Mystique
Sun, Nov-16-03, 19:14
Now I understand why **sex tourism** from Japan to Hawaii is
so popular among Japanese men. D
Soy supplements cut sexual behavior in rats
17:45 14 November 03
NewScientist.com news service
Soy supplements can decrease normal sexual behaviour by as
much as 70 per cent, a study of female rats has shown.
The rats were given a commercially available supplement in
doses similar to those taken by women. The findings suggest a
possible negative side effect for the supplements, which are
becoming very popular among US women.
Isoflavones, the key compounds in soy, are estrogen-like
molecules. Soy supplements are touted as a natural alternative
to hormone replacement therapy and recent warnings of the
risks of HRT may boost the numbers of women turning to the
supplements.
The supplements do have other potential health benefits.
Women in the Far East, whose regular diet includes relatively
large amounts of soy, have much lower cancer rates than
Western women.
But some studies highlighted possible downsides. Soy
isoflavones have been show to interfere with estrogen function
in rats, decreasing some of the brain molecules involved in
social and sexual behaviour. And a specific isoflavone called
genistein prevents the tumour-fighting drug tamoxifen from
working in mice. The new study, showing that a soy isoflavone
has negative effects on sexual behavior in rats, joins these.
Encouraging behaviour
When female rats are on heat, they typically encourage nearby
male rats by changing their posture. Once a male rat has
approached, they change their position to be more receptive to
their mate.
Heather Patisaul and colleagues at Emory University in
Atlanta, Georgia, gave female rats small doses of soy
supplement. This produced blood levels of the isoflavone
similar those in women regularly taking the supplements.
The "encouraging behaviours" in the rats decreased by 70
per cent, while the "receptive behaviours" decreased by up
to 40 per cent.
The breast cancer drug tamoxifen, which opposes the function
of estrogen in some tissue, had a similar but smaller effect.
This, with evidence from other studies, leads Patisaul to
believe that the soy isoflavone is also acting as an
"estrogen opposer".
She adds that there is anecdotal evidence of decreased sex
drive in women taking tamoxifen, as well as problems with
vaginal dryness.
Confounding factor
Patisaul does not know if any such side effects have been
reported in women taking soy supplements. But she notes that
since most women take them for menopause, it would be
difficult for women to tell if changes in sex drive were due
to the pill or changing hormones.
"You would need to do a controlled clinical trial to sort it
out," she says. "But no one has asked these women about sexual
side effects. We need to look at all aspects of what [these
compounds] are doing."
Andrew Kaunitz, at the University of Florida in Jacksonville
and a researcher with the women's health initiative, agrees
that this should be looked into. "Interest in soy has
increased in recent years," he says.
The new study was presented on Wednesday at the Society for
Neurosciences meeting in New Orleans.
Emily Singer
so popular among Japanese men. D
Soy supplements cut sexual behavior in rats
17:45 14 November 03
NewScientist.com news service
Soy supplements can decrease normal sexual behaviour by as
much as 70 per cent, a study of female rats has shown.
The rats were given a commercially available supplement in
doses similar to those taken by women. The findings suggest a
possible negative side effect for the supplements, which are
becoming very popular among US women.
Isoflavones, the key compounds in soy, are estrogen-like
molecules. Soy supplements are touted as a natural alternative
to hormone replacement therapy and recent warnings of the
risks of HRT may boost the numbers of women turning to the
supplements.
The supplements do have other potential health benefits.
Women in the Far East, whose regular diet includes relatively
large amounts of soy, have much lower cancer rates than
Western women.
But some studies highlighted possible downsides. Soy
isoflavones have been show to interfere with estrogen function
in rats, decreasing some of the brain molecules involved in
social and sexual behaviour. And a specific isoflavone called
genistein prevents the tumour-fighting drug tamoxifen from
working in mice. The new study, showing that a soy isoflavone
has negative effects on sexual behavior in rats, joins these.
Encouraging behaviour
When female rats are on heat, they typically encourage nearby
male rats by changing their posture. Once a male rat has
approached, they change their position to be more receptive to
their mate.
Heather Patisaul and colleagues at Emory University in
Atlanta, Georgia, gave female rats small doses of soy
supplement. This produced blood levels of the isoflavone
similar those in women regularly taking the supplements.
The "encouraging behaviours" in the rats decreased by 70
per cent, while the "receptive behaviours" decreased by up
to 40 per cent.
The breast cancer drug tamoxifen, which opposes the function
of estrogen in some tissue, had a similar but smaller effect.
This, with evidence from other studies, leads Patisaul to
believe that the soy isoflavone is also acting as an
"estrogen opposer".
She adds that there is anecdotal evidence of decreased sex
drive in women taking tamoxifen, as well as problems with
vaginal dryness.
Confounding factor
Patisaul does not know if any such side effects have been
reported in women taking soy supplements. But she notes that
since most women take them for menopause, it would be
difficult for women to tell if changes in sex drive were due
to the pill or changing hormones.
"You would need to do a controlled clinical trial to sort it
out," she says. "But no one has asked these women about sexual
side effects. We need to look at all aspects of what [these
compounds] are doing."
Andrew Kaunitz, at the University of Florida in Jacksonville
and a researcher with the women's health initiative, agrees
that this should be looked into. "Interest in soy has
increased in recent years," he says.
The new study was presented on Wednesday at the Society for
Neurosciences meeting in New Orleans.
Emily Singer