Glycemic Index and Blood Glucose Level
by MedPlus Team, February 24, 2017
Glycemic Index (GI) is a relative ranking of carbohydrate (Sugar) in foods according to how it affects blood glucose levels. High GI foods tend to be high in simple sugars and can cause a rapid rise in blood sugar levels immediately after consumption, further leading to a rapid rise in insulin levels with adverse effects on health.
Low GI ranking foods are more slowly digested, absorbed, and metabolized and cause a lower and slower rise in blood glucose and, therefore insulin levels. Further, as the body will digest these foods slowly, you will feel full for a long time and you would be eating fewer calories without feeling hungry. This means foods with lower GI are beneficial for weight loss and in decreasing the risk of cardiovascular disease, type 2 diabetes, stroke, depression, formation of gall stones, chronic kidney disease, metabolic syndrome, neural tube defects, formation of uterine fibroid, and cancer of breast, colon, prostate, and pancreas.
How is Glycemic Index given to a particular food?
The Glycemic Index is a value obtained by monitoring a person’s blood sugar serially at fixed intervals after eating the food. Initially, 10 or more healthy people are given a quantity of food to be tested containing 50 grams of carbohydrate and their blood glucose levels are checked over the next two hours. For each person, the incremental area under their two-hour blood glucose response (glucose iAUC) for this food is then measured. On another occasion, the same 10 people consume an equal-carbohydrate portion of plain glucose sugar (the reference food) and their two-hour blood glucose response is also measured. A GI value for the test food is then calculated for each person by dividing their glucose iAUC for the test food by their glucose iAUC for the reference food. The final GI value for the test food is the average GI value for the 10 people.
The Glycemic Index range is as follows:
Very Low or Low GI =55 or less;
Medium GI = 56-69;
High GI = 70 or more.
Making a healthy choice:
Exchange high GI foods for low GI foods and eat at least one serving of a low GI carbohydrate food at each meal. Keep a watch on the serving size as eating too much food, even if it is a healthy choice, is not all that good.
You don’t need to completely cut out high GI options – the trick is to combine them with low GI options to get to a moderate GI. Certain acids have been proven to lower the GI of certain foods. A few examples can be to add vinegar on salads, yogurt with cereal and lemon or lime juice on vegetables. How you cook them also has an impact on the Glycemic Index given to a particular food