GI Symbol News with Dr Alan Barclay
Better heart health with a low GI diet
These days, most people are aware of the importance of cutting back the saturated fat and choosing the good fats for heart health. What they are much less aware of is that being choosy about the carbs they eat can also help prevent heart disease.
Heart disease doesn’t just happen Your risk of developing it is determined by things you cannot change, such as genetic (inherited) factors and things you can do something about. Things you cannot change include: your ethnic background, being male, being older, having a family history of heart disease, being post-menopausal. Things you can do something about include: smoking, having high blood pressure, having high blood glucose levels, having high blood cholesterol, high triglycerides, and low levels of the ‘good’ (HDL) cholesterol, having high CRP (C-reactive protein) levels (a marker of low-grade chronic inflammation somewhere in the body), being overweight or obese and being sedentary.
That’s why public health programs around the world focus on encouraging you to quit smoking, be more active every day, lose weight, drop the salt (sodium) and cut back the saturated fat.
The saturated fat message, however, is a little more complicated than was first thought While eating less saturated fat – particularly from fatty processed meats – is prudent advice, we now know that what you replace it with is critical when it comes to preventing heart disease. For example, replacing saturated fats with quality unsaturated fats like olive, peanut and sesame oils and eating a handful of nuts can reduce your risk of developing heart disease by reducing the ‘bad’ LDL cholesterol and increasing the ‘good’ protective high-density-lipoprotein (HDL) cholesterol. On the other hand, replacing saturated fats with highly refined carbohydrate (sugars, oligosaccharides and starches) does not reduce your risk at all.
Carb quality counts A new systematic review by Mirrahimi and colleagues has added further evidence to the message that the quality and amount of carbohydrate you eat really counts. When they reviewed 12 population-based studies (230,000 people followed up over a period of 6–25 years and nearly 7,000 heart attacks) they found that women who ate a high GI (59) or GL (160) diet had a significantly increased risk (26% and 55%, respectively) of having a heart attack, compared to women who consumed a low GI (51) and GL (95) diet.
However, they found no association between GI or GL and risk of having a heart attack in men in these particular studies. Why? Well, apart from the fact that there were nearly three times more women than men in the combined studies and that women may report their dietary habits more accurately, we need to remember that part of the protection that women have from heart disease may be related to their normally high ‘good’ (HDL) cholesterol levels. As high GI and GL diets tend to reduce HDL cholesterol concentrations, this may disproportionately increase heart disease risk in women, especially after menopause. At the same time, high-GI diets may raise triglyceride levels, which may also increase women’s risk. Needless to say, more studies in men are of course needed to investigate this issue further.
The bottom line Routinely advising people to ‘eat less saturated fat’ may not be sufficient to reduce their risk of having a heart attack or stroke. Health professionals and heart health organisations need to encourage people to replace saturated fats with quality unsaturated fats and/or low GI carbs.
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For more information about the GI Symbol Program
Dr Alan W Barclay, PhD
Chief Scientific Officer
Glycemic Index Foundation (Ltd)
Phone: +61 (0)2 9785 1037
Mob: +61 (0)416 111 046
Fax: +61 (0)2 9785 1037