A diet rich in carbohydrates that are quickly transformed into sugar in the blood raises the risk of heart disease for women, a new Italian study finds. The same effect, however, is not seen in men, according to the report in the Archives of Internal Medicine.
The study, by researchers at Italy's National Cancer Institute, looked not only at total carbohydrate intake but also at what is known as the glycemic index of those carbohydrates -- a measure of how quickly and to what extent blood sugar rises after intake of specific carbohydrates.
Carbohydrate foods with similar calorie content can show widely different scores on the glycemic index. Carbohydrates with a high glycemic index include corn flakes, white bread and white rice. Those with lower scores include whole wheat products and sweet potatoes.
"A high glycemic index is known to increase the concentration of triglycerides and lower the concentration of HDL cholesterol, the good kind," explained Victoria J. Drake, director of the Micronutrient Information Center at the Linus Pauling Institute of Oregon State University, who has studied the subject. "Those adverse effects make it a stronger risk factor for heart disease."
How the study was done
The Italian researchers got their information on dietary intake from questionnaires filled out by 15 171 men and 32 578 women. Following them for nearly eight years, the researchers found that women who consumed the most carbohydrates overall had about twice the incidence of heart disease as those who consumed the least. Closer analysis showed that the risk was associated with higher intake of high-glycemic foods.
"Thus, a high consumption of carbohydrates from high-glycemic index foods, rather than the overall quantity of carbohydrates consumed, appears to influence the influence of developing coronary heart disease," the researchers wrote.
Previous studies have seen the same effect in other groups of women, Drake said. They include the Nurses Health Study, done in the United States, and studies of women in the Netherlands.
No effect from total carbohydrate consumption or consumption of foods with a high-glycemic index was seen in men in the Italian study, a pattern also seen in other studies, Drake added.
"There is definitely a gender difference," she noted.
Male hormones slow process
The difference might be due to the action of sex hormones, the researchers speculate. Male hormones, androgens, appear to slow the transformation of carbohydrates into blood sugar, whereas the female hormone oestrogen speeds the process, she said.
Dr Suzanne Steinbaum, director of women and heart disease at Lenox Hill Hospital in New York City, said the study shows the need for women to be more aware of the nature of the carbohydrates in their diet.
"An emphasis needs to be placed on a diet that is not simply low in carbohydrates but rather low in simple sugars, as measured by the glycemic index," Steinbaum said.
There's a simple way to determine the glycemic index of a food, she said.
"Look at the label," Steinbaum said. "It says 'carbohydrates.' Under that, it says 'sugars.' When you have a high number for sugars, that's a way to know what the glycemic index is."
That index can differ widely in foods that don't appear to be different, she said. One breakfast cereal may have a sugar content of 16 grams, but another may have just three to six grams.
"If you see a high level of sugar, that's the one to stay away from," Steinbaum said. - (HealthDay News, April 2010)