The study, which was carried out by Swedish and US researchers, monitored 43,000 women in the Uppsala region between 1991 and 1992, a time before low carb diets became popular in Sweden.
The report, which is one of the biggest studies into the long term effects of carbohydrates, revealed that a diet with extra proteins, especially protein from meat, can prove dangerous for some women.
“Those who want to lose weight should not unquestioningly give themselves to the popular weight loss programmes like the Atkins diet and LCHF (Low Carb High Fat) and be blinded by short term results,” said Hans-Olov Adami, professor of Cancer Epidemiology at the Karolinska Institute to the Dagens Nyheter newspaper.
“One must also think of the long term health effects.”
Of the women studied, 1,270 suffered heart attacks or strokes and the risk of falling sick grew in correspondence with lower carbohydrates together with more protein.
High amounts of proteins from vegetables and plants in food were less dangerous than high amounts of animal protein.
A lowering of carbohydrates by 20 grammes (roughly the amount in a small bread roll) together with an increased protein intake of 5 grammes (roughly that of a boiled egg) will increase the risk for heart diseases by five percent.
The findings were published in The British Medical Journal on Wednesday.