In the mid-1980s, David Jenkins and Thomas Wolever, who are researchers at the University of Toronto developed the Glycemic Index (GI) as a tool for helping diabetics control their blood sugar levels. Fast forward today, the Glycemic Index (GI) is widely used in sports performance and weight management and as a barometer for evaluating health.
The Glycemic Index (GI) is a numerical index, using a scale of 1 to 100 that ranks carbohydrate-based foods on their immediate effect on blood glucose (blood sugar) levels i.e. by the degree they elevate blood glucose and insulin levels after eating 50 grams of carbohydrates as compared to glucose. Carbohydrates that breaks down quickly has a high Glycemic Index (GI) score (70 above) which tend to increase blood glucose and insulin levels quickly. The lower the Glycemic Index (GI) number (55 or under), the slower the absorption rate, keeping these levels more steady.
Glycemic Index (GI) score is based on a 50gram carbohydrate portion, such as 1¼ cups of rice and 2 medium size apples. The degree to which blood glucose rises after eating the food in question is compared to that seen after eating 50 grams of table sugar, which is given the Glycemic Index (GI) score of 100. It is the difference between the two levels that determines the food’s ranking.
Oatmeal, for example, has a Glycemic Index (GI) of 49, which means oatmeal produces a 49% increase in blood glucose compared straight glucose (which can causes a 100% increase). Food that score above 70 are classified as high glycemic. Food that rate below 55 are classified as low glycemic.
Scientists conclude that the most important factor in predicting Glycemic Index (GI) ranges is the surface area of the food. The more finely a food is ground or the more refined a food is, the higher its Glycemic Index (GI) rating because grinding increases a food’s surface area. Foods with a small surface area typically have a low Glycemic Index (GI).
That said, many researchers point out that the Glycemic Index (GI) is an oversimplification of the way we evaluate bad or good carbohydrates. This is because of how we prepare food, the volume consumed, whether salt or oil is used (in food preparation) and the combination of food we eat all influence our glycemic index. For example, rice cakes are usually assigned a glycemic index of 78 to 82, thus making them a high Glycemic Index (GI) rated food. However, if we add a thin spread of any types of nut butter (such as peanut or almond), that oil content from the butter helps drop the Glycemic Index (GI) score to the 50s range!
By itself Glycemic Index (GI) does not tell us about the carbohydrate content – we need to understand various type of food’s impact on blood sugar and this is essentially where Glycemic Load (GL) comes in. The Glycemic Load (GL) takes in account both rate of release i.e. Glycemic Index (GI) and the actual amount of carbohydrate in a particular food. Hence, Glycemic Load (GL) combines both the quality and quantity of a carbohydrate in a single number.
How Glycemic Load (GL) Calculated?
Glycemic Load (GL) is calculated by multiplying the Glycemic Index (GI) by the amount of carbohydrate in grams provided by a particular food and dividing the total by 100. A high Glycemic Load (GL) carbohydrate has a value of 20 or more, a medium 11 to 9 and a low Glycemic Load (GL), 10 and below.
Although both the Glycemic Index (GI) and Glycemic Load (GL) offer valuable information on how carbohydrates influence blood glucose levels, it is opined that the Glycemic Load (GL) is more practical because it looks at the total carbohydrate load as opposed to single values.
At a glance these indexes and numbers may seem overwhelming and has even been criticised (for oversimplicity) but the benefit of the glycemic classifications have helped draw attention to the fact that refined (and even some unrefined) flours can elevate blood sugar and frequently result in fatique, sweet cravings, excess acidity and others.
The importance of including whole complex carbohydrates (example : brown rice, barley, oats, quinoa) into the daily diet, instead of only refined grain products, has been one of the most valuable benefits of Glycemic Index (GI) research.
More importantly, the Glycemic Index (GI) and Glycemic Load (GL) concept made it easy to assist people with weight problems by reducing their consumption of refined or highly processed carbohydrate while encouraging them to eat more carbohydrate food groups from a wide variety of colourful vegetables and fruits which are full of vitmains, minerals, fibre, antioxidants, enzymes and phytochemicals.