There’s a misconception that all sugars have a high GI. The GI of sugar ranges from as low as 23 for fructose to up to 105 for maltose. Therefore, the GI of a food partly depends on the type of sugar it contains. For example, fruits like kiwi, apple, guava, pear, plum, peach, papaya have low to medium glycemic index and banana, sapota, mango, white rice, white flour have high glycemic index.

Starch is a carbohydrate comprising two molecules — amylose and amylopectin. Amylose is difficult to digest, whereas amylopectin is easily digested. Foods with higher amylose content will have a lower GI. Example- Oats, beans, lentils, quinoa have high amylose content.

Processing methods such as grinding and rolling disrupt amylose and amylopectin molecules, raising the GI. Generally speaking, the more processeda food is, the higher its GI. Example- cornflakes have high glycemic index.

Adding protein or fat to a meal can slow digestion and help reduce the glycemic response to a meal.

Protein & Fat slow down the rate of stomach emptying and carbohydrate digestion – e.g foods that contain protein and fat such as milk and legumes have a low GI. Well-balanced mixed meal have low GI value if contains protein-rich food.

Soluble fibre slow down interaction between starch and enzymes.e.g High fibre foods such as rolled oats ,beans, lentils, sprouts have low GI.

When food is processed or cooked the structure of the starch changes and the granules become swollen (Gelatinized). For example germination of grains reduces GI value.

The acid in foods slows down the rate of digestion and absorption. The addition of lemon juice, and vinegar reduces GI.

The more fats or acid a carbohydrate food contains, (or, the more fats or acid in the stomach, during digestion) the slower the carbohydrate food is converted to glucose and absorbed into the bloodstream. The presence of fat and/or acid retards the emptying of the stomach. For example: adding vinegar, lemon juice, and pickles, will help to lower the GI of a meal.

Preparation and cooking techniques can affect the GI too. Generally, the longer a food is cooked, the faster its sugars will be digested and absorbed, raising the GI.

Unripe fruit contains complex carbs that break down into sugars as the fruit ripens. The riper the fruit, the higher its GI. For example, an unripe banana has a GI of 30, whereas an overripe banana has a GI of 48.

The degree of ripeness as well as the way that certain foods are cooked and prepared can affect the GI of the final product.