Association between intake of soft drinks and testicular function in young men

STUDY QUESTION: Is intake of sugar-sweetened beverages (SSB) or artificially sweetened beverages (ASB) associated with testicular function in young men? SUMMARY ANSWER: Among young men unaware of their semen quality and reproductive hormone levels, intake of SSBs was associated with lower sperm concentration, lower total sperm count, and a lower ratio of serum inhibin-B/FSH. WHAT IS KNOWN ALREADY: SSBs may adversely impact testicular function, but results are not consistent across studies. Moreover, the associations of ASB, energy-drinks or fruit juices with testicular function are unclear. STUDY DESIGN, SIZE, DURATION: Young healthy men and unselected for fertility status men enrolled in a cross-sectional study between 2008 and 2017. PARTICIPANTS/MATERIALS, SETTING, METHODS: A total of 2935 young (median age: 19 years) men enrolled in the study. Intake of SSBs, ASBs, fruit juices, and energy-drinks was assessed with a validated food frequency questionnaire. Testicular function was assessed through conventional semen quality parameters (semen volume, sperm concentration, total count, motility and morphology), testicular volume assessed with ultrasound, and serum reproductive hormone concentrations (total testosterone, free testosterone, E2, inhibin-B, LH, FSH, sex hormone-binding globulin) were measured. MAIN RESULTS AND THE ROLE OF CHANCE: In multivariable-adjusted analyses, men in the highest category of SSB intake (median: 1.1 servings (∼220 ml)/day) had a 13.2 million/ml lower median sperm concentration (95% CI:-21.0,-5.5) than non-consumers. A similar pattern was observed with total sperm count (-28 million (95% CI:-48,-9)), serum inhibin-B (-12 pg/ml (95% CI:-21,-4)), and inhibin-B/FSH ratio (-9 (95% CI:-18, 0)). The adjusted median difference in sperm concentration and inhibin-B associated with increasing SSB intake by 1 serving (∼200ml)/day at the expense of water was-3.4 million sperm/ml (95% CI:-5.8,-1.0) and-7 pg/ml (95% CI:-11,-3), respectively. LIMITATIONS, REASONS FOR CAUTION: Inferring causality is limited owing to the cross-sectional design. We adjusted for a number of potential confounders but cannot exclude that unmeasured lifestyle and behavior associated with soft drink intake is associated with testicular function in these young men. WIDER IMPLICATIONS OF THE FINDINGS: In the largest study to date, intake of SSBs was associated with lower sperm concentration, total sperm count, and serum inhibin-B/FSH ratio, consistent with a direct suppressive effect of SSB intake on testicular function among otherwise healthy men, potentially affecting fertility. However, the observed association between higher SSB intake and lower semen quality does not necessarily imply a decrease in fertility. STUDY FUNDING/COMPETING INTEREST(S): Supported by research from the Danish Council for Strategic Research (2101-08-0058), Independent Research Fund Denmark (8020-00218B), European Union (212844), the Kirsten and Freddy Johansen's Foundation (95-103-72087), the Research Fund of the Capital Region of Denmark (A6176), and the NIH (P30DK046200). The authors report no conflict of interest. TRIAL REGISTRATION NUMBER: N/A.