Meat, animal protein, and soymilk (soya milk) can affect premature breast development in girls.
Do dairy products contribute to increased mucus (phlegm) production?
The age of puberty for girls continues to decline. Last year researchers published a study of more than a thousand girls across the country and found a “a higher prevalence of onset of breast development among girls at ages 7 and 8 years old compared with those observed more than just a decade earlier."
This has obvious psychosocial implications, but from a medical point of view, the reason we're so concerned is that those who start developing at a younger age are at an increased risk of breast cancer later in life, due to the increased estrogen exposure. For every year puberty can be delayed, risk of future breast cancer may drop 7%. A century a go, girls were starting their periods at around 16, which may help explain why breast cancer is now such an epidemic.
So what’s contributing to this premature development? New study last year following 3,000 girls found the single most important dietary determinant was how much meat girls eat. “Meat intake, measured, at 3 and 7 years was strongly positively associated with starting their period by 12 years 8 months, so the trends in "age at menarche" in the West over the last century might reflect the trends in meat consumption.” The second most powerful predictor was animal protein in general, so it wasn't just meat.
The reason girls eating vegetarian have been found to develop more normally may also be influenced by their soy intake. Last year a group of German researchers calculated that girls drinking just like two cups of soymilk a week developing breasts on average 8 months later than those who drank hardly any. Soy failed to have an effect, however, on timing in puberty in boys.
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 Dianne Moore.
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Biro FM, Galvez MP, Greenspan LC, Succop PA, Vangeepuram N, Pinney SM, Teitelbaum S, Windham GC, Kushi LH, Wolff MS. Pubertal assessment method and baseline characteristics in a mixed longitudinal study of girls. Pediatrics. 2010 Sep;126(3):e583-90.
Clavel-Chapelon F; E3N-EPIC Group. Differential effects of reproductive factors on the risk of pre- and postmenopausal breast cancer. Results from a large cohort of French women. Br J Cancer. 2002 Mar 4;86(5):723-7.
Rogers IS, Northstone K, Dunger DB, Cooper AR, Ness AR, Emmett PM. Diet throughout childhood and age at menarche in a contemporary cohort of British girls. Public Health Nutr. 2010 Dec;13(12):2052-63.
Related videos on premature puberty include Hormones in Skim vs. Whole Milk and Xenoestrogens & Early Puberty. And there's more than a dozen videos on soy, including Soy & Breast Cancer and Soy & Breast Cancer Survival.
You may also be interested in my blog posts for more context on the topic: Breast Cancer and Diet, Soy and breast cancer: an update, How Much Soy Is Too Much?, and Why Are Children Starting Puberty Earlier?
Soymilk (soya milk) should be shaken before pouring to get at the calcium that settles to the bottom.
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