VIEWPOINTS FROM THE CHARLES PERKINS CENTRE, SYDNEY UNIVERSITY
YOGHURT IS A LOW GI FOOD
The Sydney University GI Research Service (SUGiRS), established in 1995 to provide a reliable commercial GI testing laboratory, has tested a variety of yoghurts over the past 20 years – plain, flavoured, full fat, and diet. Over the same period of time, numerous studies in peer-reviewed journals have shown that high yoghurt intake is associated with a reduced risk of type 2 diabetes. Although several mechanisms could explain this association, Prof Tom Wolever recently addressed the glycemic and insulinemic impact of yoghurt in Nutrition Today.
“There is evidence that low GI and low GL (glycemic load) diets are associated with a reduced risk of type 2 diabetes. The 93 GI values for yoghurt in the University of Sydney’s GI database have an average of 34 and most (9 out of 10) of the yoghurts are low GI. The 43 plain yoghurts in the database have a lower GI (average GI = 27) than the 50 sweetened yoghurts (average GI = 41). This difference is not explained by sugar, per se, but rather by the higher protein-to-carbohydrate ratio in plain yoghurt. Although yoghurt has a low GI, its insulinemic index is higher than its GI. High insulin responses may be deleterious because hyperinsulinemia is associated with an increased risk of type 2 diabetes. Nevertheless, this may not be a concern for yoghurt because, although its insulinemic index is higher than its GI, the insulinemic index of yoghurt is within the range of insulinemic index values for non-dairy low-GI foods. In addition, mixed meals containing dairy protein elicit insulin responses similar to those elicited by mixed meals of similar composition containing non-dairy protein. Because the GI of yoghurt is lower than that of most other carbohydrate foods, exchanging yoghurt for other protein and carbohydrate sources can reduce the GI and GL of the diet, and is in line with recommended dietary patterns, which include whole grains, fruits, vegetables, nuts, legumes, fish, vegetable oils, and yoghurt.”
What’s the Insulinemic Index? Prof Jennie Brand-Miller explained this recently.
“One of insulin’s many functions is to act as a growth hormone designed to drive nutrients into cells – not just glucose but also amino acids, the building blocks of new tissue. When we eat carb-rich foods our blood glucose levels rise and our pancreas then releases insulin (a hormone) that drives the glucose out of our bloodstream and into our body’s cells where our body can use it as an immediate source of energy or store it as glycogen. What many people don’t realise is that protein foods (meat, fish, eggs and dairy foods) also stimulate insulin secretion – that’s why you may see them described as insulinogenic.”
Scientists at the University of Sydney have been researching the food insulin index or FII for more than 20 years. “The FII looks at how much insulin the body normally releases in response to a whole food or meal (its carbohydrate and the quantity and quality of its protein and fat). Some foods need more insulin to help utilise them, while other foods need much less. Choosing foods with a lower FII can help reduce your overall insulin demand on your pancreas or insulin requirements,” says dietitian and diabetes educator Dr Kirstie Bell.