There's no doubt that young girls these days are maturing a lot faster than when we were little. On average, puberty is starting as young as 9 years in Caucasions and 8 years in African-Americans (and that's an average, so for some individuals, it starts much sooner). Just look at the bra section in Justice...it seems to get bigger each year.
A number of theories exist as to why this is happening, most notably the increase in childhood obesity. Young girls who are obese have a much higher risk of developing early versus non-obese peers. Fat cells produce estrogen, which may kick off the puberty process early. Young boys who are obese may have delayed puberty for the same reason...however the estrogen blocks testosterone from initiating puberty. Either way, those of you with children would probably agree that they are happiest when they are 'average'. Early puberty or late puberty does not make for a happy child and therefore by default, a happy parent.
Other theories for why puberty is starting earlier include things like pesticides, hormones in milk, and other contaminants in our environment. And it may not just be whether the children themselves are exposed to these contaminants, but both parents as well.
A new study this month is suggesting another possible cause for early puberty: low levels of vitamin D. The research showed that girls in northern latitudes (where there is much less sun and therefore less vitamin D being made in the skin) are more likely to have their first period earlier than those in southern latitudes. This is a very important finding because girls who have their first period before age 12 have a much higher risk of breast cancer later in life.
This study doesn't prove that taking a vitamin D supplement will delay a girl's first period, but it does provide more rationale for why its important for girls to drink milk (which has vitamin D) and/or take a multi-vitamin containing vitamin D. These results also suggest that children in northern climates may benefit from having vitamin D levels tested at the pediatrician's office to rule out a deficiency.
And most importantly (for me anyway), this is a darn good reason for a winter vacation in a nice climate!