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The Food Pyramid
One approach to publicizing healthful food selection was the development of the Food Guide Pyramid, a graphic display that focuses on a diet sufficient in nutrients but without excesses (Figure 24.2). The goal was to use a well-chosen diet to promote good health. To avoid confusion, the development of this scheme had to take into account the fact that many people were familiar with the older recommendations about food groups.
The newer recommendations pay particular attention to increasing the amount of fiber and decreasing the amount of fat in the typical diet. Variety and moderation were key concepts of the graphic presentation. From the biochemical point of view, these recommendations translate into a diet based primarily on carbohydrates, with enough protein to meet needs for essential amino acids. Note that in Figure 24.2, carbohydrates are the base, with the correct amount suggested to be 6 to 11 servings of foods rich in complex carbohydrates, such as bread, cereal, rice, or pasta. Lipids should not contribute more than 30% of daily calories, but the typical American diet currently is about 45% fat. High-fat diets have been linked to heart disease and to some kinds of cancer, so the recommendation about lipid intake is of considerable importance.
Many scientists are questioning some of the details of the food pyramid. Certain types of fat are essential to health and actually reduce the risk of heart disease. Also, there has been little evidence to back up the claim that a high intake of carbohydrates is beneficial. Many people feel that the original food pyramid, which was published in 1992, has serious flaws. It overglorifies carbohydrates while making all fats out to be the bad guys. In addition, meat, fish, poultry, and eggs are all lumped together as if they are equivalent in terms of health. Plenty of evidence links saturated fat with high cholesterol and risk of heart disease, but monounsaturated and polyunsaturated fats have the opposite effect. Although many scientists knew the distinction between the various types of fat, they felt that the average person would not understand them, and so the original pyramid was designed to send the simple message that fat was bad. The implied corollary to fat being bad was that carbohydrates were good. However, after years of study, no evidence can be shown that a diet that has 30% or fewer calories coming from fat is healthier than one with a higher level.
To further complicate matters, we have to recall the effects of the traveling forms of cholesterol—the lipoproteins. Having high levels of cholesterol trav-eling as high-density lipoproteins (HDL) has been correlated with a healthy heart, while having high levels of cholesterol traveling in the form of low-density lipoproteins (LDL) is related to high risk of heart disease. When calories from saturated fat are replaced by carbohydrates, the levels of LDL and total cholesterol decrease, but so does the level of HDL. Because the ratio of LDL to HDL does not decrease significantly, there is little health benefit. However, the increase in carbohydrate has been shown to increase fat synthesis because of increases in insulin production. When calories from unsaturated fat are replaced with calories from carbohydrates, the results are even worse. The LDL levels rise in comparison with the levels of HDL.
Figure 24.3 shows a more modern view of a food pyramid that takes into account the most recent evidence and recommendations from some nutri-tionists. Note that at the base of the pyramid is the heart and soul of good health—exercise and weight control. There is no replacement for being active and for restricting total calories when it comes to staying healthy.
The next level up shows that the good types of carbohydrates and the good forms of fats occupy a prime location. Whole-grain foods are complex car-bohydrates that are digested more slowly, so they do not have the effect of raising blood glucose and causing insulin levels to rise to the extent that refined carbohydrates like white rice and pasta do. The healthy fats come from plant oils. Vegetables and fruits still occupy an important place in this pyramid, with nuts and legumes just above them. Next are good sources of protein, such as fish, poultry, and eggs. Note that the recommendation says zero to two servings. This is a change in approach, in that the type of protein is considered important and in the fact that the guide shows that it is not necessary to eat animal protein at all. Dairy products are found high up on the new pyramid. This is because, despite the commercials that sug-gest “everybody needs milk,” there are some noted health risks in consum-ing dairy products. Some cultures that consume large quantities of dairy products have the highest incidence of heart disease, probably due to the high concentrations of saturated fatty acids in milk and butter. In addition, many adults are allergic to milk proteins, and many are unable to digest lactose. At the peak of the pyramid are the items to be eaten only sparingly: red meat and refined carbohydrates, as well as some natural carbohydrate sources, such as potatoes. In April 2006, the U.S. Department of Agriculture launched a nutrition website at www.mypyramid.gov. This service allows individuals to find information about foods and the role of physical activity in order to make choices for a healthful lifestyle. The website includes inter-active programs to help people assess their lifestyle and nutrition choices, including worksheets to record daily consumption of nutrients.
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