Because carcinogenesis occurs over years, most data linking diet and cancer is epidemiological (case control, cohort, or cross-sectional studies) It is estimated that one third of the cancer deaths each year in the US can be attributed to nutrition and other lifestyle factors (not including smoking)
Types of Epidemiologic Studies of Cancer Case Control Studies The diets of individuals with cancer are compared with those of cancer-free controls matched for age, sex, and other key factors. Cohort Studies The diets of different groups of subjects are determined before cancer onset, and the incidences of developing cancers in each group are compared. Cross-sectional Studies The diets of different groups of subjects are compared, using the same measures at a single point in time.
Nutrition in the Etiology of Cancer– contd Complex relationship Dietary carcinogens: naturally occurring and added in food preparation and preservation Inhibitors of carcinogenesis: antioxidants, phytochemicals Enhancers of carcinogenesis Latency period between initiation and promotion
Energy Intake, Body Weight, Obesity, and Physical Activity Energy restriction inhibits cancer and extends life span in animals Positive associations between overweight and cancers of the breast, endometrium, kidney, colon, prostate, and others Overweight increases risk of cancer recurrence and decreases survival Physical activity is inversely associated with cancer
Nutrition and Cancer Etiology Fat Protein Soy and phytoestrogens Carbohydrates: fiber, sugars, and glycemic index Fruits and vegetables Nonnutritive sweeteners
Nutrition and Cancer Etiology– contd Alcohol Coffee and tea Methods of food preparation and preservation Cancer chemoprevention Cancer prevention recommendations: nutrition and physical activity Nutrition and physical activity recommendations for cancer survivors
Color Code System of Vegetables and Fruits ColorPhytochemicalVegetables and Fruits RedLycopeneTomatoes and tomato products, pink grapefruit, watermelon Red/purpleAnthocyanins, polyphenols Berries, grapes, red wine, prunes Orangeα-, β-caroteneCarrots, mangoes, pumpkin Orange/yellowβ-cryptoxanthin, flavonoids Cantaloupe, peaches, oranges, papaya, nectarines Yellow/greenLutein, zeaxanthinSpinach, avocado, honeydew, collard and turnip greens GreenSulforaphanes, indolesCabbage, broccoli, Brussels sprouts, cauliflower White/greenAllyl sulphidesLeeks, onion, garlic, chives Data from Heber D: Vegetables, fruits and phytoestrogens in the prevention of diseases, F Postgrad Med 50:145, 2004.
Guidelines for Cancer Prevention 1.Choose a diet rich in a variety of plant-based foods. 2.Eat plenty of vegetables and fruits. 3.Maintain a healthy weight and be physically active. 4.Drink alcohol only in moderation, if at all. 5.Select foods low in fat and salt. 6.Prepare and store food safely. And always remember... Do not use tobacco in any form. From American Institute for Cancer Research: Simple steps to prevent cancer, Washington, DC, 2000, AICR.
Nutrition in Cancer Prevention Diets contain both inhibitors and enhancers of carcinogenesis Animal studies also test the effect of food and nutrition on cancer and provide guidance for epidemiological studies
Fat High intake of total and saturated fat is associated with increased risk of breast, colon, lung and prostate cancers High fat diets are associated with obesity, which is linked with cancer of the colon, rectum, esophagus, gall bladder, breast, endometrium, pancreas, and kidney Animal fat (from meat and dairy) was associated with increased risk of breast cancer in the Nurses Health study and others Higher omega-3 vs omega 6 may reduce risk of breast cancer Low fat diet (<20% fat) may reduce risk of recurrence of breast cancer
Energy Intake and Physical Activity Total energy intake is strongly associated with breast cancer in postmenopausal women Physical activity may have a protective effect Women who spent an average 3.8 hours per week in physical activities had lower risk of colon, reproductive cancers
Obesity is a Risk Factor for: Breast cancer (among postmenopausal women) Colon Endometrium Esophagus Gallbladder Pancreas Kidney Is also a risk factor for cancer recurrence
Protein Difficult to isolate effects of protein, since protein diets are in fat and in fiber Low protein diets seem to reduce the risk of cancer, while risk is increased by very high protein intakes Increased meat intake is associated with increased risk of colon cancer and advanced prostate cancer
Fiber Observational studies and case control studies indicate that fiber-rich diets are associated with a protective effect in colon cancer Higher intakes of vegetables were inversely associated with colon cancer risk in one study But high fiber diets also tend to be lower in meat, fat, and refined carbohydrates
Fiber Two intervention trials evaluating the effect of fiber on polyp and adenoma recurrence failed to show an effect of high fiber vs low fiber diets Recommendation is to eat high fiber foods despite lack of conclusive evidence re cancer
Carbohydrate and Glycemic Index High glycemic-index diet associated with increased risk of cancers including ovarian, endometrial, breast, colorectal, pancreas, and lung Limit processed foods and refined sugars and emphasize whole grains and low GI foods
Fruits and Vegetables Fruits and vegetables found to be associated with lower risk in 128 of 156 dietary studies Increased consumption of fruits and vegetables is associated with lower risk of cancers of the oral cavity, esophagus, stomach, colon, rectum, and bladder Evidence less strong for hormone-related cancers such as breast and prostate cancer
Fruits and Vegetables People who develop cancer tend to have low intakes of Raw and fresh vegetables Leafy green vegetables Lettuce, carrots, raw and fresh fruit Cruciferous (cabbage family) vegetables Flavenoids and lignans (soy, grains, vegetables) are associated with lower risk of sex hormone- related cancers
Fruits and Vegetables Low in energy, good sources of fiber, vitamins, minerals Good sources of antioxidants (vitamins C, E, selenium, phytochemicals such as carotenoids, flavonoids, plant sterols, allium compounds, indoles, phenols, terpenes Do not yet know what is the protective agent(s) so best to use food sources
Plant based foods may prevent cancer by Inhibiting hormone-dependent steps in tumor formation and protecting genetic material from carcinogenic agents Suppressing free radical production Serving as bulking agents to dilute carcinogens and decrease gastrointestinal transit time Stimulators of physiologically active and anti-cancer enzymes Mobley C. Nutrition and cancer prevention. In McCallum and Polisena, The Clinical Guide to Oncology Nutrition. Oncology Nutrition Dietetic Practice Group, 2000.
