Transcript: Protein, Puberty, & Pollutants
Below is an approximation of this video’s audio content. To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video.
“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 reason the age of puberty has been getting earlier and earlier is 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, maybe it’s 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—has been associated with about 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 over in Europe. In the U.S., a similar relationship was found with the flame-retardant chemicals, for example, which are found mostly in poultry and fish, unless you’re eating cat food.
“Over the last three decades, human exposure [to these levels of industrial pollutants] in the U.S. have increased from virtually nonexistent to [almost everyone carrying them around now].” They appear to have multiple adverse effects, but of all the potential toxicities, endocrine disruption (meaning hormonal disruption) may be the main concern in children. Girls with the most circulating in their bloodstream appeared up to ten times more likely to start their periods early.
But, since these chemicals are found most concentrated in fish and chicken, maybe the level of these chemicals in their bloodstream is just kind of a proxy for their meat consumption. Whatever the reason, animal protein intake is associated with early-onset puberty, whereas plant protein has the opposite effect. Children with higher levels of vegetable proteins starting puberty seven months later than average, and children eating more animal protein may start puberty seven months earlier than average.
Soy seems most protective. “[G]irls with the highest levels of dietary isoflavone intake [the phytonutrients in soy foods] may experience their onset of breast development…approximately 7 or 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 one’s period is related to a reduced risk of breast cancer, and a later first period is associated with lower total mortality (meaning a longer lifespan).”
Hence, “a delay in the timing of puberty by approximately 7-8 months,” which is “achievable with dietary modifications”—either more plants or fewer animals—”may translate into about a 6% reduction in breast cancer risk,” and up to a 3% decrease in total mortality. And, it’s not just a problem in girls; boys eating more meat in childhood appear to be more likely to grow up with the kind of abdominal fat deposits that increase risk for heart disease.
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