Glycemic Index

The glycemic index of a food is a measure of the effect of carbohydrate on blood sugar levels. Foods that can be broken down quickly after ingestion to release glucose into the bloodstream are considered to have high GI, while foods that are broken down slowly and release glucose gradually into bloodstream are considered to have a low glycemic index. Those with diabetes , maintaining a diet made up of low GI foods has several important health benefits.

How do you define glycemic index ?

( Two hour blood glucose response of required food ) X 100

Glycemic index of standard food (glucose or white bread)

Glycemic Load

Glycemic load accounts for how much carbohydrates Is present in the food and how much each gram of carbohydrates raises blood glucose levels.

The glycemic load of a food is calculated by multiplying the glycemic index by the amount of carbohydrates in grams provided by a food and dividing the total by 100.Dietary glycemic load is the sum of the glycemic load in all foods consumed in the diet.

There are a variety of factors that can account for the glycemic index of different foods, Some of which are naturally occurring, whereas others are affected in commercialization or home preparation.

Physical form : generally , the more processed a food , the higher the GI , for example instant oatmeal has a GI of 79 whereas steel cut rolled oats has a GI of 55.

Food combinations: when carbohydrates foods are eaten as part of meals the GI of the meal changes based on the average of all the food had (such as red beans or legumes with rice).

Cooking time: longer cooking time may increase the glycemic impact as a food by breaking down the starch or carbohydrate and allowing it to pass through the body more quickly when consumed.

Acidity : the more acidic a food is ( pickled food or those containing vinegar or lemon), the lower GI . for example , sourdough bread , which uses a lactobacillus or lactic acid culture as part of the leavening process, has a lower GI than white bread.

The fibrous coat around beans , seeds and plant cell walls in whole grains acts a physical barrier , slowing access of

digestive enzymes to break down the carbohydrate, thus whole grain and legumes have a lower GI.

Protein/fat: adding protein or fat , which have minimal effects on glycemic

Excursions, to a high GI food will decrease the GI of that food . for example, adding cheese to a slice of bread would decrease the GI.

Soluble fiber: by increasing the viscosity of the intestinal contents , the interaction between the starch and the digestive enzymes is slowed, resulting in slower and lower glycemic excursions .

Eventhough fatty foods such as cheese ,ghee etc are low in GI , these cannot be included in the diet as these are high in calories and fat.

Impact of glycemic index ?

On diabetes: the foods with lower GI enters the gastrointestinal tract at the slower rate, which reduces both the glycemic response and corresponding insulin release thus reducing the risk for post prandial hyperglycemia.

On obesity: decreased calorie intake throughout the day after the consumption of low GI meal

Increased the cholecystokinin (CCK) release [which are partially responsible for the sending satiety signals to the brain, thus helps in weight reduction.]

On Cardiac health: foods with low GI results in lowering LDL cholesterol and improved HDL cholesterol.

Message about glycemic index

Choose more fruits and vegetables.
Increase soluble fibre in diet.
Use combination of high GI foods with low GI foods.
Choose fewer processed foods.

Reference

Glycemic Index and Diabetes -American Diabetes Association IGNOU text book of nutrition

Ideas for ideai diabetic care-karnataka institute of diabetes

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