'Daily sex for week boosts conception chance'
Daily sex keeps a man's sperm spry and is recommended for couples wanting a baby, research has shown.
Having regular sex clears sperm from the testicles and prevents the natural build-up of DNA damage, scientists have found.
The Australian experts said would-be fathers should have sex once a day for a week before their partner is ready to conceive.
Overdoing the advice and having sex more often risked the man's sperm count falling too far.
Fertility doctors disagree about whether or not men should refrain from sex for a few days before their partner ovulates.
Men undergoing in-vitro fertilisation (IVF) treatment are routinely told to stop having sex.
The reason for abstinence is that frequent sex causes a drop in sperm count - the number of sperm produced in each ejaculation.
But the new research suggests that, rather than reducing the chances of conception, daily sex can increase it.
DNA damage lessened in the sperm of men having daily sex as "old" sperm was cleared away and replaced by fresh cells.
Daily sex also seemed to make the sperm more active, or motile - which is known to improve fertility.
Damage to sperm DNA is mainly due to destructive oxygen molecules generated naturally by cells in the body.
Dr David Greening, from the Sydney IVF clinic in Wollongong, said: "Keeping the river flowing means the sperm doesn't hang around so long and become damaged. There's less time for vandalism.
"We advise couples to try to work out when the woman's ovulating and have lots of sex."
Dr Greening's team studied 118 men who had higher than normal DNA damage to their sperm, as assessed by the DNA Fragmentation Index (DFI).
Men who had more than 15% of their sperm damaged were eligible for the trial.
At the Sydney clinic, a DFI of less than 15% is defined as "excellent quality" sperm, while 15% to 24% is rated as "good", 25% to 29% "fair" and more than 29% "poor".
Levels of DNA damage among the study participants ranged between 15% and 98% at the start of the trial, averaging at 34%.
The men were instructed to ejaculate daily for seven days and recommended no other treatments or lifestyle changes.
On the seventh day, 96 men (81%) were found to have experienced an average 12% decrease in sperm DNA damage.
A minority of 22 men, or 19%, suffered an almost 10% increase in damage. However, average DFI for the whole group had dropped to 26%.
"Although the mean average was 26%, which is in the 'fair' range for sperm quality, this included 18% of men whose sperm DNA increased as well as those whose DNA damage decreased," said Dr Greening.
"Amongst the men whose damage decreased, their average dropped by 12% to just under 23% 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."
The men's average sperm counts went down from 180 million to 70 million after a week of daily sex.
"This is still within the acceptable range," said Dr Greening. "They actually swam better, and motility is really important."
Dr Greening presented the findings today at the annual meeting of the European Society of Human Reproduction and Embryology (Eshre) in Amsterdam.
He said further research was needed to see if improving sperm quality by having daily sex led to better pregnancy rates. Previous research suggested that it should.
The ideal number of days having sex was more or less than seven, said the researchers, but a week appeared "manageable and favourable".
Dr Greening said sperm count was likely to "plummet" if enthusiastic couples had sex three times a day.
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