Normal, healthy age at menarche under conditions of good nutrition without caloric excess falls somewhere between 15 and 18. But today in the U.S., about half of girls begin developing breasts before age 10, and the average age at menarche is less than 12 ½ and still declining.
About 16 percent of girls enter puberty by the age of 7, and about 30 percent by the age of 8. The number of girls entering puberty at these early ages has increased markedly since 1997. This is a disturbing trend.
Identifying the factors that push girls into early puberty remains a challenge. People always want to know the reason, but it is not possible to sort out the reason or the fix. It’s a lot of things interacting together, and they have different effects on different individuals.
Puberty starts when a hormone in the brain causes the pituitary gland to release more hormones. Luteinizing hormone (LH) and follicle-stimulating hormone (FSH) cause the ovaries to produce estrogen or testosterone, prompting physical changes.
The neurological and hormonal systems that regulate pubertal timing are complex, but research has identified a number of environmental factors that may be contributing to the decline in age at puberty.
There is a definite association between childhood obesity and earlier puberty in girls. Excess body fat alters the levels of the hormones insulin, leptin, and estrogen, and these factors are believed to be responsible.
Physical inactivity may decrease melatonin levels, which can also affect signals in the brain that trigger pubertal development.
Higher total protein, animal protein, and meat intake in children age 3-7 have been associated with earlier menarche. In contrast, higher vegetable protein intake at age 5-6 is associated with later menarche.
High protein intake elevates IGF-1 levels and promotes growth, which could accelerate the onset of puberty. Meat and dairy consumption in children may also reflect ingestion of environmental endocrine-disrupting chemicals (EDCs) that have accumulated in animal tissues.
The modern diet rich in processed foods, dairy, processed meats and fast food is disruptive to normal development and aging. Early puberty is an early sign of premature aging.
Exposure to EDCs are a major cause of early puberty. EDCs are endocrine-disrupting chemicals that either mimic, inhibit, or alter the action of natural hormones.
These chemicals are everywhere in our environment, present in a vast array of products including organochlorine pesticides, plastics, fuels, and other industrial chemicals. They are a threat to health to adults as well as children.
The substances of most concern currently are BPA and phthalates. BPA is used in the manufacture of polycarbonate plastics, such as rigid cups, water bottles and food storage containers.
Phthalates are chemicals used to make PVC plastics more flexible, and are found in a variety of products including toys, food packaging, hoses, raincoats, shower curtains, vinyl flooring, wall coverings, lubricants, adhesives, detergents, nail polish, hair spray, and shampoo.