Cancer Chemoprevention Studies ß-carotene supplementation in Finnish smokers was associated with a 16% higher incidence of lung cancer Heavy alcohol intake seemed to enhance negative effects However, diet studies suggest that high fruit and vegetable consumption, particularly carotenoids, tomatoes, and tomato-based products may reduce risk of lung cancer
Supplementation in Persons at High Risk for Esophageal-Gastric Cancer in China Study in area of China with diet low in micronutrients and very high risk of esophageal and gastric cancer ß-carotene, vitamin E, and selenium at 5X the RDA was associated with significantly lower mortality from all cancers
Calcium and Cancer Risk Several studies suggest that foods high in calcium may reduce the risk for colorectal cancer and that calcium supplements may reduce the formation of colorectal polyps However, there is evidence that high calcium intake, especially supplements, is associated with increased risk of prostate cancer Bottom line: get calcium through food sources
Lycopene and Cancer Risk Lycopene is a red-orange carotenoid found in tomatoes and tomato-based foods Several studies show that consuming tomato products reduces the risk of some cancers, but unclear whether lycopene is responsible Absorption of lycopene is enhanced when lycopene-containing vegetables are cooked and eaten with fat No evidence that supplements are safe and effective in cancer prevention. Source: American Cancer Society, accessed 2005
Preserved Meats and Cancer Risk Some studies link eating large amounts of preserved meat to increased risk of colorectal and stomach cancers May or may not be due to nitrites Nitrites can be converted in the stomach to carcinogenic nitrosamines, which may increase the risk of stomach cancer Vegetables and fruit retard the conversion of nitrites to nitrosamines
Cooked Meat and Cancer Risk Frying, broiling, and grilling meats at high temperatures creates chemicals that might increase cancer risk (cause cancer in animals) Use techniques such as braising, steaming, poaching, stewing and microwaving
Soy and Cancer Risk Soy contains several phytochemicals (phytoestrogens) which have weak estrogen activity and appear to protect against hormone- dependent cancers in animal studies No evidence shows soy supplements reduce cancer risk High doses of soy may increase the risk of estrogen-responsive cancers, such as breast or endometrial cancers in certain women Breast cancer survivors should consume only moderate amounts
Alcohol Alcohol associated with carcinogenesis in cancers of the mouth, pharynx, larynx, esophagus, lung, colon, rectum, liver and breast (USDHHS, 2000) Appears to act synergistically with tobacco Malnutrition associated with alcoholism may also be implicated
Coffee and Tea Coffee has been investigated as a possible risk factor for a variety of cancers, but does not appear to be associated with increased cancer Regular drinking of green tea and other sources of polyphenols may reduce the risk of stomach cancer Consumption of very hot drinks may increase the risk of esophageal cancer
Artificial Sweeteners Cyclamate banned as food additive in US in 1969 and saccharine in 1977 after being associated with bladder cancer in mice Under public pressure, saccharine returned to the market; it was reviewed and taken off the list of potential carcinogens in 2000 Aspartame: no evidence implicating it in increased cancer risk
Artifical Sweeteners Five artificial sweeteners on the market: Acesulfame-K Aspartame Neotame Saccharine Sucralose
Hyperinsulinemia and Cancer Increased body mass index may promote hyperinsulinemia and metabolic syndrome Insulin resistance/hyperinsulinemia, higher estrogen levels, and insulin-like growth factor I may act synergistically to promote tumor growth, particularly mammary tumors.
