may boost a man's sperm count, and therefore may improve a couple's chances of
conception, according to a new study.
In particular, men who lift
weights or spend time working or exercising outdoors tended to have a
higher-than-average sperm concentration in their semen, said study co-author
Audrey Gaskins, a doctoral student at the Harvard School of Public Health.
"Men engaging in
exercise for seven hours or more per week, essentially one hour a day, had 48%
higher concentrations than men who were engaging in less than one hour per
week," Gaskins said.
Moderate to vigorous activity
The study will be presented at the joint meeting of the International Federation of Fertility
Societies and the American Society for Reproductive Medicine, held in Boston.
Meanwhile, two other
studies being released at the meeting found that neither coffee nor alcohol
affects a man's ability to conceive, contradicting concerns raised by earlier
"Even though caffeine
and alcohol are generally considered a risk factor for decreased fertility, we
saw no evidence of that," said co-author Dr Jorge Chavarro, an assistant
professor of nutrition and epidemiology at the Harvard School of Public Health.
The exercise study focused
on the male partners of couples who sought treatment at the Massachusetts
General Hospital Fertility Centre between 2006 and 2012. Ultimately, 137 men
provided semen samples and filled out questionnaires regarding their regular
levels of physical activity.
"When we looked
overall, we found that men who engaged in levels of moderate to vigorous
activity had higher levels of sperm concentration," Gaskins said.
Further, the researchers
found that particular types of pursuits boosted sperm counts more than others.
"Outdoor activities and weightlifting seemed to be driving the association
between moderate to vigorous activity and sperm concentration," Gaskins
Men who spent more than an
hour and a half each week engaging in physical activity outdoors had a 42% higher
sperm concentration than those who spent no time outdoors, she said.
Increased testosterone levels
Weightlifters who spent two
or more hours a week pumping iron had a 25% increase in sperm count compared to
men who did not lift weights.
been shown to increase testosterone levels and improve insulin
sensitivity," Gaskins said. "Both of those have been related to
higher sperm concentrations."
Gaskins speculated that
outdoor exposure to sunlight might boost fertility by increasing men's levels
of vitamin D.
The researchers found that
one form of outdoor exercise actually can decrease male fertility, however. Men
who rode a bicycle for more than an hour and a half each week had 34% lower
sperm concentrations than men who did not bike.
Pressure placed against the
scrotum by a bike seat or the increased scrotal temperatures caused by such
pressure are possible explanations for this decrease in fertility, Gaskins
The study did not find any
difference in the quality of sperm or how well it travelled in the body related
Although the studies found
associations between exercise levels and sperm concentration, it did not prove
a cause-and-effect relationship.
Two other studies assessing
male fertility looked at the potential impact of alcohol or caffeine.
One study reviewed the
alcohol and caffeine intake of 166 male infertility patients, and found no link
with the men's sperm counts.
"We found that neither
alcohol nor caffeine affected semen quality, which serves as a proxy for male
fertility potential," Chavarro said.
A second study
A second study by French
researchers also looked at caffeine intake, but focused on the possibility that
caffeine could do harm to the quality of sperm as well as the quantity.
The study, which involved
nearly 4 500 men, reviewed semen volume and sperm counts, and performed genetic
analysis to see if caffeine caused damage to sperm DNA.
The researchers reported
that caffeine intake overall did not have a detrimental effect on semen. In
particular, caffeine did not seem to cause any significant damage to the DNA
carried by the sperm.
Until now, research into
the effects of caffeine and alcohol on male fertility has been very mixed,
"There have been many
papers suggesting that alcohol and caffeine may be deleterious to
fertility," he said. "But there have been a few papers that say
caffeine might help sperm motility, and helps sperm move faster with improved
Because the new research was
presented at a medical meeting, all data and conclusions should be viewed as
preliminary until published in a peer-reviewed journal.
For more about male
infertility, visit the US
National Library of Medicine.