|
 Men who smoked more than two joints in their lifetime had a
significantly higher sperm concentration than those who had never
smoked marijuana: on average, 62.7 million sperm per milliliter of
semen versus 45.4 million/mL, Harvard researchers report in the
journal Human Reproduction.
The pattern was similar when researchers looked at the men's sperm
count. The count was higher, on average, in men who had ever smoked
marijuana, with no significant differences between those who had
only smoked weed in the past and those who were currently using it.
Observational studies like this one can't prove cause and effect -
and the lead author of the study was quick to warn against assuming
that marijuana actually caused the men in the study to have
healthier sperm.
"These findings do not mean that using marijuana will increase sperm
counts," lead author Feiby Nassan emphasized in an email. "These
results should not be interpreted as a reason to smoke marijuana."
Nassan's team studied 1,143 samples of semen obtained from 662 men
treated at the fertility center at Boston's Massachusetts General
Hospital between 2000 and 2017. They also studied hundreds of blood
samples from these men to determine levels of reproductive hormones.
The men were asked to report past and current marijuana use in a
questionnaire.
Weed smokers also performed better on another metric used to measure
fertility, the level of follicle stimulating hormone found in the
blood.
And they were also less likely to have poor sperm motility, which is
the ability of sperm to swim toward an egg.
However, when researchers studied sperm DNA integrity - which
assesses breakages in strands of sperm DNA - and levels of other
hormones, there were no significant differences between marijuana
smokers and non-smokers.
The study is "a real surprise," said reproductive endocrinologist
Dr. Channa Jayasena of Imperial College London, who was not involved
in the study. "We obviously need to be very careful about members of
the public jumping on to this."
[to top of second column] |
The findings are thought-provoking, he said. "This is a significant,
large study and it's been done to a high quality so the results
can't be ignored . . . It would be interesting to explore this
further."
Independent expert Dr. Michael Eisenberg, director of male
reproductive medicine and surgery at Stanford University in
California, believes it is too soon to make clinical recommendations
about marijuana use based on the study findings.
Cannabinoid receptors, which are cells that play a role in
marijuana's effect in the body, have also been shown to be important
in male fertility, he said, adding, "It is possible they are
activated by marijuana use to the benefit of (sperm development)."
"Given the wave of legalization and the common use, this is
certainly something that warrants further study," he said.
While marijuana use is illegal under U.S. federal law, several
states have passed laws allowing its recreational and medical use.
In the past, most research on the drug's effects on male fertility
have focused on substance abusers, linking cannabis-smoking to lower
sperm counts, the researchers note in their paper.
"Based on the preponderance of previous findings, we hypothesized
that marijuana smoking would be associated with worse semen quality
and lower serum testosterone," they said.
The results, however, proved contrary to this hypothesis, even after
the authors conducted sensitivity analyses and considered different
metrics of marijuana smoking.
Nassan points to two possible explanations. One is that low-level
marijuana use might benefit sperm production but the effect might be
reversed with heavier use. Equally possible, she said, is that men
with higher testosterone levels are more likely to engage in
risk-seeking behaviors, including marijuana smoking.
"The study is a great opportunity to spark interest in investigating
the health effects of marijuana," she said.
SOURCE: http://bit.ly/2Ns37yW Human Reproduction, online February 6,
2019.
[© 2019 Thomson Reuters. All rights
reserved.] Copyright 2019 Reuters. All rights reserved. This material may not be published,
broadcast, rewritten or redistributed.
Thompson Reuters is solely responsible for this content. |
