Trans fatty acid intake is inversely related to total sperm count in young healthy men

STUDY QUESTION: Is intake of fatty acids related to semen quality among young men? SUMMARY ANSWER: The intake of trans fatty acids is inversely related to total sperm count in healthy young men. WHAT IS KNOWN ALREADY: Spain has seen an increase in the proportion of calories consumed as fat over the same period that a downward trend in semen quality has been observed. In addition, rodent models suggest that trans fat intake may severely affect testicular function. STUDY DESIGN, SIZE, DURATION: Cross-sectional study of 209 men recruited between October 2010 and November 2011. PARTICIPANTS/MATERIALS, setting, methods: A group of 209 healthy young university students 18-23 years of age provided a semen sample and completed a previously validated food frequency questionnaire. The association between intake of fatty acids with semen quality parameters (sperm concentration, motility, morphology and total count) was assessed using multivariate linear regression. MAIN RESULTS AND THE ROLE OF THE CHANCE: Trans fatty acid intake was inversely related to total sperm count after adjusting for potential confounders (P, trend = 0.03). The multivariate adjusted mean (95% confidence interval) total sperm count in increasing quartiles of trans fat intake was 144 (110-190), 113 (87-148), 100 (18-130) and 89 (69-117). There also was an inverse association between cholesterol intake and ejaculate volume (P, trend = 0.04). No other statistically significant relations were observed. LIMITATIONS, REASONS FOR CAUTION: The cross-sectional design of the study limits causal inference, we cannot exclude the possibility of unmeasured confounding and there was insufficient statistical power to identify modest associations. WIDER IMPLICATIONS OF THE FINDINGS: The results of this study, together with previous experimental work in rodents and biomarker studies among infertility patients, suggest that intake of trans fatty acids may be related to lower semen quality. Although the data provide further evidence that diet is a modifiable factor that could impact male fertility, it is not known whether the observed differences in sperm count translate into differences in fertility.