The glycemic index (GI) measures how a carbohydrate-containing food raises blood glucose. Fat and fiber content tend to lower the glycemic index (GI) of a food. As a general rule, the more cooked or processed a food, the higher the GI.
There are several factors that can affect the glycemic index (GI) of a food. These factors include:
- Ripeness and storage time: The more ripe a fruit or vegetable is, the higher the GI.
- Processing: Juice has a higher GI than whole fruit; mashed potato has a higher GI than a whole baked potato, stone ground whole wheat bread has a lower GI than whole wheat bread.
- Cooking method: How long a food is cooked (al dente pasta has a lower GI than soft-cooked pasta).
- Variety: Converted long-grain white rice has a lower GI than brown rice but short-grain white rice has a higher GI than brown rice.
The glycemic index (GI) value represents the type of carbohydrate in a food but says nothing about the amount of carbohydrate typically eaten. Portion sizes are still relevant for managing blood glucose and for losing or maintaining weight. The GI of a food is different when eaten alone than it is when combined with other foods. When eating a high GI food, you can combine it with other low GI foods to balance out the effect on blood glucose levels. Many nutritious foods have a higher GI than foods with little nutritional value. For example, oatmeal has a higher GI than chocolate. Use of the GI needs to be balanced with the basic nutrition principles of variety for healthful foods and moderation of foods with few nutrients.