WLC Director of Nutrition Kathleen Zelman investigates the link between diet and cancer
By Kathleen Zelman, MPH, RD, LD
WebMD Weight Loss Clinic
Reviewed By Michael W. Smith, MD
Science is evolutionary, not revolutionary. While a new day often brings a new study looking at the link between cancer and diet, a single study rarely turns the world upside down. WebMD turned to experts to get to the bottom of the connection between cancer and nutrition.
"The evidence on fruits and vegetables has weakened over the last few years with respect to breast cancer yet remains strong for other forms of cancer such as respiratory and gastrointestinal cancers," Tim Byer, MD, tells WebMD. "There is no doubt that a diet rich in fruits and vegetables continues to be beneficial for cancer prevention in general."
"Regular physical activity, weight control, and a heart-healthy diet are the best defenses for both men and women to prevent disease and promote a long and healthy life," says Byer, epidemiologist and professor of preventive medicine at University of Colorado School of Medicine.
Food, Genetics Interact
There are a whole host of benefits of a healthy diet that go beyond cancer. Fruits, vegetables, and whole grains -- the foundation of a healthy diet -- contain fiber, antioxidants, phytochemicals, and other healthy substances. These nutrient-dense foods are naturally fat free, very satisfying, low in calories, and the cornerstone of a weight-control eating plan.
Food interactions are very complex. Healthful substances in food continue to be discovered. Researchers are unraveling the mystery of exactly which components in foods are responsible for preventing cancer and other chronic diseases.
In addition to foods themselves, our own unique genetic profile determines how our body responds to health-promoting substances in foods. To get the health protection and disease prevention benefits from food, experts recommend eating a wide variety of plant-based foods.
Back to Basics
Years ago, the American Cancer Society moved away from making recommendations on specific foods to reduce cancer risk to an emphasis on improving dietary patterns.
"Clearly, some foods are more beneficial than others, and we continue to advocate five servings a day of colorful fruits and vegetables" Colleen Doyle, MS, RD, American Cancer Society nutrition and physical activity director, tells WebMD.
Doyle adds that physical activity and weight control are just as important as a diet rich in fruits, vegetables, and whole grains and limited in saturated fat.
The strongest evidence for cancer prevention lies in weight management and regular physical activity, according to Doyle. "Following the guidelines for alcohol (1 drink/day for women, 2 for men) and not smoking are also essential to wellness and disease prevention."
Americans are overweight; 64% of adults are classified as overweight or obese, according to the CDC. Losing weight and getting regular physical activity may just be the magic bullet in cancer and disease prevention.
According to the American Institute for Cancer Research, a thorough review of existing scientific studies shows that obesity is a factor in some of the most common cancers.
"Obese individuals are at risk for certain types of cancer," Wahida Karmally, PhD, RD, Columbia University associate research scientist and director of nutrition, tells WebMD. She urges Americans to lose weight with a diet rich in fruits and vegetables because they are a powerhouse of antioxidants and help people feel full, so they eat fewer calories.
"We have strong evidence that a healthy diet containing lots of fruits and vegetables is beneficial to good health and can reduce risk for cancer, high blood pressure, heart disease, diabetes, stroke, arthritis, and others," says Karmally.
The American Cancer Society, American Heart Association, and American Diabetes Association, have launched a joint program called Everyday Choices to help Americans reduce their risk of cancer, diabetes, heart disease, and stroke. The program advocates the importance of a healthy diet, weight control, regular physical activity, avoiding smoking, and regular checkups with a health care provider. The trio of well-respected health organizations recommends a diet that includes:
- At least five servings a day of colorful fruits and vegetables. The richer the color, the more abundant the antioxidants.
- Limit intake of saturated fats and cholesterol by choosing seafood, poultry, lean meat and pork, beans, soy, and low-fat dairy products.
- Control portion sizes, especially foods high in fat and sugar.
- Use methods of cooking that are lower in fat such as baking, broiling and grilling.
- To lose weight, eat fewer calories and exercise regularly -- at least 30 minutes a day.
The American Institute for Cancer Research offers this list of tips to lower cancer risk in addition to not smoking or using tobacco in any form:
- Choose a diet rich in a variety of plant-based foods
- Eat plenty of fruits and vegetables
- Maintain a healthy weight and be physically active
- Drink alcohol in moderation, if at all
- Select foods low in fat and salt
- Prepare and store foods safely
Putting It All Together
Don't throw out the salad spinner. Whether you are trying to prevent cancer, lose weight, or promote heart health, the advice for a healthy diet remains the same. The best advice to lower cancer risk is to eat a plant-based diet, increase physical activity, maintain a healthy weight and don't smoke. Food is not a panacea to cure everything that ails you. A commitment to a healthy diet, weight control, and regular physical activity is the winning combination for disease protection and good health.
SOURCES: Tim Byer, MD, professor of preventive medicine, University of Colorado School of Medicine. Colleen Doyle, MS, RD, nutrition and physical activity director, American Cancer Society. Wahida Karmally, PhD, RD, associate research scientist and director of nutrition, Columbia University. CDC. American Institute for Cancer Research.