Why is the GI of Frosties (55) lower than Kellogg’s Corn Flakes (77), Crunchy Nut Corn Flakes (72) and Skippy Cornflakes (93)?
Many people assume that the higher the sugar content, the higher the GI. But in fact, starch in cornflakes is very rapidly digested and absorbed (it's been fully 'gelatinised' during processing), giving the product its high GI. When you incorporate sugar into the recipe, you reduce the GI for two reasons:
Both effects work together to give Frosties its lower GI. And by the way, there is absolutely no difference in calories or nutrient content of Frosties vs cornflakes. Processed starch is pretty empty of micronutrients, just like sugar.
- Sucrose has a lower GI than the starch in cornflakes.
- The presence of sugar reduces the ability of the starch to gelatinise by tying up water molecules.
So what you are saying is that even though Frosties has a much lower GI than cornflakes, there would be no benefits in eating the one with the lower GI? I thought that the lower GI was what I was supposed to look for when choosing breakfast cereals
When choosing foods the GI isn't meant to be used on its own. The nutritional benefits of foods are many and varied and that's why we suggest you base your food choices on the overall nutritional content along with the amount of saturated fat, fibre, salt and of course the GI value. So although Frosties have a lower GI, nutritionally they are much the same as cornflakes. However, they won’t spike your blood glucose in quite the same way as cornflakes will, so would be a better choice for sustained energy. But better still, opt for a nutrient-rich, low GI breakfast cereal such as wholegrain oats, muesli or a high-fibre breakfast biscuit.