New Dietary Guidelines Could Reduce Cancer Risk

Roxanne Nelson

February 04, 2011

February 4, 2011 — New dietary guidelines issued by the US Department of Agriculture (USDA) have taken aim at the growing waistlines of Americans. They have been welcomed by cancer experts, who believe that adherence to them could significantly reduce cancer risk.

Currently in the United States, more than two thirds of adults and one third of children are obese or overweight. The new guidelines place a more pronounced emphasis on reducing caloric intake and increasing physical activity, and recommend increasing the intake of fruit, vegetables, whole grains, and fiber.

The USDA guidelines echo the advice of the American Institute for Cancer Research (AICR) and overlap much of the guidelines on nutrition and physical exercise issued by the American Cancer Society (ACS), although there is one notable difference between them.

The USDA guidelines do not recommend limiting red and processed meats, whereas the ACS recommendations for cancer prevention do. This recommendation was made on the basis of a wealth of studies showing increased colorectal cancer risk, explained Marji McCullough, ScD, RD, strategic director of nutritional epidemiology at ACS.

However, there are many similarities. Both sets of guidelines place "a strong emphasis on achieving and maintaining a healthy body weight," Dr. McCullough told Medscape Medical News.

In addition, the USDA recommendation for a "total dietary pattern containing a variety of vegetables, cooked dry beans and peas, fruits, whole grains, nuts, and seeds is consistent with our own recommendations," Dr. McCullough noted.

"Given the extraordinary increase in obesity in the United States and compelling evidence that excess body weight increases the risk of many types of cancer, we fully support the USDA's efforts to address this important public health issue," Dr. McCullough said.

Highlights of the Guidelines

The USDA guidelines stress the need to maintain appropriate calorie balance during each stage of life — childhood, adolescence, adulthood, pregnancy and breastfeeding, and older age.

The recommendations include:

  • Increasing vegetable and fruit intake and consuming a variety of vegetables, especially dark-green, red, and orange vegetables and beans and peas.

  • Consuming at least half of all grains as whole grains and increasing whole-grain intake by replacing refined grains with whole grains.

  • Choosing a variety of foods high in protein, including seafood, lean meat and poultry, eggs, beans and peas, soy products, and unsalted nuts and seeds.

  • Selecting foods that provide more potassium, dietary fiber, calcium, and vitamin D.

  • Reducing daily sodium intake to less than 2300 mg; for certain populations (e.g., people 51 years and older; blacks; and those with hypertension, diabetes, or chronic kidney disease), sodium intake should not exceed 1500 mg per day.

  • Keep trans fatty acid consumption as low as possible by limiting foods that contain synthetic sources of trans fats, such as partially hydrogenated oils, and by limiting other solid fats.

  • If alcohol is consumed, it should be consumed in moderation — up to 1 drink per day for women and 2 drinks per day for men — and only by adults of legal drinking age.

Echoes Advice From AICR

The USDA guidelines echo the advice of the AICR to lower cancer risk, said Susan Higginbotham, RD, PhD, director of research at the AICR, in a statement. "We're thrilled to see obesity prevention, and thus cancer prevention, being placed front and center, where it belongs."

The AICR estimates that more than a third of common cancers could be prevented if individuals adhered to a healthy diet, increased their level of physical activity, and stayed lean. They note that excess weight has been linked to cancers of the colorectum, esophagus, endometrium, kidney, pancreas, and postmenopausal breast. In addition, there is some evidence linking the risk for gallbladder cancer to being overweight or obese.

The USDA guidelines also place emphasis on the need to consume a plant-based diet. "For years, the science on cancer risk has shown that diets emphasizing a variety of vegetables, fruits, whole grains, and beans are cancer-protective," Dr. Higginbotham said. "A plant-based diet means moderating meat intake, not eliminating it altogether."

Dr. Higginbotham notes that in many of the early news reports on the USDA guidelines, the focus was on the recommendation to reduce sodium intake. "We agree that Americans are getting more salt than they need," she said, "but one of the bonuses of eating a plant-based diet is getting more unprocessed foods, and that means less sodium."

In 2007, the AICR and the World Cancer Research Fund published what is considered to be the most comprehensive scientific analysis of cancer prevention and causation ever undertaken. It showed convincing evidence that excess weight and obesity can increase the risk for a number of cancer types. An updated 2009 version of that report confirmed that lifestyle factors play a significant role in the risk for breast cancer. The report reaffirmed that factors such as maintaining a healthy weight, breastfeeding, exercising regularly, and limiting consumption of alcoholic beverages can reduce the risk for breast cancer.

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