Dr Alan Barclay
Families share more than their genes
As we describe in food for thought this issue, the road to type 2 diabetes can run in the family. One of the main reasons is genetic – you are genetically very similar to your biological parents and siblings. Your height, amount of muscle, the size of your essential organs and amount and location of your body fat is partially determined by your genes, and this in turn affects your insulin sensitivity, amongst many other things.
We tend to overlook, or perhaps downplay, the role of the family environment in the expression of those diabetes genes. As well as inheriting genes, we tend to inherit a “lifestyle”. If your parents were always active and encouraged you to participate in team sports, bicycle riding, walking, dancing, etc., chances are they and you will have reduced the risk of developing type 2 diabetes, as you will all have more muscle, a lower amount of body fat and less insulin resistance than if your lifestyle was a sedentary one.
We also inherit eating habits. Our family background is a powerful predictor of our family’s diet. It’s well established that type 2 diabetes is more common among certain groups including people from the Middle East, South Europe, South Asia, Indigenous Australians, Maoris, Pacific Islanders, African Americans, Hispanic Americans and American Indians compared with people from an Anglo-Celtic background, for example. Again, along with their genes, they inherited their ancestors’ eating patterns built around their traditional foods and drinks and ways of preparing and eating foods. These dietary and cultural patterns undoubtedly influence the expression of diabetes genes.
There is strong evidence that both the traditional Mediterranean diet and certain traditional Asian cuisines like traditional Japanese diets are associated with longevity and a lower risk of developing chronic diseases like type 2 diabetes, despite being composed of very different foods, with very different macronutrient profiles – Mediterranean diets are relatively high in fat whereas most Asian diets are very high in carbohydrate and low in fat. What these traditional eating patterns have in common, however, as discussed in What’s New in this issue is that they were built around naturally low GI, minimally processed whole foods.
Of course, that was then. Nowadays, like the rest of us, people living in Asia and around the Mediterranean are adopting more typical Western diets with more refined and processed foods. Indeed, a large population-based study carried out in Western European found that the average GI of the typical Greek diet was 57, whereas in Japan the average dietary GI was 64. A low GI diet has an average GI ≤ 45, so the typical diets of both countries now fall well outside the low GI category and may explain in part each nation’s rising diabetes prevalence rates.
Dietary modelling conducted at the University of Sydney showed that by simply swapping medium to high GI foods with lower GI equivalents in modern Asian and Greek cuisines, you can reduce average dietary GI down to the recommended range. This simple “swap it don’t stop it” approach is one way of improving dietary quality, and it works with a range of cuisines, meaning people can continue to enjoy the foods they love, and it doesn’t have to ruin their social or cultural life. This is one reason why low GI diets are sustainable in the long-term.
So, even if you have a strong family history of type 2 diabetes, don’t think that it is inevitable that you and your children will develop it. Be an active family and use the “swap it don’t stop it” approach to improve your eating habits. This long term recipe for success will help you prevent, or at the very least delay, the onset of type 2 diabetes.
GI Symbol Program
Dr Alan W Barclay PhD,
Chief Scientific Officer,
Glycemic Index Foundation (Ltd):
Sydney University Glycemic Index Research Service: