The glycemic index works best when it is combined with the second concept for predicting the glycemic effect of your total carbohydrate intake, known as glycemic load (GL). GL takes into account both the GI value and the quantity of carbohydrates that you eat. A GL of 20 or more is “high,” 11 to 19 is “medium,” and 10 or less is “low.” Foods that have a low GL almost always have a lower GI value, with some exceptions: watermelon has a high GI value (72), but the carbohydrate content per serving of this fruit is minimal, making its GL (4) low (but you do have to watch how big of a piece you eat, since a serving is just over a cup); popcorn also has a higher GI value (72), but it takes a lot to equal 50 grams, which has a GL of just 8.
A careful consideration of the GL of foods is crucial if you want to prevent type 2 diabetes. Several large-scale studies have now confirmed that eating a high-GL diet over the course of years substantially increases your risk for developing diabetes. In other words, overloading with “white” carbohydrates may actually contribute to its onset. Paying attention to your GL is even more important once you have diabetes, when you’re attempting to achieve good control of your blood sugar levels. New research has also shown that eating a low-GL, high-fiber diet raises circulating levels of adiponectin, an anti-inflammatory hormone released by fat cells. If you have diabetes, higher levels of adiponectin in your system will lead to improved insulin sensitivity, reduced inflammation, and better diabetes control.
Unfortunately, you can’t always believe what you read when it comes to the GL of processed foods. Despite what many food manufacturers would like you to believe with their “net carbs,” “carb smart,” and other misleading marketing claims that make foods like high-GL pasta appear to be almost carbohydrate free, the total amount of carbohydrate that you eat, particularly in a high-GL food, can’t be discounted simply because of it has a lower GI value. Slowly absorbed carbohydrates, such as those found in pasta, are still metabolized and contribute to your carbohydrate and calorie intakes for the day. I’ve seen packages of pasta that claim to have “only 5 net carbs” per serving, giving you the impression that you would only be eating 5 total grams of carbohydrate; in fact, the food label revealed that it actually contains 42 grams of carbohydrate per serving and only 2 grams of fiber.
Accordingly, despite the fact that most pasta has a lower GI value, if you eat more than half a cup of it (equal to one serving, which is a lot less than anyone usually eats at a time), the large carbohydrate load will still have a pronounced glycemic effect, and your sugars may rise excessively. Read food labels carefully, though, as some companies have decreased the carbohydrate content of their pastas by adding in extra fiber–which you can determine by looking up the fiber content on the label. The grams of fiber are not absorbed and can be subtracted from the total carbohydrates listed for the product to determine its actual carbohydrate load (which will be affecting your insulin needs and BG levels).
Come back next week for more discussion about GL and GI.