Variety and moderation are not new messages. They were around in your mother's and grandmother's day. They're guiding principles for both the Dietary Guidelines for Americans and the Food Guide Pyramid. They also mean placing emphasis on diets consumed over several days, rather than on single meals or foods. Said another way, they mean feeling O.K. about splurging on Haggen Daz, as long as you're not making it a regular practice.
Some countries try to put a number on variety.
Japanese health officials recommend their people eat at least 20 different foods each day. It also proposes altering the size and location of meals as a way to help achieve even more variety. And, the number 20 did come up. When the number of different foods eaten daily exceeded 20, nutritional adequacy occurred almost automatically. Twenty different foods may be a piece of cake for a growing boy who spends his afternoon grazing your refrigerator.