Published 29 October 2021
The largest study to date on sweetened drinks and testicular function finds a link between consumption and sperm counts, although the authors are reluctant to extrapolate the link to male fertility.
A global decline in total sperm counts, especially among men in western countries, continues to spark doomsday predictions. The most striking warning came from a meta-analysis in 2017 which found a 50-60% worldwide fall over nearly four decades among men, with no evidence of any levelling-off.(1) Describing this as ‘the canary in the coalmine’ for male health, the authors predicted that the implications reached far beyond fertility and into scenarios of shortened lifespan and chronic disease.
Last year a group from Harvard University called these dramatic findings into question, for reasons (among others) that ‘declining sperm counts do not predict declining fertility’.(2) However, a degree of panic around male fertility has been building since the 1990s, with multiple studies over the years repeating the message that men are producing fewer sperm and of poorer quality.
From chemicals in packaging to tight trousers, this spiralling trend has been attributed to multiple factors. High sugar intake as part of unhealthy modern lifestyles is now another on the risk list, with several studies linking sugary drinks with testicular function. The latest study on sugar-sweetened beverages (SSBs) – and the largest to date – concludes that a high daily intake of 220 ml on average of these drinks may adversely affect sperm count and concentration, as well as other parameters.(3)
Their aim, said the study authors, was to improve knowledge in an area where previous attempts at clarity had failed, in part because of the differing contents and composition of drinks on sale. They analysed data on 2935 men with a median age of 19 years who (between 2008 and 2017) underwent a compulsory medical fitness examination for military service in Denmark.
A questionnaire was used to ascertain the frequency of consumption of SSBs, artificially sweetened beverages (ASBs), fruit juices and energy-drinks among the young men known to be non-azoospermic. Sugar-sweetened fruit-flavoured and cola beverages were among the refreshments consumed along with the energy drink Red Bull. Testicular function was assessed through conventional semen quality analysis, testicular volume with ultrasound, and concentrations of reproductive hormones (SHBG, serum inhibin-B and inhibin-B/FSH).
Participants were asked how much water (including mineral and soda) they drank, and the authors also estimated the effect of substituting water for any beverage in the study. Frequency of intake was measured over the previous week (soft drinks, energy drinks) and past three months (water, fruit juice, fruit-flavoured beverages).
The results showed that average BMI was 22, and the proportion of beverage non-consumption among participants was 12% for SSBs, 64% ASBs, 14% fruit juice, and 70% energy drinks. Those who drank the highest volume of SSBs (average daily serving 220 ml) had a 13.2 million/ml lower average sperm concentration and 28 million lower total sperm count than non-consumers. The pattern was similar with serum inhibin-B/FSH ratios.
In addition, men who increased their SSB intake by one 220 ml serving a day instead of drinking water had a 3.4 million/ml lower average sperm concentration and 7 pg/ml lower inhibin-B concentration. Consuming an extra serving of ASBs (average daily serving 180 ml) in place of water was associated with lower concentration of total sperm motility and higher estradiol and LH concentrations.
Similar trends were observed among men who drank the highest amounts of ASBs: total sperm motility, progressive sperm motility and serum SHBG concentration were all lower on average than found in non-consumers. However, those who consumed the most energy drinks (average daily serving 80 ml) had higher percentages of morphologically normal sperm and concentrations of E2 and LH than found with non-energy drink consumers.
No association was found between fruit juice and water intake with any of the testicular function parameters examined.
The authors did adjust for more than a dozen confounders, such as BMI, physical activity levels, total energy intake and dietary patterns. But they acknowledge they could not measure lifestyle and behaviour, or other factors associated with testicular function in young men.
The relationship between ASB/energy drink intake with sperm motility was ‘unexpected’, said the authors, and establishing its clinical relevance ‘a challenge’, adding that their specific findings on a positive association with morphically normal sperm ‘should be treated with caution’.
So, does this research add weight to the male fertility apocalypse? It appears not. While semen parameters remain the cornerstones for clinical diagnosis, the authors say this study’s ability to predict the chance of pregnancy is limited. Thus, they cautiously add that any association between sugary drinks and lower semen quality ‘does not necessarily imply a decrease in fertility’.
What they do advise men to do is to replace SSBs with water in order to protect testicular function. A simple but practical solution for alleviating a potential fertility crisis.
1. Levine H, Jorgensen N, Martino-Andrade A, et al. Temporal trends in sperm count: a systematic review and meta-regression analysis. Human Reprod Update 2017; 23; 646–659; doi:10.1093/humupd/dmx022
2. Boulicault M, Perret M, Galka J, et al. The future of sperm: a biovariability framework for understanding global sperm count trends. Human Fert 2021; https://doi.org/10.1080/14647273.2021.1917778
3. Nassan F, Priskorn L, Salas-Huetos A, et al. Association between intake of soft drinks and testicular function in young men. Human Reprod 2021; doi:10.1093/humrep/deab179
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