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Some say that early puberty in girls may be caused by what we eat.

Is there evidence of that?

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    What are you skeptical of? This is a researched and referenced article. – Chad Nov 30 '11 at 19:56
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    I'm skeptical of the very claim that puberty "starts earlier than it used to". In the past human beings began breeding at earlier ages than they do now, just depends on how far back you go... – jwenting Dec 1 '11 at 6:25
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    @jwenting: An interesting issue. Is 1840 far enough back? See Diagram 2 in the Plowden Report. If you want to go further back then that, then you could ask a new question - but you'd have to find someone making the corresponding claim. – Oddthinking Dec 1 '11 at 13:39
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    @Oddthinking: that graph only goes up to the '60s. In recent years the age of puberty is decreasing (at least in the US). See, for instance: ncbi.nlm.nih.gov/pubmed/16932041 . Then, it all depends how you define puberty, age of menarche has not decreased a lot apparently. ncbi.nlm.nih.gov/pubmed/16817811 – nico Dec 2 '11 at 9:24
  • @Nico: re: extend of the graph - yes, I cited that graph because it was the earliest date I could easily find, not the latest. Re: recent years - yes, a decreasing age of puberty is in keeping with the secular trend. Interesting point about puberty having multiple definitions. – Oddthinking Dec 2 '11 at 12:54
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TL;DR: This article has poorly constructed arguments. However, it does serve to provide references to support some association (not causation) between diet and early puberty.

First, let me summarise the key arguments in the linked article, just with regards to diet and precocious puberty, which is what the OP is asking about. (That is, I am ignoring claims about cancer, breastfeeding, mental health, etc.):

  1. One of two mentioned factors in precocious puberty is consumption of cow's milk (no reference provided).

  2. Cow's milk has a high fat content, and other bad things.

  3. These are all linked to early puberty.

  4. Hispanic child are less likely to consume cow's milk. (no reference provided). This argument peters out there. I see no actual claim that Hispanic children have later puberty as a result.

So, we can ignore statement 4. There is no reference for Statement 1 (or 4). I'm not going to argue Statement 2. The critical statement is statement number 3, and three references are provided. (Ref numbers #13, #14, and #15 in the article.) Let's look at those to see if they support the claim.


13: Stoll BA. Western diet, early puberty and breast cancer risk. Breast Cancer Res Treat (England) Jun 1998;49(3):187-93.

This paper is primarily about the increased breast cancer risk associated with early puberty. However, it does briefly summarise the purported causes of early puberty.

Improving nutrition is generally assumed to be responsible for the secular trend to ever-earlier onset of menarche in Western industrialised countries.

[...]

Nutritional factors are likely to be responsible and current option is that menarche is provoked by a critical accumulation of adipose tissue rather than through the effects of specific macronutrients [17]. Studies in the USA and Canada have found that earlier onset of menarche is associated with a greater height and weight for age and that after allowing for these variables, there was no association with energy-adjusted intake of fat, protein or carbohydrate in the diet [23, 24]. Nevertheless one prospective study in Germany concluded that a higher energy-adjusted fat intake was associated with accelerated menarche and might be responsible for earlier body fatness [25].


14: Outwater JL, et al. Dairy products and breast cancer: the IGF-I, estrogen and bGH hypothesis. Med Hypotheses Jun 1997;48(6):453-61.

There is not one but three problems with this paper.

First, it looks at breast cancer, not early puberty. It is off-topic for our discussion, but on-topic for the general article.

Second, it doesn't conclude anything useful for the article

In conclusion, despite several intriguing hypotheses linking dairy product consumption and breast cancer, the available epidemiologic evidence does not support a strong association between the consumption of milk or other dairy products and breast cancer risk.

Third, it is published in Med Hypotheses, which is a great place to get ideas for future experiments, but not a great place to link to to show that the evidence supports your argument. [More info]


15: Kato I, et al. Factors related to late menopause and early menarche as risk factors for breast cancer. Jpn J Cancer Res (Japan) Feb 1998;79(2):165-72.

This paper was focussed on breast cancer, but relied on surveys of 17,000 Japanese women older than 40 to gauge some of the factors involved in both puberty and menopause.

Note the weakness is asking someone about what happened thirty years earlier, and a dubious assumption that eating habits varied in strength but not in character over the subjects lives. I've not reported the borderline associations (e.g. p>0.05).

Positively correlated factors for early menarche included:

  • Residence in a metropolitan area
  • Height, weight and Body-Mass Index (BMI)
  • Daily intakes of bread, meat, fish, shellfish, egg, green-yellow vegetables, other vegetables, fruits, milk and black tea.

Inversely correlated were:

  • Large rice intake, daily miso soup, pickles.
  • Smoking (as an adult?!)

Conclusion

  • Adipose fat levels are believed to be a trigger for menarche, although none of the cited articles show that directly, and there is some mixed evidence.

  • A survey (of moderately weak power) suggests correlations (not causation) between a number of dietary elements and early menarche.

  • The linked article makes some dubious claims.

  • "Smoking (as an adult?!)" sadly there are girls smoking prior to puberty – Chad Dec 1 '11 at 17:46
  • @Chad: Agreed, but based on my understanding of their methodology, they ask "do you consume X now?" and assume you always did/didn't consume X, which seems particularly unsafe with smoking, drinking and Froot Loops. – Oddthinking Dec 1 '11 at 21:24
  • And milk, now that I think of it. – Oddthinking Dec 1 '11 at 21:24
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    Recently there's also been a proposed link between BPA exposure (both pre and post natal) and early onset of menarche. I'll have to go browsing for the publications I've read about it. – Darwy Dec 2 '11 at 8:28

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