called curcumin that has shown resistance to colon, breast, liver, oral, skin, and stomach tumors in laboratory testing on animals.
- Yogurt consumed in high quantities has been linked in some population studies to reduced risks of cancer, particularly of the breast and colon.