Eating a high protein diet may make it more difficult for women to conceive, American researchers said on Monday.

Dr David Gardner, of the Colorado Center for Reproductive Medicine in Englewood, said diets containing 25 percent protein disrupt the development of early mice embryos and may have a similar impact in humans.

“Although our investigations were conducted in mice, our data may have implications for diet and reproduction in humans,” Gardner told a fertility meeting.

In mice the high protein diet seems to interfere with a genetic process known as imprinting, which controls the activity of genes inherited from the father and mother.

The researchers fed mice a diet of either 25 percent or 14 percent protein for four weeks before mating them. Afterwards they examined 42 of the resulting early embryos, which are known as blastocysts, to see if imprinting for an important growth gene was altered.

They also transferred 174 early embryos into the wombs of mice that were eating a normal diet to study the impact of maternal diet before implantation on fetal development.

“We found only 36 percent of blastocysts developed in mothers on the 25 percent diet showed a normal imprinting pattern, compared to 70 percent in the control group,” Gardner explained.

Fewer embryos in the high protein group developed into fetuses - 65 percent compared to 81 percent in the lower protein group.

“These findings, together with similar work carried out in cows means that it would be prudent to advise couples who are trying to conceive…to ensure that the woman’s protein intake is less than 20 percent of their total energy consumption,” Gardner told the European Society of Human Reproduction and Embryology.

“The available data certainly indicate that a high protein diet is not advisable while trying to conceive,” he added.

But Dr Stuart Trager, the medical director of Atkins Nutritionals Inc, which developed the low-carbohydrate Atkins Diet, said some studies have shown a positive correlation between controlling carbohydrates and female fertility.

“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 cannot be replicated in humans,” Trager said in a statement.

“This casts a large discrepancy on the ability to derive conclusions about the clinical implications of this study with regard to humans,” he added.