Hormones in milk are a reason but not THE reason. The increase in the proportion of girls who are overweight before puberty, xenoestrogenic pollutants in our environment, low fiber in the diet, chemicals in hair-straightening treatments, and various other factors also contribute to a change in the AVERAGE age of first menstruation.
11-12 is a normal age, and it has been for about 60 years, ever since the improvements in nutritition that gradually brought the average age down from about 16 in the early 1800s. Your daughter is likely to start at about the same age you did, unless her dad's family are late bloomers.
If you want to try to keep your daughter from menstruating any earlier than genetics would dictate, hormone-free milk is a good idea, and an even better idea is to have a diet high in fiber and low in animal fats. Even the best milk contains pollutants that cows take in from the environment and concentrate in their milk (and meat).
As for mental readiness, you can work on that by teaching healthy attitudes toward menstruation from an early age and helping your daughter to feel prepared for it whenever it happens.
Mama to a boy EnviroKid
10 years old and a little girl EnviroBaby
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