London: If you want to preserve the quality of your sperm make sure you don't regularly eat a diet rich in sugar, says a new research adding that sperm are influenced by diet, and the effects arise rapidly.
The study, published in the journal PLOS Biology, gives new insight into the function of sperm and may, in the long term, contribute to new diagnostic methods to measure sperm quality.
"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 study lead author Anita Ost from the Linkoping University in Sweden.
According to the researchers, 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 researchers showed that male fruit flies which 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 significant 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.
This study was initiated by the researchers to investigate whether a high consumption of sugar affects the RNA fragments in human sperm.
The research examined 15 normal, non-smoking young men, who followed a diet in which they were given all food from the scientists for two weeks.
The diet was based on the Nordic Nutrition Recommendations for healthy eating with one exception: during the second week the researchers added sugar, corresponding to around 3.5 litres of fizzy drinks, or 450 grammes of confectionery, every day.
The sperm quality and other indicators of the participants' health were investigated at the start of the study, after the first week (during which they ate a healthy diet), and after the second week (when the participants had additionally consumed large amounts of 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. This has important clinical implications," said Anita Ost.
The researchers also found that the small RNA fragments, which are linked to sperm motility, also changed.