What is the difference between Glycemic Index and Glycemic Load, and what should I follow? This question came in via email from Mike in Pennsylvania.
While equal justice for all helps to insure a basic promise of a democratic society, in a world of nutrition the same promise does not apply. Those pesky carbohydrates are a rebellious bunch.
Glycemic Index (GI) is a ranking system designed to rank carbohydrates according to their affect on our blood sugar level. The index measures how quickly a fixed food serving (usually 50 g) converts to sugar. Foods with carbohydrates that break down rapidly cause a dramatic rise in blood sugar and insulin levels, because our body needs less energy to convert such foods into sugar.
The Glycemic Index has its critics. The GI of a food could vary depending on a number of factors such as: ripeness, storage time, cooking method, variety, and a food combination in a given meal. There are other individual dependent contributing factors, such as: insulin resistance, blood glucose levels, and glycemic response.
If you want to know the impact of a particular food on blood sugar and insulin, you need to know the glycemic index and how much of that food you are going to eat. GI ranges are:
Low GI = 55 or less
Medium GI = 56-69
High GI = 70 or more
The Glycemic Load (GL) is a more accurate indicator of carbohydrate conversion and its affect on our blood sugar and insulin levels. The GL provides a measure of an overall impact on our blood sugar and insulin level. To calculate it, multiply GI value by the amount of carbohydrate (grams), divided by 100. GL ranges are:
Low GL = 10 or less
Medium GL = 11-19
High GL = 20 or more
To help illustrate all of this a little better, please consider this example.
The GI value for a carrot juice = 43
The GI value for a boiled carrot = 92
The GI value for boiled wholemeal spaghetti = 32
Thus, on a surface it seems like boiled wholemeal spaghetti is a better choice. However, the GL values for the above foods reveal something interesting.
The GL value for a carrot juice = 5.7
The GL value for a boiled carrot = 3.9
The GL value for boiled wholemeal spaghetti = 14.2
Despite the fact that a boiled carrot has a whooping GI of 92, the GL for it is only 3.9.
My recommendation is not to be overly concerned with GI or GL, unless you have a diabetic condition, in which case you should consult with your doctor.
If you are trying to lose weight, increase the consumption of non-starchy vegetables, moderate to low-carb fruits, and do not be a stranger to lean protein sources. Stay away from sugary foods like cakes, candy, soft drinks, cookies, and sources of simple carbohydrates like white bread, white rice, pasta and potatoes.