Reducing the Risk of Cancer with Healthy Food Choices and Physical Activity
When I copied this 2001 set of guidelines into a Word document I found that it is 23.5 pages long, with another 4.5 pages of footnotes & references. I don’t think you want to read all of it, so I decided to summarize it for you by printing selected portions that represent a little less than one quarter of the report.
The Importance of Diet and Physical Activity in Cancer Prevention
For the great majority of Americans who do not smoke cigarettes, dietary choices and physical activity are the most important modifiable determinants of cancer risk. Evidence suggests that one third of the more than 500,000 cancer deaths that occur in the United States each year can be attributed to diet and physical activity habits [emphasis added], with another third due to cigarette smoking. Although genetic inheritance influences the risk of cancer, and cancer arises from genetic mutations in cells, most of the variation in cancer risk across populations and among individuals is due to factors that are not inherited. Behavioral factors such as smoking cigarettes, consuming foods along certain patterns of diet [emphasis added], and staying active across the lifespan can substantially affect one's risk of developing cancer. Because healthful individual behaviors are most effectively enabled by social and environmental support within communities, these 2001 guidelines include, for the first time, an explicit recommendation for community action. . .
Although the randomized, controlled trial is often considered the gold standard for scientific conclusions, such evidence is not presently available—and may never become available—for many dietary factors associated with cancer risk. Inferences about the many complex interrelationships among diet, physical activity, and cancer risk are based, for the most part, on observational studies coupled with advancing understanding of the biology of cancer. In considering the totality of evidence from a variety of sources, these guidelines take into consideration both the benefits to cancer risk reduction and overall health benefits. Although no diet can guarantee full protection against any disease, these guidelines offer the best information currently available about how diet and physical activity can reduce the risk of cancer. The ACS guidelines are consistent with guidelines from the American Heart Association for the prevention of coronary heart disease as well as for general health promotion, as defined by the Department of Health and Human Services' 2000 Dietary Guidelines for Americans. . .
AMERICAN CANCER SOCIETY GUIDELINES FOR NUTRITION AND PHYSICAL ACTIVITY
Social, economic, and cultural factors strongly influence individual choices about diet and physical activity. While most Americans would like to adopt a healthful lifestyle, many encounter substantial barriers that make it difficult to follow diet and activity guidelines. Indeed, current trends toward increasing consumption of high-calorie convenience foods and restaurant meals, and declining levels of physical activity are contributing to an alarming epidemic of obesity among Americans of all ages and across all population segments. Longer workdays and more households with multiple wage earners reduce the amount of time available for preparation of meals, with a resulting shift toward increased consumption of food outside the home—often processed foods, fast foods, and snack foods. Reduced leisure time, increased reliance on automobiles for transportation, and increased availability of electronic entertainment and communications media all contribute to a less active and increasingly sedentary lifestyle. These trends are of particular concern, especially with regard to the adverse effects they have on the long-term health of children, who are establishing lifetime patterns of diet and physical activity, as well as on the poor, who live in communities with less access to safe and healthful lifestyle options. . .
Recommendations for Individual Choices
There is strong scientific evidence that healthful dietary patterns, in combination with regular physical activity, can reduce cancer risk. Approximately 35 percent of cancer deaths in the United States may be avoidable through dietary modification [emphasis added]. The scientific study of nutrition and cancer is highly complex, and many important questions remain unanswered. It is not presently clear how single nutrients, combinations of nutrients, overnutrition and energy imbalance, or the amount and distribution of body fat at particular stages of life affect one's risk of specific cancers. However, epidemiological studies have shown that populations whose diets are high in vegetables and fruits and low in animal fat, meat, and/or calories have a reduced risk of some of the most common types of cancer. Until more is known about the specific components of diet that influence cancer risk, the best advice is to emphasize whole foods and certain broad dietary patterns, as described within these guidelines.
1. 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.
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.
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 have smaller portions.
• Prepare meat by baking, broiling, or poaching rather than by frying or charbroiling.
