For decades, various studies have found worldwide declines in sperm quality among healthy men. How, if at all, does diet influence sperm quality? To answer this question, scientists in Sweden conducted a small research study that was published in PLOS Biology.
Researchers at Linköping University examined 15 healthy young men and their sperm for two weeks. The study looked at sperm quality at the start of the study, after the first week of eating a healthy diet, and after the second week, which included large amounts of sugar.
Healthy diet intervention
During the first week, participants received healthy meals with an energy intake corresponding to their estimated total energy expenditure, or the amount of calories burned in a day adjusted to the amount of activity.
The diet, provided by the research team, assumed the following energy distribution over meals: breakfast 25%, lunch 30%, dinner 30%, and snacks 15%. Participants were only permitted to drink water during the first week of the study.
Pour some sugar on me
The second week, participants received the same healthy diet as the first week, but with extra sugar in the form of candy and sweetened beverages added in. This combination resulted in an energy intake that corresponded to 150% of their estimated total energy expenditure. This averaged out to be about 375 grams of sugar each day.
At the beginning of the study, one third of the participants had low sperm motility, the ability of sperm to move properly through the female reproductive tract to reach the egg. Motility is one of many factors that influence sperm quality. The researchers pointed out that they were surprised that the sperm motility of all the participants became normal over the course of the study, adding that the most pronounced effect was already apparent after the first week.
Changes apparent in just two weeks
“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 head researcher Anita Öst.
"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.”
The researchers also found that the small RNA fragments, which contribute to cell growth and are linked to sperm motility, also changed.
The researchers continue to study whether there is a link between male fertility and the RNA fragments in sperm. They will also investigate if the RNA code can be used for new diagnostic methods to measure sperm quality during in vitro fertilization.
The study pointed out that sperm quality can be harmed by a number of factors, such as obesity and type 2 diabetes.
December 26, 2019. https://doi.org/10.1371/journal.pbio.3000559
"Human sperm displays rapid responses to diet"
Authors: Nätt, D., et al.