The glycemic index (GI) is a number that is a measure of how fast a food raises blood glucose. The lower the number, the slower the glucose is raised. Since complex carbs elevate glucose slower than simple carbs, foods that are rich in complex carbs have lower numbers, and are more desirable than food with higher numbers. For example, oatmeal has a GI of 58 (medium) vs Corn Flakes® that has a GI of 81. In addition to be converted into glucose more slowly, oatmeal provides extra nutrients to the body. Simply put, the glycemic index helps identifying food that are more suitable for your diet, especially for Type 2 diabetes, as it is believed that high-glycemic food strain beta cells over time and limit their ability to produce insulin.
The Glycemic Index (GI) can be categorized as low, medium or high:
- Low (GI of 55 or less): most fruits and vegetables, legumes/pulses, whole grains, nuts, fructose and products low in carbohydrates
- Medium (GI between 56 and 69): whole wheat products, basmati rice, sweet potato, sucrose, baked potatoes
- High (GI of 70 and above): white bread, most white rices, corn flakes, extruded breakfast cereals, glucose, maltose
A complete database of glycemic index can be found at http://www.glycemicindex.com/
A quick rule of thumb is that natural food have lower glycemic index than processed food. As an added benefit, natural food provide more nutrients and are healthier than processed food.
The glycemic load takes into account the amount of carbs in the servings. For example, although a candy has a higher glycemic index than brown rice, a single candy contains less carbs than a a cup of brown rice, and has less of an impact on glucose overall. The glycemic load takes into account the glycemic index of a food and its amount of carbs per serving (it’s a mathematical formula: GI x carbs / 100).
Which One Matters?
Some people prefer the glycemic index, because they prefer to consume complex carbs to prevent blood glucose spikes. Others will refer to the glycemic load as they consider the overall impact of the food they eat. It boils down to what works best for each. Generally speaking, favor food with low glycemic index and/or glycemic load, meaning that you will consume food with a more stable effect on your glucose.
An issue with choosing food based on their glycemic index is that it ranks them based on one factor (the elevation of blood glucose), disregarding factors such as how ripped a food is, whether it is processed or prepared, the time of day it is eaten, the other foods consumed with it, etc. all of which can influence how a food is absorbed.