Low GI Diets May Prevent Risk of Type 2 Diabetes and Heart Disease

11/03/08 The first meta-analysis to evaluate the association between the GI (glycemic index) and GL (glycemic load) of the diet, and the risk of developing common lifestyle-related diseases was published in the American Journal of Clinical Nutrition March 1 [2008; 87 (3)].

The study provides compelling evidence that diets with a high GI or a high GL will increase your risk of type 2 diabetes and heart disease. It also shows there is good evidence for links between high blood glucose and gall stones and some types of cancer.

Conducted by Alan Barclay, Joanna McMillan Price, Prof Jennie Brand-Miller and colleagues, the meta-analysis systematically reviewed the results of 37 prospective cohort studies of nearly two million (1,950,198) healthy men and women worldwide.

There have been inconsistent findings from observational studies prolonging the controversy over the effects of GI and the risk of lifestyle diseases. 'The key message from this study,' says lead author Alan Barclay, 'is that the GI of your diet is a powerful predictor of disease risk. Grandma was right, you are what you eat.'

'The GI is a physiologically-based ranking that distinguishes how different carbohydrate foods (sugars and starches) affect your blood glucose levels.'

'If you eat carbohydrate foods (sugars or starches) that break down quickly during digestion, the blood glucose response is fast and high - in other words, the glucose in the bloodstream increases rapidly. These foods have the highest GI values.'

'Foods that contain carbohydrate that breaks down slowly during digestion, releasing glucose gradually into the bloodstream, have low GI values.'

'Low GI foods have benefits for everybody - they can keep you feeling full longer, help you achieve and maintain a healthy weight and provide you and your brain with more consistent energy throughout the day. They can also have a major effect on the way the body functions and whether or not you develop health problems.'

'Here's why. If you have constantly high blood glucose and insulin levels due to eating a high GI diet, you may literally "wear out" your pancreas over time and eventually this can lead to pre-diabetes and type 2 diabetes.'

'There's also some good evidence from the studies that have been done that high blood glucose and insulin levels are linked to cancer, as well. This is because constant spikes in blood glucose that cause the body to release more insulin, also increase a related substance called insulin like growth factor one (IGF-1). Both these hormones increase cell growth and decrease cell death, and have been shown to increase the risk of developing cancer.'

'Other research shows that a high GI diet tends to reduce "good" HDL cholesterol levels and raise triglycerides levels; bad news for cardiovascular diseases. And people with low HDL cholesterol and high triglyceride levels are more prone to gall stones.'

So what's the take-home message?

In some respects it's a good news message for individuals and governments,' says Barclay. 'There is a simple, cost-effective way for everybody to reduce their risk of these debilitating chronic diseases and enhance their quality of life - we all need to eat a healthy, low GI diet.'

'How low? We believe we believe that a GI of 45 or less is a reasonable definition of a low GI diet or meal. This is because what we now know from numerous observational cohort studies around the world is that the average GI of the diet of people in the lowest quintile (20% of the population) is about 40-50. Similarly, in a recent meta-analysis of 15 experimental studies investigating the role of low GI diets in managing diabetes, the average GI was 45. Since this average GI has been proven to have significant health benefits in people with existing diabetes and in reducing the risk of chronic diseases like heart disease and diabetes, and importantly, people can and do achieve it in real life, we believe a GI of 45 or less is what we all need to be aiming for.'

'How? Well, it's as easy as 'this for that.' When you are buying bread or breakfast cereal for example, simply choose the one with a lower GI. Look for the GI Symbol or check the GI database: www.glycemicindex.com or the GI newsletter: http://ginews.blogspot.com for the GI of your favourite foods.'

Ten tips for reducing the GI of your diet

- Choose a low GI bread. Look for the GI Symbol or choose a really grainy bread, sourdough bread or soy and linseed bread.

- Replace high GI breakfast flakes that spike blood glucose levels with low GI natural muesli, traditional porridge oats or one of the lower GI processed breakfast cereals.

- If you are a big potato eater, either have one or two Nicola, Almera or tiny chat potatoes or make 'mash' replacing half the potato with cannellini beans.

- Look for lower GI rices such as basmati, Doongara Clever Rice or Moolgiri medium grain rice and choose less processed foods or low GI wholegrains such as rolled oats or quinoa for porridge or pearl barley, buckwheat, bulgur, whole kernel rye, or whole wheat kernels.

- Eat legumes (beans, chickpeas and lentils) often - home cooked or canned.

- Include at least one low GI carb with every meal. You'll find them in four of the food groups: fruit and vegetables; bread and cereals; legumes; low fat dairy or soy alternatives.

- Choose low GI snacks - fresh fruit, a dried fruit and nut mix, low fat milk or yoghurt.