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Tuesday, June 29, 2004
Researchers in Colorado revealed
at a European fertility conference that embryos from mice
that had been fed a high protein diet
showed a failure to implant in the womb. They believe the results
should be a warning to women who want children.
"Although our
investigations were conducted in mice, our data may have implications
for diet and reproduction in humans," said David Gardner, scientific
director of the Colorado Centre for Reproductive Medicine in
Englewood.
Some 3 million people in the UK and 30 million in
the US are believed to have tried the controversial Atkins
diet, which advocates high meat, fish and egg consumption and
severely limited intake of carbohydrates such as bread, rice,
pasta and starchy vegetables.
Animal research has previously
shown that the amount of protein in the diet can affect the
levels of ammonium in the female reproductive tract of cows
and mice.
Laboratory tests have also demonstrated that ammonium
can interfere with the development of mouse embryos. It appears
to affect the H19 gene, found on chromosome 7, which is important
to growth.
The Colorado team fed mice a diet which contained
a relatively high 25% protein. A control group were given a
diet which was 14% protein.
People trying to lose weight on
the Atkins diet tend to consume around 35% protein initially,
dropping to 25% later, although Atkins representatives say
there is no upper limit to the amount of protein that can be
consumed.
"We definitely don't set a limit on how much protein
people should eat. It's as much protein as you need to eat
until you are full. Protein is quite satisfying so people don't
tend to overeat," said a spokeswoman.
In the study, detailed
at the European Society of Human Reproduction and Embryology
conference in Berlin, only a third of the mice (36%) on the
high protein diet developed with a normal H19 gene, as opposed
to 70% of the control group.
Of the embryos in the high protein
group, only 65% developed into foetuses once they had been
transferred to the womb, compared with 81% in the control group.
"Not
only did fewer embryos develop into foetuses when transferred
from the high protein group, but of all the embryos that implanted,
only 84% developed further, whereas in the control group 99%
of the embryos that implanted continued to develop," said Dr
Gardner.
By the 15th day of gestation, foetuses from the high
protein group were a third of a day behind the control group
in their development.
One foetus had a neural tube defect -
damage to that part of the foetus which becomes the spinal
cord or brain. In humans the defect most commonly leads to
spina bifida.
"These findings, together with similar work carried
out in cows, mean that it would be prudent to advise couples
who are trying to conceive, either naturally or via ART [assisted
reproduction technology], to ensure that the woman's protein
intake is less than 20% of their total energy consumption," said
Dr Gardner. "The available data certainly indicate that a high
protein diet is not advisable while trying to conceive."
A
spokesman for Atkins Nutritionals Inc cast doubt on the findings. "It
is important to note that there was no mention of carbohydrate
control in the research conducted by Dr Gardner," he said. "The
study subjects were mice, which are herbivores. Whether or
not these findings or effects would apply to humans, who are
omnivores, is unknown."
Ben Gocial, a reproductive endocrinologist
from Thomas Jefferson University Hospital, speaking on behalf
of Atkins, said that controlling carbohydrate consumption had
been shown to have a positive effect in women who were trying
to conceive and who were over-weight and/or not ovulating properly.
The Guardian
© Guardian Newspapers Limited
2004
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Infertility