Scientists believe low-carbohydrate slimming diets could damage arteries and increase the risk of heart attacks.
Research suggests the regrowth and repair of blood vessels may be impaired by cutting out carbohydrates with an Atkins-style diet.
In the study, published in the journal Proceedings of the National Academy of Sciences, the researchers tested heart disease-prone mice given three types of diet.
They concluded that levels of cholesterol, triglyceride blood fats and inflammation markers normally associated with atherosclerosis could not account for the findings.
Their measurements were roughly equal for mice fed both Western and low-carbohydrate diets.
However, when researchers examined the numbers of endothelial progenitor cells (EPCs) - used to repair or grow new blood vessels - that the mice were producing, they noticed a dramatic difference.
Study leader Professor Anthony Rosenzweig, director of cardiovascular research at the Beth Israel Deaconess Medical Center in Boston, said: "Examinations of the animals' bone marrow and peripheral blood showed that the measures of EPC cells dropped fully 40% among the mice on the low-carbohydrate diet - after only two weeks."