Unless you are actively treating diabetes with diet, you probably have not paid much attention to the terms 'glycemic index' and 'glycemic load.' They are a couple of terms dietitians and nutritionists toss out, but most people don't really know what they mean. It turns out, they're important terms that can help you in your quest for healthy eating.
The first thing you need to understand is that when your body processes carbohydrates, it turns them into glucose, which is sent to your cells for energy. When there is too much glucose in your blood, your pancreas makes insulin to help process that extra glucose. When you produce too much insulin on a regular basis it leads to insulin resistance, and then to Type 2 Diabetes. The key for good health is to make sure that the glucose enters your blood at a slow, steady rate. You want to avoid large amounts of sugar hitting the blood stream at once, which is referred to as a sugar spike.
This is where glycemic index and glycemic load come in.
The glycemic index (GI) is a measure of how fast carbohydrates are released as glucose into your blood stream. because the goal is to control the sugar in your blood, it makes sense that you should look for foods lower on the GI. You can find a chart listing the glycemic index and glycemic load of many popular foods here.
For reference, a low GI food is one that is 55 or less on the scale. A high GI food is one that is 70 or more. Higher fiber foods tend to have a lower GI, because fiber slows the absorption rate of the glucose.
The glycemic load (GL) measures the amount of carbs in a portion of food. A low GL food is one that is less than 10, and i high GL food is more greater than 20.
Which one should you choose?
Here's where it can get a little confusing. Although you're told to choose lower ranked GI foods, many feel that the GI rating process doesn't give an accurate picture of the health qualities of the food. When the GI is calculated, portion sizes are not figured in,where portion size is a factor in determining the GL of a food.
For instance, watermelon has a GI of 71, which is high, but a GL of only 7.21, which is low. So is watermelon safe to eat? The glycemic index indicates that you should steer away from it, but the glycemic load says that it's safe. And that's the problem.
When calculating the GI for watermelon it was based on a 5-cup serving. However, a typical serving size is only 1 cup. What that means is, the carbs in watermelon are quickly converted to glucose, which is why the GI is high, but, for a standard portion the amount of carbs is relatively low, as indicated by the low GL score
Most experts agree that the glycemic load is a much better indicator of how the food will affect your blood sugar. That being said, foods that rank well on both scales are preferable.