Choose foods that help you maintain a healthful weight.
• When you eat away from home, choose foods that are low in fat, calories, and sugar, and avoid large portion sizes.
• Eat smaller portions of high-calorie foods. Be aware that "low-fat" or "nonfat" 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.
Beneficial Effects of Vegetables and Fruits
Greater consumption of vegetables, fruits, or both together has been associated in the majority of epidemiological studies with a lower risk of lung, oral, esophageal, stomach, and colon cancer. . .
It is presently unclear which components of vegtetables and fruits are most protective against cancer. Vegetables and fruits are complex foods, each containing more than 100 potentially beneficial vitamins, minerals, fiber, and other substances that may help to prevent cancer.
Vegetables and fruits also contain specific phytochemicals, such as carotenoids, flavonoids, terpenes, sterols, indoles, and phenols that show benefit against certain cancers in experimental studies. There is ongoing research, for example, on the potential benefits of green and dark yellow vegetables, plants related to the cabbage family, soy products, legumes, allium (onion and garlic), and tomato products. Until more is known about specific food components, the best advice is to eat five or more servings of a variety of vegetables and fruits in their various forms: fresh, frozen, canned, dried, and juiced. . .
Whole Grains
Grains such as wheat, rice, oats, and barley, and the foods made from them, constitute the basis of a healthful diet. Whole grains are an important source of many vitamins and minerals that have been associated with lower risk of colon cancer, such as folate, vitamin E, and selenium. Whole grains are higher in fiber, certain vitamins, and minerals than processed (refined) flour products. Although the association between fiber and cancer risk is inconclusive, consumption of high-fiber foods is still recommended. Since the benefits grain foods impart may derive from their other nutrients as well as from fiber, it is best to obtain fiber from whole grains—and vegetables and fruits—rather than from fiber supplements. . .
Dietary Fat and Consumption of Red Meat
High-fat diets have been associated with an increase in the risk of cancers of the colon and rectum, prostate, and endometrium. . . Research continues to examine whether the association between high-fat diets and various cancers in some epidemiological studies is due to the total amount of fat, the particular type of fat (saturated, monounsaturated, or polyun-saturated), the calories contributed by fat, or some other factor associated with high-fat foods. Fats such as the saturated fat in red meats, omega-3 fatty acids in fish oils, or monounsaturated fats in olive oil, for example, likely differ in their effects on cancer risk. . .
Foods from animal sources remain major contributors of total fat, saturated fat, and cholesterol in the American diet. Although meats are good sources of high-quality protein and can supply many important vitamins and minerals, consumption of meat—especially red meats (beef, pork, lamb)—has been associated with cancers in many studies, most notably those of the colon and prostate. How much of this association is due to specific constituents within meat (such as saturated fats) or to correlated dietary factors is presently unclear. . .
Much evidence indicates that saturated fat may be particularly important in increasing risk of cancer as well as for heart disease. The best way to reduce saturated fat intake is to make wise choices in the selection and preparation of animal-based foods. Choose lean meats and lower-fat dairy products, and substitute vegetable oils for butter or lard. Food labels can be a useful guide to choosing packaged foods lower in saturated fat. Choose smaller portions and use meat as a side dish rather than as the focus of a meal. Emphasize beans, grains, and vegetables in meals to help shift dietary patterns to include more foods from plant rather than animal sources.
Preparation methods are also important. Baking and broiling meat, rather than frying, reduces its overall fat content. Meat should be cooked thoroughly to destroy harmful bacteria and parasites, but should not be charred.
Choosing Foods that Help Maintain a Healthful Body Weight
Most people cannot maintain a healthful body weight without limiting caloric intake while maintaining regular physical activity. Current trends indicate that the largest percentage of calories in the American diet comes from foods high in fat, sugar, and refined carbohydrates. Consuming a varied diet that emphasizes plant-based foods may help to displace these calorie-dense foods. Limiting portion sizes, especially of these types of foods, is another important strategy to reduce total caloric intake.
