Women on Atkins-style diets are putting themselves at risk of heart disease and strokes, experts say.
Those who regularly eat a low-carbohydrate, high-protein diet are at greater risk of cardiovascular disease than those who do not participate in such diets, research published on bmj.com suggests.
More than 43,000 Swedish women were assessed over 15 years. Of those, 1,270 had suffered a "cardiovascular event".
From a dietary survey, the researchers found that if women decreased their carb intake by 20 grams a day and increased their protein intake by 5g, they had a five per cent increased risk of cardiovascular disease.
The amounts are relatively small - 20g of carbohydrates is the equivalent of a small bread roll and 5g of protein is equivalent to one boiled egg.
The figures represent an additional four to five cases of cardiovascular disease per 10,000 women a year compared with those who did not regularly eat a low-carbohydrate, high-protein diet.
The authors said that increasing the level of education and physical activity reduced the risk of cardiovascular disease, while increasing levels of smoking increased the risk.
"Low-carbohydrate, high-protein diets, used on a regular basis and without consideration of the nature of carbohydrates or the source of proteins, are associated with increased risk of cardiovascular disease," the authors concluded.
Such diets are frequently used to lose weight and are favoured by many celebrities as a method to keep trim.
Colette Heimowitz, vice-president of nutrition and education for Atkins Nutritionals, said the study was "misleading".
She said that long-term adherence to low-carbohydrate diets requires carefully considered food choices, which the Atkins diet teaches in all educational materials, published books and communications.
"The authors of the report even conclude that low-carbohydrate, high-protein diets are only associated with cardiovascular risk when used on a regular basis, without consideration of the nature of carbohydrates or the source of proteins," she said.
"In stark contrast, Atkins is a nutritional strategy which stresses nutrient-dense carbohydrates as part of a balanced eating plan and includes a variety of protein and good fats, while restricting carbohydrates which have the greatest impact on blood sugar."