If you’ve never heard of the glycemic index and glycemic load, then this article is going to forever change your relationship with the carbohydrate containing foods you eat… in a good way!
This impacts general health, weight management, and type 2 diabetes.
Before I get into it, I want you to understand that you don’t have to know the exact values to benefit from this. Just a basic understanding will most likely shift many of your daily food choices, and that can make all the difference.
I don’t know about you, but I need at least a little “why” before I’m willing to put any effort in.
Insulin is a master metabolic hormone whose main job is to keep our blood sugar levels in a safe range, but it does so much more. It also has a lot of say in whether we are burning fat or making fat… and whether we are breaking down cholesterol or producing it.
When we eat carbs, our blood sugar levels increase. An appropriate amount of insulin is released to bring our levels down to normal. A small blood sugar spike requires a small amount of insulin, and a large spike requires a lot of insulin.
Keeping our insulin in check is the key. Not only will insulin increase fat and cholesterol production, but chronic overproduction of insulin can, and often does, lead to insulin resistance.
So when it comes to carbs, we need to know 2 things: the amount of carbs and the affect those carbs have on our blood sugar levels (AKA insulin levels). The glycemic load gives us all that information in 1 nice little number.
To understand the glycemic load, we need to first look at the glycemic index. Scientists wanted to know how different foods affected our blood sugar levels. This was particularly important for diabetics, since it was apparent that 10 grams of carbs from one food had a different effect than 10 grams of carbs from another food. In 1981 the glycemic index was born, and since then thousands have foods have been measured.
Here’s what they do. They have 10 healthy folks fast overnight, and then they have them eat the test food. Blood sugar levels are measured over the next two hours, much like the glucose tolerance test we talked about. Finally, they compare the results to eating the same amount of carbs from pure glucose, and after some scientific math, a number is assigned.
It’s important to note that the carb count has to be the same. Meaning if they are looking at 20 grams of carbs from carrots, then they are going to compare that to 20 grams of glucose.
Since the index is based off of glucose, glucose is assigned a number of 100. Foods with a glycemic index of 70 or more are considered high, 56 to 69 are medium, and 55 or less are low.
Now we know how the carbs in each food affect our blood sugar levels… isn’t that great? You bet it is, but it’s only half the picture. If every serving of food had 30 grams of carbs, then we the glycemic index would be enough. The glycemic load takes the glycemic index and factors in the number of carbs per serving. This makes the glycemic load a much more useful number. Foods with a glycemic load of 20 or more are considered high, 11 to 19 are medium, and 10 or less are low.
Let me give you an example. Both watermelon and white rice have a glycemic index value of about 72… that’s HIGH. However, there are not a lot of carbs in a serving of watermelon since it’s mostly water, but there are a lot of carbs in rice. The glycemic load for white rice is about 30 (very high), where watermelon is about 4 (nice and low)!
Warning… Math: Glycemic Load = Glycemic Index/100*Carbs per Serving
Important note: If you eat 2 servings, then you of course double the load. Coke has a glycemic load of about 16 per 8 ounces. Who drinks 8 ounces? A 24 ounce bottle would have a glycemic load of 48.
This is all so interesting, but now what?
Now, go look at the foods you eat on a regular basis and see if you can make some better choices. I promise that you’ll be surprised… some foods you thought were great, might not be so great, and some foods you thought were terrible, might not be so bad. Here’s a list.
Can you tell me why the glycemic load of brown rice is lower than white rice (21 vs 30). Or why a baked potato with the skin is lower than without (19 vs 26)? Hint… it’s the fiber.
photo by iamrenny (flickr creative commons)