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HomeHuman Reproductionindex/list_12208_2Association Between Intake of Soft Drinks and Testicular Function in Young Men

Association Between Intake of Soft Drinks and Testicular Function in Young Men

Abstract and Introduction

Abstract

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.

Introduction

One in six couples trying to conceive experience infertility—the inability to conceive after 12 months of unprotected sexual intercourse (Louis et al., 2013; Thoma et al., 2013), with major financial and psychological implications (Macaluso et al., 2010). Male factors are implicated in as many as 58% of such cases, including one third of cases attributed to a combination of male and female factors (Thonneau et al., 1991). Genetics contribute only to 10–15% of male infertility (Dohle et al., 2002), highlighting the growing evidence that testicular function, including spermatogenesis, is sensitive and responsive to environmental exposures such as environmental chemicals, air pollution and diet (Minguez-Alarcon et al., 2018).

The intake of energy-dense foods, added sugars and sugar-sweetened beverages (SSBs) has increased worldwide (Malik et al., 2010), and a large part of the Danish population exceeds the national dietary recommendation for intake of added sugars (Pedersen et al., 2010). While numerous adverse health effects of SSB intake have been documented, including higher rates of obesity, diabetes, and heart disease (Malik et al., 2010), whether SSBs can also negatively impact reproductive function generally and male reproductive function specifically is less clear. Three previous studies have examined the association between SSB intake and testicular function (Jensen et al., 2010; Chiu et al., 2014; Yang et al., 2015). Although they reported inverse associations with one or more semen parameters, the associations were different across studies. An American study (Chiu et al., 2014) found an inverse relation with progressive sperm motility and a Chinese study (Yang et al., 2015) reported lower semen volume with increased SSB intake. Also, in a previous report focused on intake of caffeinated beverages, we reported an inverse association of intake of cola soft drinks, i.e. SSB, but not other caffeine-containing drinks, with sperm concentration and total sperm count (Jensen et al., 2010). In addition, a study of couples attempting conception in North America, found that men’s intake of SSBs was associated with longer time to pregnancy, independent of their partners’ SSB intake (Hatch et al., 2018).

Although the harmful health effects of SSB have received substantial attention in recent years, the health effects of other beverages that could be used to substitute SSB intake, such as artificially sweetened beverages (ASB) and fruit juices, have received less attention. However, nutritionally, some fruit juices are not very different form SSB. Also, if health effects of SSB can be partially attributed to contamination with environmental chemicals, such as plasticizers used to cover the inner lining of cans, rather than their nutritional properties, similar associations could be expected with intake of ASBs. Moreover, in the last decade, many energy drinks have become widely available, some of which have sugar contents equivalent to SSBs but are substantially different in other regards such as their caffeine content. It is, therefore, important to characterize the health risk profile of beverages beyond that of SSBs. To address this important knowledge gap as it relates to male reproductive health, we examined the association of intakes of SSB, ASB, energy-drinks, and fruit juices among young Danish men with markers of testicular function including semen quality, testicular volume, and serum reproductive hormones. We hypothesized that higher intake of SSBs, but not other soft drinks (ASB, fruit juice, and energy drinks), would be associated with lower testicular function.

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