In a study of men with fertility problems, researchers found that daily ejaculation for a week cut the amount of DNA damage seen in sperm samples.
"All that we knew was that intercourse on the day of ovulation offered the highest chance of pregnancy, but we did not know what was the best advice for the period leading up to ovulation or egg retrieval for IVF," Dr David Greening, an obstetrician and gynaecologist with sub specialist training in reproductive endocrinology and infertility at Sydney IVF, Wollongong, Australia, said.
"I thought that frequent ejaculation might be a physiological mechanism to improve sperm DNA damage, while maintaining semen levels within the normal, fertile range," he added.
To investigate this hypothesis, Greening studied 118 men who had higher than normal sperm DNA damage as indicated by a DNA Fragmentation Index (DFI).
Men who had a more than 15 percent of their sperm damaged were eligible for the trial. At Sydney IVF, sperm DNA damage is defined as less than 15 percent DFI for excellent quality sperm, 15-24 percent DFI for good, 25-29 percent DFI for fair and more than 29 percent DFI for poor quality; but other laboratories can have slightly different ranges.
The men were instructed to ejaculate daily for seven days, and no other treatment or lifestyle changes were suggested. Before they started, levels of DNA damage ranged between 15 percent and 98 percent DFI, with an average 34 percent DFI when measured after three days'' abstinence.
When the men''s sperm was re-assessed on the seventh day, Greening found that 81 percent men had an average 12 percent decrease in their sperm DNA damage, while 19 percent men and an average increase in damage of nearly 10 percent. The average for the whole group dropped to 26 percent DFI.
"Although the mean average was 26 percent which is in the ''fair'' range for sperm quality, this included 18 percent of men whose sperm DNA damage increased as well as those whose DNA damage decreased," Greening said.
"Amongst the men whose damage decreased, their average dropped by 12 percent to just under 23 percent DFI, which puts them in the ''good'' range. Also, more men moved into the ''good'' range and out of the ''poor'' or ''fair'' range. These changes were substantial and statistically highly significant.
"In addition, we found that although frequent ejaculation decreased semen volume and sperm concentrations, it did not compromise sperm motility and, in fact, this rose slightly but significantly.
"Further research is required to see whether the improvement in these men''s sperm quality translates into better pregnancy rates, but other, previous studies have shown the relationship between sperm DNA damage and pregnancy rates," he added.
Greening said he thought the reason why sperm quality improved with frequent ejaculation was because the sperm had a shorter exposure in the testicular ducts and epididymis to reactive oxygen species - very small molecules, high levels of which can damage cells.
"The remainder of the men who had an increase in DFI might have a different explanation for their sperm DNA damage," he said.
The study has been presented at the 25th annual meeting of the European Society of Human Reproduction and Embryology in Amsterdam.