Replacing dietary fat with foods that are high in calories from sugar and other refined carbohydrates does not protect against obesity. The decrease in fat intake and increase in consumption of refined carbohydrates that occurred in the United States between 1977 and 1995 coincided with an 8% increase in the prevalence of obesity. Excessive intake of sugar and other highly-refined carbohydrates may contribute to insulin insensitivity, alterations in the amount and distribution of body fat, and increased concentrations of growth factors that may promote the growth of cancers.
2. Adopt a physically active lifestyle.
• Adults: engage in at least moderate activity for 30 minutes or more on five or more days of the week; 45 minutes or more of moderate-to-vigorous activity on five or more days per week may further enhance reductions in the risk of breast and colon cancer.
• Children and adolescents: engage in at least 60 minutes per day of moderate-to-vigorous physical activity for at least five days per week.
Benefits of Physical Activity
Scientific evidence indicates that physical activity may reduce the risk of several types of cancer, including cancers of the breast and colon, and can provide other important health benefits. Physical activity acts in a variety of ways to impact cancer risk. Regular physical activity helps maintain a healthful body weight by balancing caloric intake with energy expenditure. Other mechanisms by which physical activity may help to prevent certain cancers may involve both direct and indirect effects. . . The benefits of physical activity go far beyond reducing the risk of cancer, however, and include reducing the risk of other chronic diseases, such as heart disease, diabetes, osteoporosis, and hypertension.
Recommended Amount of Activity
There are many unanswered questions about the optimal intensity, duration, and frequency of physical activity needed to reduce cancer risk. However, current evidence suggests that there is substantial risk reduction for colon cancer from simply not being sedentary. And by participating in moderate-to-vigorous physical activity at least 45 minutes on five or more days of the week, individuals may achieve optimal activity levels needed to reduce the risk of developing both breast and colon cancers, as well as several other types of cancer, including kidney, endometrial, and esophageal cancer. Moderate-to-vigorous physical activity is needed to metabolize stored body fat and to modify physiological functions that affect insulin, estrogen, androgen, prostaglandins, and immune function. This recommendation to include physical activity in one's lifestyle to reduce cancer risk is supported by a recent extensive review by the World Health Organization.
For people who are largely inactive or just beginning a physical activity program, a gradual increase to 30 minutes per day of moderate-to-vigorous physical activity on at least five days per week will provide substantial cardiovascular benefits and aid in weight control. Those who are already active at least 30 minutes on most days of the week should strive toward accumulating 45 minutes of moderate-to-vigorous activity on most days of the week.
Moderate activities are those that require effort equivalent to a brisk walk. Vigorous activities generally engage large muscle groups and cause an increase in heart rate, breathing depth and frequency, and sweating. These activities can be performed in a variety of settings: occupational, recreational, in the home or garden, and with friends or family. While there is limited evidence regarding whether physical activity is most protective if done in a single session or incrementally throughout the day, it is reasonable to assume that benefit can be accumulated in separate sessions of 20 to 30 minutes each. . .
Because one of the best predictors of adult physical activity is activity levels during childhood and adolescence, and because of the critical role physical activity plays in weight maintenance, children and adolescents should be encouraged to be physically active at moderate-to-vigorous intensities for at least 60 minutes per day on five or more days per week. Such activities should include sports and fitness activities at school and at home. To help achieve activity goals, daily physical education programs and activity breaks should be provided for children at school, and television viewing and computer game time should be minimized at home. . .
3. Maintain a healthful weight throughout life.
• Balance caloric intake with physical activity.
• Lose weight if currently overweight or obese.
Balancing Energy Intake and Expenditure
Overweight and obesity are associated with increased risk for cancers at several sites: breast (among postmenopausal women), colon, endometrium, adenocarcinoma of the esophagus, gallbladder, pancreas, and kidney. These findings are supported both by animal studies and by epidemiological studies.
