High protein could impact conception rate, suggests mouse study

Related tags High protein Embryo Pregnancy

A moderately high protein diet could reduce a woman's chances of
becoming pregnant, according to new research presented at the
European Society of Human Reproduction and Embryology
annual conference in Berlin yesterday.

A US team said that a diet containing 25 per cent protein disrupted the normal genetic imprinting pattern in mice embryos at a very early stage in their development. The diet also adversely affected subsequent embryo implantation in the womb and foetal development.

The research, led by Dr David Gardner, scientific director of the Colorado Center for Reproductive Medicine in the US, could have important implications for people following one of the high-protein weight loss diets, currently fashionable in the US and UK.

"Although our investigations were conducted in mice, our data may have implications for diet and reproduction in humans,"​ said Dr Gardner.

Atkins Nutritionals, the company behind the low-carboydrate Atkins diet, noted in a statement that "there was no mention of carbohydrate control in the research"​. Followers of the Atkins diet tend however to replace carboydrates with protein, increasing their daily protein intake.

Stuart Trager, medical director for Atkins Nutritionals, added that the study subjects were mice, which are herbivores. Whether or not these findings or effects would apply to humans, who are omnivores, is unknown.

"The differences between mice and human embryos have recently been demonstrated by the ability to produce mice embryos from a single parent, a process that can not be replicated in humans,"​ said Trager. "This casts a large discrepancy on the ability to derive conclusions about the clinical implications of this study with regard to humans."

However Dr Gardner said his 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, to ensure that the woman's protein intake is less than 20 per cent of their total energy consumption.

"The available data certainly indicate that a high protein diet is not advisable while trying to conceive."

Previous research has shown that the amount of protein in the diet affects the levels of ammonium within the female reproductive tract in cows and mice. It is known that ammonium adversely affects mouse embryos developed in culture in the laboratory, inducing altered imprinting of the H19 gene and retarding foetal development. The H19 gene, found on chromosome 7, is an important gene involved in growth.

Normally, genes act in the same way, whether they are transmitted by the mother, or the father. But, a few genes break this genetic rule. Whether they are switched on (expressed) or off depends on whether they are inherited from the mother or the father. The process of inheriting specifically from the mother or the father is called imprinting.

Dr Gardner fed mice on a diet containing either 25 per cent protein (moderately high) or 14 per cent protein (the amount contained in the average US diet, according to the American Heart Association) as the control group for four weeks.

The mice were mated and 42 of the resulting blastocysts (early embryos)were examined to discover the imprinting status of the H19 gene; 174 blastocysts from mice on both diets were transferred to mice eating a normal diet in order to discover the effects of the maternal diet during the preimplantation stages on subsequent foetal development.

"We found that only 36 per cent of blastocysts developed in mothers on the 25 per cent protein diet showed a normal imprinting pattern, compared to 70 per cent in the control group,"​ said Dr Gardner.

"Furthermore, only 65 per cent of the embryos in the high protein group developed into foetuses once they had been transferred, compared to 81 per cent in the control group."

He added that not only did fewer embryos develop into foetuses when transferred from the high protein group, but of all the embryos that implanted, only 84 per cent developed further, whereas in the control group 99 per cent of the embryos that implanted continued to develop.

"Analysis of foetal development on the 15th day of gestation showed that foetuses from the high protein group were a third of a day behind the control group in their development, and one foetus had a neural tube defect,"​ said Dr Gardner.

"These data show that eating a moderately high protein diet, which results in elevated ammonium levels in the female reproductive tract, adversely affects the preimplantation embryo in the living animal. Our observations are consistent with data on embryos developed in the laboratory in the presence of ammonium,"​ he continued.

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