In 2005 the U.S. Department of Agriculture officially released its newest Food Guide Pyramid, which was intended to help the American public make dietary choices that would maintain good health and reduce the risk of chronic disease.
The new pyramid attempts to provide individualized advice based on a person's age, gender and level of physical activity. It focuses on the consumption of grains, meat and beans, milk, vegetables, fruit, and oils.
The 2005 pyramid replaced a 1992 USDA pyramid that differed from it in several respects. The new pyramid provides more emphasis on whole grains and physical activity. It does not, however, solve all the problems associated with its predecessor, because it still places too much emphasis on grains and milk and does not sufficiently emphasize the adverse effects of some types of fat. Unlike the old pyramid's graphic representation, which showed the proportions of various foods that should be consumed as stacked layers of different sizes, the 2005 pyramid conveys no information about nutrition; it simply shows a figure ascending a rainbow-colored staircase [see box on page 17].
We have drawn up a revised pyramid that better reflects the current evidence regarding the relation between diet and health. Studies indicate that adherence to the recommendations in our revised pyramid can significantly reduce the risk of cardiovascular disease for both men and women.
The Old Food Pyramid
THE USE OF IMAGES to promote dietary advice goes back nearly a century in the U.S. The recommendations embodied in the 1992 pyramid were widely adopted, and the image became an icon. The basic advice was that people should minimize their consumption of fats and oils but should eat six to 11 servings a day of foods rich in complex carbohydrates--bread, cereal, rice, pasta and so on. The food pyramid also recommended generous amounts of vegetables (including potatoes, another plentiful source of complex carbohydrates), fruit and dairy products, and at least two servings a day from the meat and beans group, which lumped together red meat with poultry, fish, nuts, legumes and eggs.
Even when the pyramid was being developed, though, nutritionists had long known that some types of fat are essential to health and can reduce the risk of cardiovascular disease. Furthermore, scientists had found little evidence that a high intake of carbohydrates is beneficial. After 1992 more and more research showed that the USDA pyramid was grossly flawed. By promoting the consumption of all complex carbohydrates and eschewing all fats and oils, the pyramid provided misleading guidance. In short, not all fats are bad for you, and by no means are all complex carbohydrates good for you.
How did the original USDA pyramid go so wrong? In part, nutritionists fell victim to a desire to simplify their dietary recommendations. Researchers had known for decades that saturated fat--found in abundance in red meat and dairy products--raises cholesterol levels in the blood. High cholesterol levels, in turn, are associated with a high risk of coronary heart disease (heart attacks and other ailments caused by the blockage of the arteries to the heart). In the 1960s controlled feeding studies, in which the participants ate carefully prescribed diets for several weeks, substantiated that saturated fat increases cholesterol levels. But the studies also showed that polyunsaturated fat--found in vegetable oils and fish--reduces cholesterol. Thus, dietary advice during the 1960s and 1970s emphasized the replacement of saturated fat with polyunsaturated fat, not total fat reduction.
The notion that fat in general is to be avoided stems mainly from observations that affluent Western countries have both high intakes of fat and high rates of coronary heart disease. This correlation, however, is limited to saturated fat. Societies in which people eat relatively large portions of monounsaturated and polyunsaturated fat tend to have lower rates of heart disease [see box on page 21].