Diet has rapid effects on sperm quality

Diet can influence sperm quality after just a few weeks according to a small study from Sweden's Linkoping University. The study reinforces the link between nutrition and male reproduction and could have important implications for those undergoing fertility treatment.

In the study, 15 non-smoking men aged 20-27 followed a specific diet for two weeks. In the first week they ate a healthy diet as recommended by the Nordic Nutrition Recommendations. During the second week, the men ate an extra 375g of sugar per day, which is equivalent to about 3.5 litres of sugary drinks.

Sperm motility, which is linked to sperm quality, was measured at the start of the study, after one week and after two weeks. At the beginning of the study, a third of the men had low sperm motility but during the course of the study the researchers found that the sperm motility of all participants became normal.

'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', says Anita Öst, senior lecturer in the Department of Clinical and Experimental Medicine at Linköping University, and head of the study.

The research team were interested in looking at epigenetics, a biological phenomenon where environmental factors such as diet can affect which genes are switched on even when there is no change to the genetic code itself. These changes can be passed down to future generations. In a previous study the scientists have shown that male fruit flies who eat a high sugar diet before mating tend to have more overweight offspring.

Similar studies on mice have suggested that tsRNAs, small fragments of RNA, play a role in passing epigenetic effects down to future generations but how they do this and whether this is the case in humans as well is not yet known, although tsRNA fragments have been found in very high levels in the sperm of mice, humans and fruit flies. The team from Linkoping University measured tsRNAs in the sperm to see if they are linked to sugar consumption and they discovered that tsRNA levels were increased in some of the men after they had eaten a high sugar diet for a week.

Although the scientists measured sperm motility they did not look at whether diet has any effect on male fertility but this will be addressed in future research. The team also plans to explore whether the RNA fragments could be used as a new measure of sperm quality during assisted reproduction.