Excess protein could affect pregnancy chances

Dr. Kirsty Horsey

Progress Educational Trust

28 June 2004

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[BioNews, London] BioNews reporting from ESHRE conference, Berlin:

High protein diets could affect a woman's chances of becoming pregnant, a US study carried out on mice suggests. The research, reported at the European Society of Human Reproduction and Embryology (ESHRE) annual meeting in Berlin, suggest that women trying to conceive should avoid 'low carbohydrate' regimes such as the Atkins diet, which feature high amounts of protein and fats. Study leader, David Gardner, of the Colorado Center for Reproductive Medicine, stresses that the effect of diet on mice may not reflect the situation in humans. However, he said that women adhering strictly to high protein diets may have problems conceiving.

The researchers studied embryos grown in the laboratory, produced by mice fed by a diet containing either 25 or 14 per cent protein for four weeks. They found that the high protein diet appeared to disrupt a process called genomic imprinting: the switching off of certain genes in the early embryo, according to whether they are inherited from the mother or father. The diet also affected the ability of the embryos to implant in the womb and the development of the fetus. 'Although our investigations were conducted in mice, our data may have implications for diet and reproduction in humans', said Gardner.

Previous studies have shown that the amount of protein in the diet affects the levels of ammonia in the reproductive tract in cows and mice, and also that ammonia can harm mouse embryos grown in the laboratory. The latest study focused on an imprinted gene called H19, which is involved in embryo growth. The scientists found that only 36 per cent of the embryos from mated mice fed on a high protein diet showed normal H19 gene activity, compared with 70 per cent of the control group. 'Furthermore, only 65 per cent of the embryos in the high protein group developed into fetuses once they had been transferred, compared to 81 per cent in the control group', said Gardner. And, of the embryos that did implant, only 84 per cent developed further, compared to 99 per cent of the control group.

The researchers conclude that their findings, together with similar work carried out on cows, show that women trying to conceive should make sure their protein intake is 'less than 20 per cent of their total energy intake'. An average US diet apparently contains around 14 per cent protein.

Reproduced with permission from BioNews, an email and online sources of news, information and comment on assisted reproduction and genetics.