豆を食べると精子が半減?

豆を含む食物で精子が半減
 豆腐、醤油などの食物の中の植物エストロゲンがホルモンシグナルを妨げるかもしれないという。しかしアジアの人たちのほとんどが豆ベースの製品を食べているが不妊症は問題となっていない。
 「正常な」精子濃度は1ミリリットルあたり平均8000万~1億2000万で、隔日に豆ベースの食物の一部を食べた人の平均は4100万程度だった。
 豆の中のイソフラボンと呼ばれる化学薬品が精子生産に影響しているかもしれない。肥満の人がこの効果がより出やすいようであった(それは、体脂肪が高いとエストロゲン生産を増大する可能性があるという事実を反映するかもしれない)。
 食物または環境中のエストロゲン化合物は長い間関心が持たれていたけれども、最も危険な状態にいたのが誕生前の子宮内の男児である。
--------------------------------------------------
Page last updated at 23:07 GMT, Wednesday, 23 July 2008 00:07 UK
Soy foods 'reduce sperm numbers'
http://news.bbc.co.uk/2/hi/health/7519459.stm

画像Soy products
Soy products contain chemicals mimicking female hormones

A regular diet of even modest amounts of food containing soy may halve sperm concentrations, suggest scientists.

The study, published in the journal Human Reproduction, found 41 million fewer sperm per millilitre of semen after just one portion every two days.

The authors said plant oestrogens in foods such as tofu, soy mince or milk may interfere with hormonal signals.

However, a UK expert stressed that most men in Asia eat more soy-based products with no fertility problems.


Oestrogenic compounds in food or the environment have been of concern for a number of years, but we have mostly thought that it was boys exposed in the uterus before birth who were most at risk
Dr Allan Pacey
Sheffield University

Animal studies have suggested that large quantities of soy chemicals in food could affect fertility, but other studies looking at consumption in humans have had contradictory findings.

The Harvard School of Public Health study looked at the diets of 99 men who had attended a fertility clinic with their partners and provided a semen sample.

The men were divided into four groups depending on how much soy they ate, and when the sperm concentration of men eating the most soy was compared with those eating the least, there was a significant difference.

The "normal" sperm concentration for a man is between 80 and 120 million per millilitre, and the average of men who ate on average a portion of soy-based food every other day was 41 million fewer.

Dr Jorge Chavarro, who led the study, said that chemicals called isoflavones in the soy might be affecting sperm production.

These chemicals can have similar effects to the human hormone oestrogen.

Dr Chavarro noticed that overweight or obese men seemed even more prone to this effect, which may reflect the fact that higher levels of body fat can also lead to increased oestrogen production in men.

Worried men

However, the study pointed out that soy consumption in many parts of Asia was significantly higher than even the maximum found in these volunteers.

Dr Allan Pacey, a senior lecturer in andrology from the University of Sheffield, said that if soy genuinely had a detrimental effect on sperm production, fertility might well be affected in those regions, and there was no evidence that this was the case.

"Many men are obviously worried about whether their lifestyle or diet could affect their fertility by lowering their sperm count.

"Oestrogenic compounds in food or the environment have been of concern for a number of years, but we have mostly thought that it was boys exposed in the uterus before birth who were most at risk.

"We will have to look at adult diet more closely, although the fact that such large parts of the world have soy food as a major part of their diet and don't appear to suffer any greater infertility rates than those on western diets suggests that any effect is quite small."

------------------------------------------------
Hum. Reprod. Advance Access published online on July 23, 2008
Human Reproduction, doi:10.1093/humrep/den243
http://humrep.oxfordjournals.org/cgi/content/abstract/den243v1

© The Author 2008. Published by Oxford University Press on behalf of the European Society of Human Reproduction and Embryology. All rights reserved. For Permissions, please email: journals.permissions@oxfordjournals.org

Soy food and isoflavone intake in relation to semen quality parameters among men from an infertility clinic
Jorge E. Chavarro1,2,7, Thomas L. Toth3, Sonita M. Sadio4 and Russ Hauser3,5,6

1 Department of Nutrition, Harvard School of Public Health, 665 Huntington Ave., Boston, MA, USA 2 Channing Laboratory, Department of Medicine, Brigham and Women’s Hospital and Harvard Medical School, Boston, MA 02115, USA 3 Vincent Memorial Obstetrics and Gynecology Service, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA 4 Department of Urology, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA 5 Department of Environmental Health, Harvard School of Public Health, Boston, MA, USA 6 Department of Epidemiology, Harvard School of Public Health, Boston, MA, USA

7 Correspondence address. Tel: +1-617-432-4584; Fax: +1-617-432-2435; E-mail: jchavarr@hsph.harvard.edu

BACKGROUND: High isoflavone intake has been related to decreased fertility in animal studies, but data in humans are scarce. Thus, we examined the association of soy foods and isoflavones intake with semen quality parameters.

METHODS: The intake of 15 soy-based foods in the previous 3 months was assessed for 99 male partners of subfertile couples who presented for semen analyses to the Massachusetts General Hospital Fertility Center. Linear and quantile regression were used to determine the association of soy foods and isoflavones intake with semen quality parameters while adjusting for personal characteristics.

RESULTS: There was an inverse association between soy food intake and sperm concentration that remained significant after accounting for age, abstinence time, body mass index, caffeine and alcohol intake and smoking. In the multivariate-adjusted analyses, men in the highest category of soy food intake had 41 million sperm/ml less than men who did not consume soy foods (95% confidence interval = –74, –8; P, trend = 0.02). Results for individual soy isoflavones were similar to the results for soy foods and were strongest for glycitein, but did not reach statistical significance. The inverse relation between soy food intake and sperm concentration was more pronounced in the high end of the distribution (90th and 75th percentile) and among overweight or obese men. Soy food and soy isoflavone intake were unrelated to sperm motility, sperm morphology or ejaculate volume.

CONCLUSIONS: These data suggest that higher intake of soy foods and soy isoflavones is associated with lower sperm concentration.

Key words: soy/isoflavones/semen analysis/sperm concentration/infertility

Submitted on March 3, 2008; resubmitted on April 18, 2008; accepted on April 28, 2008.

この記事へのコメント

この記事へのトラックバック