Key points

Key quote
“The study subjects were mice, which are herbivores. Whether or not these findings or effects would apply to humans, who are omnivores, is unknown” – Dr Stuart Trager, medical director of Atkins Nutritionals Inc

Story in full WOMEN who strictly follow the Atkins diet could be damaging their chances of getting pregnant, according to new research.

Eating too much protein can prevent an embryo attaching to the wall of the womb or hinder its early development, the findings suggest.

Although the research was done on mice, scientists believe there are implications for humans, especially people on Atkins-style diets.

“It’s conceivable that people who have protein intakes greater than 30 per cent may have problems conceiving,” said Dr David Gardner, who led the American study.

The upper limit for protein consumption under Atkins guidelines is 35 per cent of total calories, but devout disciples of the diet might consume a greater proportion.

The research stems from the observation that protein in the diet affects levels of ammonium in the female reproductive tract. In herbivorous animals such as cows this has been known to cause reproductive problems.

Previous studies have shown that ammonium harms mouse embryos grown in the laboratory, causing genetic effects and retarding development.

Dr Gardner, the scientific director of the Colorado Centre for Reproductive Medicine in Englewood, set out to discover whether the same effects occurred in living mice.

The scientists found that ammonium levels in the oviduct, where the early embryo forms, were four times higher in mice given the high protein diet.

Four-day-old embryos in these animals had fewer cell numbers and a higher rate of cell death.

This is a crucial stage in embryonic development, since it is just before the embryo attaches to the inside of the womb. Without implantation, pregnancy cannot occur.

A total of 174 young embryos were transferred from both groups of mice to surrogate mothers fed a normal diet.

Despite the switch, only 65 per cent of those taken from high protein mice developed into a foetus. In contrast, embryos from mice on the lower protein diet had an 81 per cent success rate.

Protein consumption also had a striking effect on a reproductive genetic mechanism called imprinting, which causes certain genes to be switched on only if they come from a particular parent.

The HI9 gene, which is important to growth and development, is supposed to be activated only if inherited from the mother. But in two-thirds of embryos from mice on high protein diets, it was the father’s HI9 gene that was switched on.

Subsequently, these embryos were unable to grow properly in the womb.

Dr Gardner, who presented the findings yesterday at the annual meeting of the European Society of Human Reproduction and Embryology (ESHRE), in Berlin, said: “One has to start off with the assumption that the mouse is generally more of a herbivorous animal than we are, and like a cow, is less able to metabolise high amounts of protein.

“But what you can say is that where people put themselves on very high protein diets they may have some difficulties trying to conceive.”

He said most people on the Atkins diet did not appear to have elevated ammonium levels but the same may not apply to individuals eating very high amounts of protein.

“We would like to look at what people say they are eating and circulating levels of ammonium,” he added. “That’s the next phase of our research.”

Dr Gardner said that to be safe, couples trying to conceive should ensure the woman’s protein intake is less than 20 per cent of her total energy consumption.

Dr Stuart Trager, medical director of Atkins Nutritionals Inc, said: “In regards to the research presented by Dr David Gardner at the 20th annual conference of the European Society of Human Reproduction and Embryology, it is essential to clarify and define the research results as well as the Atkins Nutritional Approach.

“It is important to note that there was no mention of carbohydrate control in the research conducted by Dr Gardner. 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.

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

“In fact, some studies show a positive correlation between controlling carbohydrates and female fertility.”