In the U.S., girls are entering puberty at younger ages than they were 30 years ago. It is unclear why this is happening, although there are many hypotheses. Many believe that childhood obesity—which has also risen dramatically over that time frame—may lead to earlier onset of puberty for girls, as puberty tends to occur earlier in heavier girls. Some people point to specific foods and components, such as hormones in milk, for this down-aging of puberty. However, this is not supported by the facts:
- Children who consume more milk tend to have lower, rather than higher, body weights.1 If obesity is linked to early puberty, it is unlikely that milk plays a role.
- Today's adolescent girls drink less milk than their mothers did, not more.2 Thus, it is unlikely that milk is responsible for any change in the age at which girls enter puberty.
- Milk has always contained natural bovine growth hormones (BST) in very small amounts. Some dairy producers administer the synthetic version of this hormone (rBST) to increase milk production in their cows. FDA has concluded that milk produced by treated and untreated cows is exactly the same. 90 percent of these hormones are destroyed with pasteurization. The remaining trace amounts are broken down into inactive fragments in the gut. Both hormones are "cow specific" and have no effect on the human body.3 Thus, 'hormones in milk' is not a valid explanation for early puberty.
Milk is a significant source of calcium and should not be eliminated during the adolescent years. Preteen and teenager girls (age 9 -18) need 1,300 mg of calcium a day since this is the "window of opportunity" when calcium is deposited in bone. The U.S. Dietary Guidelines recommend that adolescent girls consume three cups of milk or dairy foods per day.4
1Moore LL. J Am Coll Nutr 2008;27(6):702-10
2Kaplowitz PB. Pediatrics 2008; 121(supp 3):208S.
3 Vicini J et al. J Am Diet Assoc 2008; 108:1198.
4Dietary Guidelines for Americans 2010, 7th ed, 2010.