Study question: What are the associations between the dietary intake of antioxidant nutrients and semen parameters in young men?
Summary answer: Our study suggests that some sperm parameters are sensitive to dietary intake of antioxidant nutrients.
What is known already: A few reports have suggested that some dietary factors might be related to semen quality. However, the relationship between the intake of antioxidant nutrients and semen quality in young men remains unexplored.
Study design, size, duration: In this cross-sectional study, 215 young men were included between October 2010 and November 2011.
Participants/materials, setting, methods: Healthy university students with complete dietary and semen quality data were analyzed. Dietary intake was recorded using a validated food frequency questionnaire. The associations between the energy-adjusted nutrient intake of antioxidants in quartiles and the semen volume, sperm concentration, sperm motility, sperm morphology, total sperm count and total motile sperm count were assessed using multivariate linear regression.
Main results and the role of chance: Out of 240 students who contacted us, 223 (92.9%) were eligible to participate in this study, and 215 attended the clinical appointment. In the multivariate adjusted linear regression models, there was a positive association between dietary intakes of cryptoxanthin (P(trend) = 0.03), vitamin C (P(trend) = 0.04), lycopene (P(trend) = 0.03) and β-carotene (P(trend) = 0.04) and total motile sperm count. The semen volume increased with higher intakes of vitamin C (P(trend) = 0.04).
Limitations, reasons for caution: Only one sample of semen was taken for each subject. However, there are indications that one semen sample may be sufficient to characterize the semen quality of the individuals in epidemiological studies. Bias due to measurement errors may also occur since there is no perfect method to assess diet. However, any bias due to measurement error would be non-differential and would reduce, not increase, the strength of the associations. Although selection bias in cross-sectional studies might not always be ruled out, our subjects were university student volunteers who were rewarded for their participation and the study was not advertised as a fertility study.
Wider implications of the findings: Previous articles in this area have focused mainly on men attending fertility clinics, thus our study brings generalizability to young men of the general population with unknown or untested fertility. Some of our results are in agreement with the previously reported papers.