What Are the Six Factors That Affect the GI of Carbohydrates?

The glycemic index or GI value of foods is a useful tool to planning a diet around carbohydrate metabolism in the body. GI value is determined using digestive characteristics of certain foods that contribute to the release rate of glucose into the bloodstream. Carbohydrates that result in a rapid release of glucose have a high GI value, while those with an inhibited glucose release rate have lower GI values.

Physical Structure

• Physical structure is one of the six main factors contributing to the glycemic index of carbohydrates. Smaller particle sizes such as finely ground flour have a higher GI value as they provide ideal surface area for the attack or metabolization of bread by digestive enzymes. In contrast, larger food particles make for a slower attack from digestive enzymes, earning a lower GI value. Carbohydrates that are swollen, like those in soft, white breads, convert to glucose much faster than those that are more condensed, as in rye breads. Carbs that are in beans, nuts, seeds and vegetables have a fibrous surrounding that helps protect from the onslaught from digestive enzymes, earning a lower GI value.

Cooking GI Value

• Food cooked for longer periods of time generally earn higher GI values as digestive enzymes face tougher carbohydrate structures from less cooked foods. Heat changes the physical structure carbohydrates and creates less resistance against enzymes to break them down. Starch is resistant to digestion in its raw form. When cooked, the molecule becomes readily digestible but has potential to regain its resistance after cooling.

Molecular Structure

• Monosaccharides are of the simplest carbohydrate structures. Simpler carbohydrates have higher GI values as they are metabolized at a much faster rate than complex polysaccharides. Starch can affect the GI value of carbohydrates by complicating their chemical structure. There are two types of starches. One being more compact in molecular structure, and the other more stretched out and easier to break down for digestive enzymes. Carbohydrates in beans or lentils, with a higher ratio of tightly packed starches to the extended structured starches, will have lower GI values.

Fiber

• Fiber acts as a protective entity from the attack of digestive enzymes. Introducing a high fiber dish to your meal will lower the GI value and inhibit the rapid breakdown of carbs to glucose in the gut and small intestine.

Fats and Sugars

• Fats contribute to lower the GI value of food by slowing the emptying out of the stomach into the intestine. This prolongs the metabolism of carbohydrates into glucose. Because of their fat content, candy bars are a strange exception to the rule that simple physical structures allow for more rapid conversion to glucose. Sugars inhibit activity from digestive enzymes in the intestine and stomach by stealing away water resources that are necessary to glucose metabolism.