Even when the old pyramid was adopted nutrionalists knew that it was inaccurate. The problems:
Research indicated that although saturated and trans fats contributed to heart disease, the consumption of unsaturated lipids reduce the chance of heart disease. Lipids needed to be divided into two different categories.
The protein rich foods that we eat also vary in their effects. Poultry and fish contain less saturated fat and more unsaturated fat than red meat does and studies have shown that people who replace red meat with chicken and fish have a lower risk of coronary heart disease and colon cancer. Also nuts, which some people thought should be avoided because of their high lipid content, have been shown to improve blood cholesterol and lower the risk of heart disease and diabetes. People who eat nuts are actually less likely to be obese; perhaps because nuts are more satisfying to the appetite, eating them seems to have the effect of significantly reducing the intake of other foods.
Likewise all carbohydrates do not affect our bodies the same way. Starch in refined grains (such as white flour) and potatoes act similar to simple sugars. They cause a rapid increase in glucose (blood sugar) that stimulates a large release of insulin which then drops glucose dramatically. This "yo-yo" action contributes to cardiovascular disease, diabetes (Type 2), and to overeating and obesity. Whole grain foods are high in fiber and lower the risk of these problems.
In addition three new concepts were added to the pyramid:
- The concept of exercise was added because a good diet alone is not enough for good health.
- Most Americans would benefit from a multivitamin.
- Limited amounts of alcohol are "heart healthy" for most people. One drink per day is usually the reccomended amount. One serving is usually defined as 12 ounces of beer, 5 ounces of wine, or 1 ½ ounces of hard liquor.
This point has brought about a HUGE amount of criticism from a variety of sources including Mothers Against Drunk Drivers, some church groups and many of the organizations that seek to stop teen drinking .
Despite the popularity of the Harvard pyramid with many of the professionals who study diet issues it was not adopted as the official new pyramid. The U.S. Department of Agriculture developed their own.
Most of this text is from “Rebuilding the Food Pyramid” Scientific American, January 2003. You can read the full text at www.sciam.com.