The early onset of puberty in girls associated with animal protein consumption may be due to endocrine disrupting chemical pollutants in the meat supply.
Image thanks to kodomut
Early onset of puberty is considered a risk factor for a number of diseases in adulthood, including hormone-related cancers, a shorter lifespan, metabolic syndrome, and cardiovascular disease. The conventional thinking has been that the age of puberty has been getting earlier and earlier because our children have been getting fatter and fatter. Well our kids have been getting heavier, especially in the United States—we're #1! But while the age of a girl's first period has been dropping in the US and Asia, in Europe--despite their kids getting heavier too--there hasn't been a steady decline in puberty onset. So it may be less about how much kids are eating and more about what they're eating. The most consistent link between diet and premature puberty has been animal protein consumption. For example, every gram of daily animal protein intake—that's the weight of a paperclip—is association with a 17% increase in the risk of girls starting their periods earlier than age 12. Why this link between animal protein and premature puberty? Well we know meat increases the levels of the growth hormone IGF-1 and that alone is associated with early onset puberty, but maybe animal protein is just a proxy for the endocrine disrupting chemicals that build up the food chain in animal products. Recent reports found "significant associations between exposure to environmental pollutants and sexual maturation." This was done in Europe. In the U.S. a similar relationship was found with the flame retardant chemicals found in fish and chicken. "Over the last three decades, human exposure levels of these industrial pollutants in the U.S. have increased from virtually nonexistent to almost everyone carrying them around. They appear to have multiple adverse effects, but "of all the potential toxicities, endocrine disruption may be the major concern in children. And those with the most circulating in their bloodstream appeared up to 10 times more likely to start their period early. But since they're found most concentrated in the diet in fish and chicken maybe the level of these chemicals in their bloodstream is just kind of a proxy for meat consumption. Either way, more animal protein is associated with early onset puberty, whereas plant protein has the opposite effect "children with higher intakes of vegetable proteins start puberty 7 months later than average, and children eating more animal protein start puberty 7 months earlier than average. Soy seems most protective. "Girls with the highest levels of dietary isoflavone intake—the phytonutrients in soy foods--may experience their onset of breast development approximately 7–8 months later than girls with the lowest levels of intake." What effect might these shifts have on disease rates? Well "Delays in the timing of puberty in response to beneficial dietary habits (higher intakes of vegetable protein and soy, and lower intakes of animal protein) may be of substantial public health relevance: A later age of starting ones period is related to a reduced risk of breast cancer, and a later first period is associated with a lower total mortality, meaning a longer lifespan. Hence, a delay in the timing of puberty by approximately 7–8 months that is achievable with dietary modifications—either more plants or fewer animals--may translate into a 6% reduction in breast cancer risk and an up to 3% decrease in total mortality. And not just a problem in girls, boys eating more meat in childhood appear more likely to grow up with the kind of abdominal fat deposits that increase risk for heart disease.
To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring watch the above video. This is just an approximation of the audio contributed by Jonathan Hodgson.
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If you're not familiar with IGF-1, I have a series of videos about the growth hormone (though mostly in relation to cancer risk). See, for example, The Answer to the Pritikin Puzzle and Cancer-Proofing Mutation. And if you've never heard of "metabolic syndrome" I talk about it in Metabolic Syndrome and Plant-Based Diets. Is it possible to overdo soy? Yes, but you'd have to work at it: How Much Soy Is Too Much?
I talk more about endocrine disrupters in:
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