[Lurker]

A diet higher in protein leads to increased growth rates, and better immunity--not things to be avoided.

No they are not. But nothing has only one side. Increased growth rates mean an earlier onset of menarch and with that an earlier interest in....other things. Personally I think all this stuff about chemicals, hormones, and mares placentas are a bunch of hogwash. American kids get access to more high quality animal and plant proteins than any other society on the planet. Hell, they get more protein than almost any society in history.

It's no wonder they mature faster and grow larger than their parents. One need only look at the children of immigrants to see the evidence.

L

[VanShuyten]

There's clear evidence that females who have any kind of nutritional deficiency, caloric or otherwise, have later onset of periods. The same goes for women who are challenged by disease or parasitism. In developed countries, women who train for extreme sports often "lose" their menstrual cycles, due to the nutritional stress of training for those events.

It would make sense that women who are well-fed and under little stress would start to menstruate earlier.