High-protein diets linked to infertility

Popular high-protein diets, such as Atkins, can hinder a woman's ability to conceive, according to a study released Monday.

In the study, a group of mice fed a high-protein diet developed higher levels of ammonium in the females' reproductive tracts than those normally found. Previous studies have shown ammonium to negatively affect genes and slow development of mouse embryos and also to affect an embryo's ability to attach to the womb.

David Gardner, scientific director for the Center for Reproductive Medicine in Englewood, Colo., led the study.

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

Ammonium levels in the high-protein mice were four times higher in the oviduct, where the early embryo forms, than in mice on a typical diet.

The compound of nitrogen and hydrogen also can alter certain genes that react differently depending on whether they are inherited from the mother or father. This process, called genetic imprinting, also was affected negatively by ammonium levels during the study. Specifically, the H19 gene, which is involved in growth, was altered.

"These data show that eating a moderately high-protein diet, which results in elevated ammonium levels in the female reproductive tract, adversely affects the pre-implantation embryo in the living animal," Mr. Gardner said.

Atkins diet guidelines suggest that protein consumption remains below 35 percent of total calories for those on carbohydrate-restricted diets. The standard laboratory diet for mice is 14 percent protein. The mice used in the study were given a diet of 25 percent protein.

Atkins Nutritionals spokesmen distinguished between carbohydrate-controlled diets and high-protein diets, also adding that mice, which are herbivores, may have a different tolerance for ammonium levels than meat-eating animals.

"The positive role of controlled-carbohydrate nutrition has been well-established clinically in women who are either overweight and/or not ovulating normally," said Dr. Ben Gocial, a reproductive endocrinologist from Thomas Jefferson University Hospital in Philadelphia.

Studies using mice have been shown to stray from medical possibilities in humans, said Dr. Stuart Trager, medical director for Atkins Nutritionals. He cited a study in which mice embryos were produced from a single parent, a process incapable of human duplication.

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

Dr. Amy Lanou, a nutritionist with the Physicians Committee for Responsible Medicine, said the study elicits cause for concern.

"I don't think anyone trying to conceive or [who is] pregnant should be on a high-protein diet," she said.

The research was presented Monday at the 20th annual conference of the European Society of Human Reproduction and Embryology in Berlin.