If you read anything by Dr. John Lee - you will find that this is all too common in the USA. My Hispanic friend was appalled that young ladies were starting their mentrual cycles at around 8 or 9 in this country.
Dr. Lee says it is too many hormones in their bodies - specifically too much estrogen - also considered by one school of thought to be the culprit of breast cancer in our later years.
The research has been solid enough that I don't use bleach (causes estrogenic activity in the body), try to buy hormone free meat, do buy hormone free eggs, do not microwave in plastic, have gone to safer home care and personal care products (that work better and are less expensive by the way) to name the main things. Canada even tried to ban the sale of bleach because the research of estrogen and breast cancer connections were so strong.
My daughter was raised in a healthy home - not purist by any means, but healthy. She started her cycle at almost 15...and from what Dr. Lee teaches...that is healthier all the way around. That is a common age of the past...thus the huge Hispanic celetration at this age for young ladies...she is becoming a woman.
Dr. Lee has died :( but he spent the last years of his life trying to educate doctors that too much estrogen in the body is the culprit for many whoas women have - PMS, menopausal, etc. It's out of balance with progesterone and that's the root of the problems.