The Body Mass Index (BMI) is an expression of weight-for-height calculated as body weight in kilograms divided by height in meters, squared. Exact cut-offs for BMI levels at elevated risk are difficult to define, since epidemiological studies have used different cutpoints in calculating cancer risks associated with body weight. However, experts consider a BMI within the range of 18.5 to 25.0 kg/m to be healthful, a BMI between 25.0 and 29.9 to be overweight, and a BMI of 30.0 and over to be obese (Figure 1 ). Individuals should strive to maintain a BMI between 18.5 and 25.0 kg/m2.
The best way to achieve a healthful body weight is to balance energy intake (food intake) with energy expenditure (physical activity). Excess body fat can be reduced by restricting caloric intake and increasing physical activity. Caloric intake can be reduced by decreasing the size of food portions and limiting the intake of calorie-dense foods high in fat and refined sugars (e.g., fried foods, cookies, cakes, candy, ice cream, and soft drinks). Such foods should be replaced with foods like vegetables and fruits, whole grains, and beans. People should be aware that meals served in restaurants typically exceed the portion sizes needed to meet recommended daily caloric intake. Physical activity as well as diet is essential for maintenance of a healthful weight.
. . . Even though our knowledge about the relationship between weight loss and cancer risk is incomplete, individuals who are overweight and obese should be encouraged and supported in their efforts to reduce weight. Obesity is a major risk factor not only for cancer, but also for diabetes, stroke, and coronary heart disease.
Because overweight in youth tends to continue throughout life, the increasing prevalence of overweight and obesity in pre-adolescents and adolescents may increase the incidence of cancer in the future. For these reasons, efforts to establish healthful weight, physical activity habits, and patterns of weight gain should begin in childhood.
4. If you drink alcoholic beverages, limit consumption.
People who drink alcohol should limit their intake to no more than two drinks per day for men and one drink a day for women. The recommended limit is lower for women because of their smaller body size and slower metabolism of alcohol. A drink of alcohol is defined as 12 ounces of beer, five ounces of wine, or 1.5 ounces of 80-proof distilled spirits. Alcohol consumption is an established cause of cancers of the mouth, pharynx, larynx, esophagus, liver, and breast. Alcohol consumption may also be related to increased risk of colon cancer. For each of these cancers, risk increases substantially with intake of more than two drinks per day. . . [R]egular consumption of even a few drinks per week has been associated with an increased risk of breast cancer in women. The mechanism by which alcohol is related to breast cancer is not known with certainty, but may be due to alcohol-induced increases in circulating estrogens or other hormones in the blood, reduction of folic acid levels, or to a direct effect of alcohol or its metabolites on breast tissue. Reducing alcohol consumption may be an important way for many women to reduce their risk of breast cancer. Some studies suggest that consuming the recommended amount of the vitamin folic acid can minimize the increased risk of breast cancer from alcohol, but this relationship has not been firmly established.
Tim Byers, MD, MPH, Marion Nestle, PhD, MPH, Anne McTiernan, MD, PhD, Colleen Doyle, MS, RD, Alexis Currie-Williams, MPH, CHES, Ted Gansler, MD, Michael Thun, MD and the American Cancer Society 2001 Nutrition and Physical Activity Guidelines Advisory Committee*
Dr. Byers is Professor, Preventive Medicine, University of Colorado Health Science Center, Denver, CO.
Dr. Nestle is Professor and Chair, Department of Nutrition and Food Studies, New York University, New York, NY.
Dr. McTiernan is Associate Member, Fred Hutchinson Cancer Research Center, Seattle, WA.
Ms. Doyle is Director, Nutrition and Physical Activity, American Cancer Society, Atlanta, GA.
Ms. Currie-Williams is Manager, Nutrition and Physical Activity, American Cancer Society, Atlanta, GA.
Dr. Gansler is Director of Medical Strategies, American Cancer Society, Atlanta, GA, and Editor of CA.
Dr. Thun is Vice President, Epidemiology and Surveillance Research, American Cancer Society, Atlanta, GA.
This is the website where you can read the full report: http://caonline.amcancersoc.org/cgi/content/full/52/2/92
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