High GI and GL foods linked with significantly increased risk of diabetes

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Previously, for instance here, I have attempted to point out that the conventional dietary advice so often given to diabetics is nonsensical and likely to be positively damaging to their health. Why diabetics should be advised to ‘include starch with every meal’ and therefore almost certainly ensure they’re going to get quite a shot of sugar into the system (just what a diabetic needs to avoid) is beyond me.

It also makes sense is that if you don’t have diabetes and want it to stay that way you might think about not eating to many foods that give brisk and substantial release of sugar into the bloodstream.

In theory, a diet rich in high glycaemic index (GI) foods may, theoretically at least, increase the risk of type 2 diabetes by causing excesses of insulin and thereby increasing the risk that the body will become resistant to the effects of this hormone in time. Also, a high demand for insulin can cause the pancreas which secretes it to become ‘exhausted’, which can lead to diabetes through a relative lack of this insulin.

This week saw the publication of a couple of studies which support the idea that if we don’t want to head down the road to diabetes, we may do well to be mindful of those carbs.

Both of the studies in question were published in the Archives of Internal Medicine. The first of these studies employed 59,000 black American women as their subjects [1]. The women were followed for an average of eight years. Over this time, the researchers assessed the relationship between the overall glycaemic index of the diet and risk of diabetes. Women consuming the highest GI diet, compared to the lowest, were found to be at a 21 per cent increased risk of developing diabetes.

On the other hand, intake of fibre from grain was found to be associated with relative protection from diabetes: women consuming the most cereal fibre were found to be at a 18 per cent reduced risk of developing diabetes compared to those consuming the least.

Interestingly, this study found that the associations between GI, fibre and diabetes risk were strongest in women with a body mass index (BMI ” calculated by dividing weight in Kg by the square of one’s height in metres) of less than 25. In these individuals, who traditionally are regarded as being of ‘healthy’ weight, a high GI diet was associated with a 91 per cent increased risk of diabetes while high cereal fibre was associated with a 59 per cent reduced risk.

The second of the studies published this week was undertaken in China. Again, the study focused exclusively on women: more than 64,000 women, assessed over a period of about 4½ years.

This study also found that women eating the highest GI diet were at increased risk of developing diabetes ” to the tune of 21 per cent. The researchers also assessed the relationship between glycaemic load (essentially an overall measure of the extent to which a diet raises blood sugar levels) and risk of diabetes. Here, the highest GL diets were associated with a 34 per cent increased risk of diabetes. The researchers also analysed the relationship between rice (a relatively high GI and GL food) consumption and diabetes risk. They found that women eating the most rice compared to those eating the least were at a 78 per cent increased risk of diabetes.

OK, so this sort of evidence is not perfect, not least of all because these studies are ‘epidemiological’ in nature. So, while they show that high GI and GL diets are associated with an increased risk of diabetes, it is not assured that it’s the high GI/GL nature of the diet that is causing the diabetes.

However, if just think for a moment the effects high GI/GL foods have on blood sugar levels and insulin secretion, and then think about how this may lead to insulin resistance and/or pancreatic exhaustion, then it does not take too much imagination, I think, to see how eating such foods may hasten us down a path to diabetes.

This evidence, I reckon, should really cause us to question the so-often quoted wisdom of including a starch food with every meal. Here in the UK, the Food Standards Agency recommends that a third of our diet should come from these foods. This despite a mound of evidence that such foods appear to pose significant risks for our health.


1. Krishnan S, et al. Glycemic Index, Glycemic Load, and Cereal Fiber Intake and Risk of Type 2 Diabetes in US Black Women. Arch Intern Med. 2007;167(21):2304-2309.

2. Villegas R, et al. Prospective Study of Dietary Carbohydrates, Glycemic Index, Glycemic Load, and Incidence of Type 2 Diabetes Mellitus in Middle-aged Chinese Women. Arch Intern Med. 2007;167(21):2310-2316.

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