Food Safety and Cancer Naturally occurring carcinogens (aflatoxins in peanuts, safrol in plant oils, tannins in grains and grapes, benzopyrene formed by smoking meat and fish) Naturally found in plant foods like celery, parsley, figs, mustard, pepper, citrus oils Pesticides
Food Safety and Cancer Choose in-season, locally grown produce Rinse fruits and vegetables and remove outer leaves before eating Use proper food storage to prevent growth of fungal carcinogens Marinate protein foods to decrease cooking time Use cooking methods to avoid contact of foods and food drippings with flames Use lower cooking temperatures with protein foods Mobley C. Nutrition and cancer prevention. In McCallum and Polisena, The Clinical Guide to Oncology Nutrition. Oncology Nutrition Dietetic Practice Group, 2000
AICR Diet and Health Guidelines for Cancer Prevention Choose a diet rich in a variety of plant- based foods Eat plenty of vegetables and fruits. Maintain a healthy weight and be physically active. Drink alcohol only in moderation, if at all. Select foods low in fat and salt. Prepare and store food safely.
American Cancer Society Guide to Nutrition and Activity Eat a variety of healthful foods, with an emphasis on plant sources. Eat five or more servings of a variety of vegetables and fruits each day. Include vegetables and fruits at every meal and for snacks. Eat a variety of vegetables and fruits. Limit French fries, snack chips, and other fried vegetable products. Choose 100% juice if you drink fruit or vegetable juices.
American Cancer Society Guide to Nutrition and Activity Choose whole grains in preference to processed (refined) grains and sugars. Choose whole grain rice, bread, pasta, and cereals. Limit consumption of refined carbohydrates, including pastries, sweetened cereals, soft drinks, and sugars.
American Cancer Society Guide to Nutrition and Activity Limit consumption of red meats, especially those high in fat and processed. Choose fish, poultry, or beans as an alternative to beef, pork, and lamb. When you eat meat, select lean cuts and smaller portions. Prepare meat by baking, broiling, or poaching, rather than by frying or charbroiling.
American Cancer Society Guide to Nutrition and Activity Choose foods that help maintain a healthful weight. When you eat away from home, choose food low in fat, calories, and sugar and avoid large portions. Eat smaller portions of high-calorie foods. Be aware that low fat or fat free does not mean low calorie and that low-fat cakes, cookies, and similar foods are often high in calories. Substitute vegetables, fruits, and other low-calorie foods for calorie-dense foods such as French fries, cheeseburgers, pizza, ice cream, doughnuts, and other sweets.
Lifestyle Changes to Reduce Breast Cancer Risk Reducing alcohol consumption Breastfeeding Avoiding obesity Being physically active Source: American Cancer Society, accessed 2005
Lifestyle Change to Prevent Colon Cancer Increase your physical activity Eat more vegetables and fruit Limit intake of red meats Avoid obesity Avoid excess alcohol Source: American Cancer Society, accessed 2005
Lifestyle Changes to Prevent Oral and Esophageal Cancers The best advice to reduce the risk of oral and esophageal cancers is to: Avoid all forms of tobacco Restrict alcohol consumption Avoid obesity
Lifestyle Changes to Prevent Pancreatic Cancer Avoid tobacco use Maintain a healthful weight Remain physically active Eat five or more servings of vegetables and fruits each day Source: American Cancer Society, accessed 2005
Lifestyle Changes to Prevent Prostate Cancer Limit intake of animal products, especially red meat and high-fat dairy products Eat five or more servings of vegetables and fruits each day
Lifestyle Changes to Prevent Stomach Cancer Eat at least five servings of vegetables and fruits daily. Stomach cancer rates are falling due to reduced infection with h. pylori
At Present, There Are No Nutritional Risk Factors for Brain Cancer Leukemias Ovarian cancer Source: American Cancer Society, accessed 2005
Diet Recommendations for Cancer Survivors Cancer survivor may harbor undetected primary or disseminated cancer cells A cured cancer pt is at increased risk for other primary cancers in the same organ or other organs General dietary guidelines are also appropriate for recovering cancer pts Dietary regimens should a) avoid stimulating growth and spread of remaining tumor cells and b) provide maximum prevention against new primary tumors Nixon DW. Nutrition during cancer recovery. In McCallum and Polisena, The Clinical Guide to Oncology Nutrition. Chicago, The American Dietetic Association, 2000.
Recommendations for Cancer Survivors Limit total fat intake to 15-20% of total calories. Monounsaturated fats are preferred. Aim for 10-12 daily servings of a variety of whole vegetables and fruits. Consume 4-6 servings of whole grains daily. Breast cancer pts should eliminate or severely restrict alcohol intake
Dietary Recommendations for Cancer Survivors Consider a Vitamin E supplement of 200 IU/day to replace deficit from reduced fat intake Standard dose multivit daily (not to exceed 100% RDA). This does not replace cancer- fighting foods Exercise moderately (30 minute daily walk, for example) Maintain desirable body weight