WASHINGTON: In a study that shows more than ever you are what you eat, US scientists said on Friday they had changed the coat colours of baby mice simply by altering their mothers’ diets.

The study shows that common nutrients can influence which genes turn on and off in a developing fetus, and help explain some of the factors that decide which genes “express” and which remain silent.

Writing in Friday’s issue of the journal Molecular and Cellular Biology, the scientists at Duke University Medical Center said they changed the colour of baby mouse fur by feeding pregnant mice four supplements — vitamin B12, folic acid, choline and betaine.

Mice given the four supplements gave birth to babies predominantly with brown coats. Pregnant mice not fed the supplements gave birth mostly to babies with yellow coats.

Careful study showed the extra nutrients turned down expression of a gene called Agouti, which affects fur colour.

“We have long known that maternal nutrition profoundly impacts disease susceptibility in their offspring, but we never understood the cause-and-effect link,” said Randy Jirtle, a professor of radiation oncology at Duke who directed the study.

“For the first time ever, we have shown precisely how nutritional supplementation to the mother can permanently alter gene expression in her offspring without altering the genes themselves,” he said in a statement.

The findings have not been shown in humans, but the researchers said there is much support for the idea that nutrition can affect gene expression in people.

Several studies have shown, for instance, that women who eat a poor diet while pregnant have children who grow up with a tendency to diabetes and heart disease.

OBESITY, DIABETES LINK: This study could help explain that. The Agouti gene not only affects coat colour, but also metabolic factors involved in diabetes and heart disease.—Reuters