While it's known that environmental factors influence the quality of sperm over time, researchers have found that diet can have a rapid impact on sperm. The study was conducted with a small group of fifteen healthy volunteers that were given a regular diet followed by one high in sugar. The findings, by scientists at Linköping University, have been reported in PLOS Biology.
"We see that diet influences the motility of the sperm, and we can link the changes to specific molecules in them. Our study has revealed rapid effects that are noticeable after one to two weeks," said the research leader Anita Öst, senior lecturer in the Department of Clinical and Experimental Medicine at Linköping University.
Previous work has shown that in a fruit fly model, males that were given more sugar ended up producing more offspring than males not given sugar. This phenomenon may be affected by molecules called tsRNA (tRNA-derived small RNA). Once thought of as a potential remnant of degraded tRNA, tsRNAs are now thought to play many important regulatory roles in various physiological processes. They are also known to affect different aspects of gene expression, including protein production and epigenetic tags, which are chemical modifiers that influence gene expression (epigenetics is discussed in the video). Sperm carries high levels of tsRNA.
In this work, for two weeks fifteen healthy young men followed a diet given to them by the researchers that was based on nutritional recommendations, except that in the second week they got extra sugar. During the week of added sugar, they either consumed about 3.5 liters of soda or 450 grams of sweets a day. Sperm quality was assessed during each week.
Around a third of the study participants had sperm with low motility at the start of the research. This corresponds to the average level of low motility in sperm in the general population. During the study, all of the volunteers reached normal sperm motility levels, surprising the researchers.
"The study shows that sperm motility can be changed in a short period, and seems to be closely coupled to diet. This has important clinical implications. But we can't say whether it was the sugar that caused the effect, since it may be a component of the basic healthy diet that has a positive effect on the sperm," said Öst.
The investigators also determined that the small fragments of RNA had changed. They want to learn more about how these fragments are connected to male fertility, and whether they may aid in the development of diagnostic tools that can assess sperm quality.