In a new study, researchers found that sperm are influenced by diet, and the effects arise rapidly.
The sperm motility of men who followed a diet high in sugar was improved fast.
The finding gives new insight into the function of sperm, and may in the long term contribute to new diagnostic methods to measure sperm quality.
The research was conducted by a team at Linköping University.
Sperm quality can be harmed by several environmental and lifestyle factors, of which obesity and related diseases, such as type 2 diabetes, are well-known risk factors for poor sperm quality.
The research group that carried out the new study is interested in epigenetic phenomena, which involve physical properties or levels of gene expression changing, even when the genetic material, the DNA sequence, is not changed.
In certain cases such epigenetic changes can lead to properties being transferred from a parent to offspring via the sperm or the egg.
In a previous study, the scientists showed that male fruit flies that had consumed excess sugar shortly before mating more often produced offspring who became overweight.
Similar studies on mice have suggested that small fragments of RNA known as tsRNA play a role in these epigenetic phenomena that appear in the next generation.
These RNA fragments are present in unusually large amounts in the sperm of many species, including humans, fruit flies, and mice. So far, their function has not been examined in detail.
Scientists have speculated that the RNA fragments in sperm may be involved in epigenetic phenomena, but it is too early to say whether this is the case in humans.
The new study was initiated by the researchers to investigate whether high consumption of sugar affects the RNA fragments in human sperm.
In the study, 15 normal, non-smoking young men, who followed a diet rich in sugar.
At the beginning of the study, one-third of the participants had low sperm motility.
Motility is one of several factors that influence sperm quality, and the fraction of people with low sperm motility in the study corresponded to that in the general population.
The researchers were surprised to discover that the sperm motility of all participants became normal during the study.
The study shows that sperm motility can be changed in a short period, and seems to be closely coupled to diet.
The team says sugar may be a component of the basic healthy diet that has a positive effect on the sperm.
The researchers found that the small RNA fragments, which are linked to sperm motility, also changed.
They are now planning to continue the work and investigate whether there is a link between male fertility and the RNA fragments in sperm.
The lead author of the study is Anita Öst, senior lecturer in the Department of Clinical and Experimental Medicine at Linköping University.
The study is published in PLOS Biology.
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