Comments on the 2005 Dietary Guidelines
by Walter Willett, M.D., Dr. P.H.
Harvard's Dr. Walter Willett
Every five years, the U.S. Department of Agriculture taps an expert panel of nutritionists, epidemiologists, food scientists, and others to revise the Dietary Guidelines for Americans. According to the USDA, the guidelines "provide authoritative advice for people two years and older about how good dietary habits can promote health and reduce risk for major chronic diseases. They serve as the basis for Federal food and nutrition education programs" (USDA, 2005).
The newest version, released in early January 2005, reflects the tense interplay of science and big business. In general, it is an improvement over previous editions. Dietary Guidelines for Americans 2005 emphasizes the importance of controlling weight and exercising, which were not given adequate attention in previous guidelines. It also makes a clear break from the past, where all fat was considered bad and the carbohydrate was the poster child of nutrients.
The new guidelines emphasize replacing saturated fat and trans fat with unsaturated fats, which have positive health value, and urge us to avoid trans fats. They also make important distinctions about carbohydrate sources. Instead of emphasizing "complex carbohydrates," a term that has little biological meaning, the new guidelines warn us to limit sugar intake and stress the benefits of whole grains. However, they also say it is fine to consume half of our grains as refined starch. That's a shame, since refined starches behave like sugar. They add empty calories, have adverse metabolic effects, and increase the risks of diabetes and heart disease.
Two giant agribusinesses scored points in the new guidelines. The meat industry continues to gain from the lumping together of red meat, poultry, fish, and beans, including soy products, as has been the case in previous guidelines. The guidelines ask us to judge these protein sources by their total fat content. This ignores the evidence that these foods have different types of fats and that there are benefits from replacing red meat with a combination of fish, poultry, beans, and nuts.
The dairy industry is the other big winner with the recommendation to consume three glasses of low-fat milk or other dairy products per day to prevent osteoporosis. Of all the recommendations, this one represents the most radical change from current dietary patterns. Three glasses of low-fat milk adds nearly 400 calories a day, which is a real issue for those trying to control their weight. In addition, millions of Americans are lactose intolerant, meaning even small amounts of milk or dairy products give them stomachaches, gas, or other problems. As described earlier in "Calcium—No Emergency" (in the "Drink to Your Health" section), taking in plenty of dairy products doesn't reduce the risk of fractures. It may, however, increase the risk of ovarian cancer or prostate cancer.
The final answer is not yet clear about the optimal intake of dairy products, but we should have strong evidence of safety before promoting radical dietary changes. Dairy products are certainly not an essential component of a healthy diet, as the guidelines would have us believe.