全脂肪乳製品を多く取ると精子の形態異常が増え、精子の運動能力が落ちる

全脂肪乳製品、精子の質下げる

不妊治療に乳製品の摂取制限が有効の可能性

全脂肪乳製品を多く取る男性は、精子の形態異常が増えるほか、精子の運動能力が落ちる傾向にあることが分かった。Human Reproduction誌8月号に掲載されている。

米国の研究グループは、乳製品の摂取と精子の質低下が関係するのではないかとの仮説を設定。2009年から2010年、189人の男性を対象に、食品の摂取頻度、精子の数、精子濃度、運動率、奇形率、射精量を調べた。年齢、禁欲期間、人種、喫煙などの条件により補正し回帰分析を実施。

乳製品の摂取量と精子の形態異常とは、逆相関にあると見いだした。全脂肪乳製品の摂取量で上位半分の群は、下位半分の群よりも正常形態の精子の割合は3.2％少なかった。低脂肪乳でも同様な傾向は見られたが、1.3％少ないにとどまった。全脂肪乳製品の摂取量増加は、精子の運動能力低下にも関係していた。

研究グループは、不妊治療において乳製品の摂取制限が有効である可能性を指摘している。

Dairy food intake in relation to semen quality and reproductive hormone levels among physically active young men

• M. Afeiche,, P.L. Williams, J. Mendiola, A.J. Gaskins, N. Jørgensen,S.H. Swan and J.E. Chavarro

Author Affiliations

• ¹Department of Nutrition, Harvard School of Public Health, Boston, MA 02115, USA

• ²Department of Biostatistics, Harvard School of Public Health, Boston, MA 02115, USA

• ³Division of Preventive Medicine and Public Health, University of Murcia School of Medicine, Murcia 30003, Spain

• ⁴Department of Epidemiology, Harvard School of Public Health, Boston, MA 02115, USA

• ⁵University Department of Growth and Reproduction, University of Copenhagen, Rigshospitalet, Copenhagen DK-2100, Denmark

• ⁶Department of Obstetrics and Gynecology, School of Medicine, University of Rochester, Rochester, NY 14642, USA

• ⁷Department of Preventive Medicine, Mount Sinai School of Medicine, New York, NY 10029, USA

• ⁸Channing Division of Network Medicine, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115, USA

• • Received January 14, 2013.

  • Revision received March 27, 2013.

  • Accepted April 4, 2013.

Abstract

STUDY QUESTION

Is increased consumption of dairy foods associated with lower semen quality?

SUMMARY ANSWER

We found that intake of full-fat dairy was inversely related to sperm motility and morphology. These associations were driven primarily by intake of cheese and were independent of overall dietary patterns.

WHAT IS KNOWN ALREADY

It has been suggested that environmental estrogens could be responsible for the putative secular decline in sperm counts. Dairy foods contain large amounts of estrogens. While some studies have suggested dairy as a possible contributing factor for decreased semen quality, this finding has not been consistent across studies.

STUDY DESIGN, SIZE, DURATION

The Rochester Young Men's Study (n= 189) was a cross-sectional study conducted between 2009 and 2010 at the University of Rochester.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Men aged 18–22 years were included in this analysis. Diet was assessed via food frequency questionnaire. Linear regression was used to analyze the relation between dairy intake and conventional semen quality parameters (total sperm count, sperm concentration, progressive motility, morphology and ejaculate volume) adjusting for age, abstinence time, race, smoking status, body mass index, recruitment period, moderate-to-intense exercise, TV watching and total calorie intake.

MAIN RESULTS AND THE ROLE OF CHANCE

Total dairy food intake was inversely related to sperm morphology (P-trend = 0.004). This association was mostly driven by intake of full-fat dairy foods. The adjusted difference (95% confidence interval) in normal sperm morphology percent was −3.2% (−4.5 to −1.8) between men in the upper half and those in the lower half of full-fat dairy intake (P < 0.0001), while the equivalent contrast for low-fat dairy intake was less pronounced [−1.3% (−2.7 to −0.07; P= 0.06)]. Full-fat dairy intake was also associated with significantly lower percent progressively motile sperm (P= 0.05).

LIMITATIONS, REASONS FOR CAUTION

As it was a cross-sectional study, causal inference is limited.

WIDER IMPLICATIONS OF THE FINDINGS

Further research is needed to prove a causal link between a high consumption of full-fat dairy foods and detrimental effects on semen quality. If verified our findings would mean that intake of full-fat dairy foods should be considered in attempts to explain secular trends in semen quality and that men trying to have children should restrict their intake.

STUDY FUNDING/COMPETING INTEREST(S)

European Union Seventh Framework Program (Environment), ‘Developmental Effects of Environment on Reproductive Health’ (DEER) grant 212844. Grant P30 DK046200 and Ruth L. Kirschstein National Research Service Award T32 DK007703-16 from the National Institutes of Health. None of the authors has any conflicts of interest to declare.