Different people has different needs

Because different bodies require different amounts of nutrients, RDAs currently address as many as 22 specific categories of human beings: boys and girls, men and women, from infancy through middle age. The RDAs recently were expanded to include recommendations for groups of people ages 50 to 70 and 70 and older. Eventually, recommendations will be made for people older than 85. These expanded groupings are a really good idea. In 1990, the U.S. Census counted 31.1 million Americans who are older than 65. By 2050, the U.S. Government expects more than 60 million to be alive and kickin’.

You wouldn’t want these baby boomers to miss their RDAs, now would you? But who you are affects the recommendations. If age is important, so is gender. For example, because women of childbearing age lose iron when they menstruate, their RDA for iron is higher than the RDA for men. On the other hand, because men who are sexually active lose zinc through their ejaculations, the zinc RDA for men is higher than the zinc RDA for women. Finally, gender affects body composition, which influences RDAs.

Consider protein: The RDA for protein is set in terms of grams of protein per kilogram (2.2 pounds) of body weight. Because the average man weighs more than the average woman, his RDA for protein is higher than hers. The RDA for an adult male, age 19 or older, is 56 grams; for a woman, it’s 46 grams.