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
A broad mix of vegetables and eating denser, grainier breads
delivers a lot more heart healthy nutrients and fibre.