Phytoestrogen intake and other dietary risk factors for low motile sperm count and poor sperm morphology.

BACKGROUND: Few potentially modifiable risk factors of male infertility have been identified, and while different diets and food groups have been associated with male infertility, evidence linking dietary factors including phytoestrogens and semen quality is limited and contradictory. OBJECTIVES: To study the associations between phytoestrogen intake and other dietary factors and semen quality. MATERIALS AND METHODS: A case-referent study was undertaken of the male partners, of couples attempting conception with unprotected intercourse for 12 months or more without success, recruited from 14 UK assisted reproduction clinics. A total of 1907 participants completed occupational, lifestyle and dietary questionnaires before semen quality (concentration, motility and morphology) were assessed. Food intake was estimated by a 65-item food frequency questionnaire (FFQ) covering the 12 months prior to recruitment. Analyses of dietary risk factors for low motile sperm concentration (MSC: <4.8 × 106 /mL) and poor sperm morphology (PM: <4% normal morphology) used unconditional logistic regression, accounting for clustering of subjects within the clinics, first without, and then with, adjustment for confounders associated with that outcome. RESULTS: High consumption of daidzein (≥13.74 µg/d), a phytoestrogen found in soy products, was a protective factor for MSC with an odds ratio (95%CI) of 0.58 (0.42-0.82) after adjustment for clustering and potential confounding. Dietary risk factors for PM after similar adjustment showed that drinking whole milk (OR 0.67, 95%CI 0.47-0.96) and eating red meat were protective with an OR 0.67 (0.46-0.99) for eating red meat >3 times/wk. DISCUSSION: In this case-referent study of men attending an infertility clinic for fertility diagnosis, we have identified that low MSC is inversely associated with daidzein intake. In contrast, daidzein intake was not associated with PM but eating red milk and drinking whole milk were protective. CONCLUSIONS: Dietary factors associated with semen quality were identified, suggesting that male fertility might be improved by dietary changes.

Occupation exposures and sperm morphology: a case-referent analysis of a multi-centre study.

OBJECTIVE: We examined occupational exposures and sperm morphology to establish whether exposures implicated differed from those affecting motile sperm concentration. METHODS: Computer aided sperm morphometric assessment was undertaken on morphology slides obtained as part of a multi-centre study in 1999-2002 of occupational factors in male infertility. Men attending 14 fertility clinics across the UK were recruited and gave a semen sample. Before results of the semen analysis were known, the men completed detailed questionnaires about their employment and lifestyle. Occupational exposures were assessed by occupational hygienists. Data were analysed using an unmatched case-referent design, allowing for clustering and for confounders. Three case definitions were used: poor morphology (normal morphology <4%), low motile sperm count (MSC) (<4.8×10(6)) and either condition. RESULTS: Morphology results were available for 1861/2011 men employed at the time of recruitment. Of these 1861, 296 (15.9%) had poor morphology; of the 2011with sperm count, 453 (22.5%) had low MSC; 654/1981 (33.0%) had either condition. Poor morphology, adjusted for confounding, was related to self-reported lifetime exposure to lead (OR=1.33; 95% CI 1.00 to 1.75). Low MSC was also related to self-reported lead and to hygienist-assessed glycol ether exposure. Self-reported use of paint stripper (OR=1.47; 95% CI 1.07 to 2.03) and lead, but not glycol ether, were significantly related to the combined case definition. CONCLUSIONS: While this study did not identify any occupational exposure uniquely related to sperm morphology, the capacity of the study to detect risk was increased by including morphology with sperm concentration and motility.