GI - Glycemic Index of Foods
A low GI food will release energy slowly and steadily and is generally appropriate for everyone, especially diabetics, dieters and endurance athletes. A high GI food will provide a rapid rise in blood sugar levels and is suitable for energy recovery after endurance exercise.
The glycemic effect of foods depends on a number of factors such as the type of starch (amylose vs amylopectin), physical entrapment of the starch molecules within the food, fat content of the food and increased acidity of the meal - adding vinegar for example, will lower the GI. The presence of fat or dietary fibre can inhibit carbohydrate absorption, thus lowering the GI. Unrefined breads with higher amounts of fibre generally have a lower GI value than white breads, but, while adding butter or oil will lower the GI of bread, the GI ranking does not change. That is, with or without additions, there is still a higher blood glucose curve after white bread than after a low GI bread such as pumpernickel. Many brown breads, however, are treated with enzymes to soften the crust, which makes the starch more accessible. This raises the GI, with some brown breads even having GI values over 100.
The glycemic index can only be applied to foods with a reasonable carbohydrate content, as the test relies on subjects consuming enough of the test food to yield about 50 g of available carbohydrate. High fat or high protein foods such as meat, eggs, nuts and cheese have a negligible GI. Furthermore, many fruits and vegetables (but not potatoes) contain very little carbohydrate per serving, and also have very low GI values. This also applies to carrots, which were originally and incorrectly reported as having a high GI [2]. Alcoholic beverages have been reported to have low GI values, however it should be noted that beer has a moderate GI. Recent studies have shown that the consumption of an alcoholic drink prior to a meal reduces the GI of the meal by approximately 15%[3].
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