Problems with the Pyramid
Print versions of the USDA's new food pyramid, MyPyramid, offer little or no specific information. The Web version, MyPyramid.gov, at least explains what the stripes mean. Your best bet is to start with "Inside the Pyramid".
The pyramid is supposed to be a direct translation of the Dietary Guidelines for Americans, which is updated every five years.
An alternative to the USDA's pyramid is one developed by Dr. Walter Willett and his colleagues at the Harvard School of Public Heath. The Healthy Eating Pyramid is based on the best science available. It is described in his book, Eat, Drink, and Be Healthy, which also gives the scientific basis for each of the Healthy Eating Pyramid's building blocks.