Do you love a flaky croissant along with your morning coffee? A diet that’s rich in simple carbohydrates like that croissant (quickly transformed into sugar in your bloodstream) raises the risk of heart disease for women, a new Italian study has found.
The same effect, however, is not seen in men, according to the report, published April 12, 2010 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.
Dr. Victoria Drake, director of the Micronutrient Information Center at the Linus Pauling Institute of Oregon State University explains:
“A high glycemic index is known to increase the concentration of triglycerides in the blood and lower the concentration of HDL (good) cholesterol. Those adverse effects make it a stronger risk factor for heart disease.”
Surprisingly, 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, Dr. Drake added. “There is definitely a gender difference.”
The Italian researchers got their information on dietary intake from questionnaires filled out by 15,171 men and 32,578 women. After 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 actually associated with higher intake of high-glycemic foods, not just carbs. Researchers concluded:
“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.”
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.
Brown rice, for example, has a glycemic index of 55 compared to a baked potato’s 76. But in the traditional system of classifying carbohydrates, both brown rice and baked potato would be similarly classified as complex carbohydrates despite the difference in their effects on blood glucose levels.
Even four little bitty dry soda crackers carry a whopping glycemic index of 74.
Fifteen out of 16 published studies have found that, compared to high-glycemic index foods, the consumption of low-glycemic index foods:
- delayed the return of hunger
- decreased subsequent food intake
- increased satiety (feeling full)
In the first two hours after a meal, blood glucose and insulin levels rise higher after a high-glycemic load meal than they do after a low-glycemic load meal containing equal calories.
But wait – as if that flaky croissant doesn’t raise those blood glucose and insulin levels high and fast enough, consider what happens if you enjoy it alongside a cup of coffee.
My favourite breakfast (whole grain Cheerios with half a banana sliced on top, skim milk and coffee) sounds harmless and relatively healthy, but if I have coffee with it (as I like to do each morning), I may be raising my blood sugar level by a whopping 250% compared to drinking decaf coffee with my cereal.
So say researchers at Canada’s University of Guelph, who reported their 2008 findings in the American Journal of Clinical Nutrition. Since about 65% of coffee consumption in North America occurs during breakfast hours, this involves a lot of us. The study’s authors reported:
“Caffeine interferes with our body’s response to insulin. It makes us resistant to insulin, which in turn makes our blood-sugar levels go higher.”
In fact, combining the caffeinated coffee and low-sugar cereal resulted in higher blood-sugar levels than when the subjects drank decaffeinated coffee before eating cereal with even more sugar.
Researchers’ recommendation? Drink decaf in the morning when you’re eating cereal or other high carb foods.
Meanwhile, the Italian researchers suggest that their gender difference might be due to the action of male hormones called androgens that appear to slow the transformation of carbohydrates into blood sugar, whereas the female hormone estrogen speeds the process.
It’s not all sweetness and light in choosing low glycemic index foods, however. The world-famous Mayo Clinic offers pros and cons when considering this option. For example, the glycemic index doesn’t consider all variables that affect blood sugar, such as how food is prepared or how much is eaten.
Dr. Suzanne Steinbaum, director of Women and Heart Disease at Lenox Hill Hospital in New York City, said the Italian study does show the need for women to be more aware of the nature of the carbohydrates in their diet. She warns:
“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. There’s a simple way to determine the glycemic index of all processed food. Read the label! 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 1 gram. Dr. Steinbaum adds:
“If you see a high level of sugar, that’s the one to stay away from.”
The Linus Pauling Institute has more about the glycemic index.
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