There could be more heart- disease dangers in your diet than the usual suspects. By Paula Goodyer .
WHEN CONSIDERING which foods increase the risk of heart disease, you might think of fatty bacon rashers, but not a bowl of refined breakfast cereal. But to defend arteries from the thickening and hardening that can lead to heart disease and stroke, it might pay to be choosy about your carbs.
We're all familiar with the standard dietary advice to head off heart disease - avoid saturated fat and trans fats in favour of healthier fats. But, according to Professor Jennie Brand-Miller of the School of Molecular Biosciences at the University of Sydney, there's growing evidence that too many carbohydrates with a high Glycemic Index (GI) - the kind that cause rapid rises in blood sugar - may also contribute to heart disease.
The trouble with a diet heavy on rapidly digested carbohydrate foods - such as many white breads, refined breakfast cereals, processed snack foods, biscuits and potatoes - is their potential to increase levels of blood glucose. High levels of glucose are "toxic" to arteries, Brand-Miller explains. "Not only do they encourage plaque to form in the artery walls, they also cause inflammation that ages arteries, making them stiffer and less elastic, while also increasing the formation of blood clots."
And it's not just people with diabetes who are likely to have high blood glucose levels either - increasing numbers of Kiwis and Australians now have blood glucose levels that hover somewhere between normal and diabetic, and that's not healthy.
"This isn't saying that high GI carbohydrates are the only villain as far as arteries are concerned - it means we need to beware of both too much saturated fat and too many high GI carbohydrates," says Brand-Miller. "It's the quality of both carbohydrates and fat that influence heart health. Carbs and fat both taste good - but we have to be choosy about which type we eat."
Some research also suggests women's hearts may be more easily damaged by high GI carbs than those of men. A study recently published in the Archives of Internal Medicine found that in women, but not men, a high carb intake more than doubled the risk of developing heart disease over an eight-year period. Eating more high GI carbs seemed to increase the risk, while eating more low GI carbs did not. But with men it was a different story - the amount of carbohydrate foods and their GI rating didn't seem to matter - at least not to their heart health.
Why carbs should have an effect in women, but not men, isn't clear, but Brand- Miller speculates that heart disease might develop in a different way in women compared to men.
"Some research has found that a predictor of heart disease in women is a high level of C-reactive protein (CRP), a substance measured in blood that's a sign of inflammation. This low grade inflammation is probably a result of oxidative stress - and this fits in with the idea that a high GI diet can increase oxidative stress. A study at the University of Sydney has suggested that women may be more vulnerable to the effects of high GI carbohydrates on weight gain, but it's only a hypothesis - we don't know for sure."
None of this is to say that you should never bake a potato or eat toasted Turkish but it does suggest it's not smart to let refined carbs and potatoes dominate your diet. And not just for your heart's sake either.
A broad mix of vegetables and eating denser, grainier breads delivers a lot more heart healthy nutrients and fibre.