Why would one high-carb food have a different GL than another? Why does white rice, for instance, have a higher GL than, say, honey? It has to do with the way nature constructed them. Carbohydrates consist of starches and sugars. Starch — think of starchy foods like beans and potatoes — is made up of sugar molecules bound together in long chains. When you eat a carbohydrate- rich food, your body converts those starches and sugars into glucose, or blood sugar.
Some starches, like those in white rice, are extremely easy for the body to convert, and therefore blood sugar levels rise like a hot temper after you eat them. Others, like those in beans, take a lot more work to break down, so blood sugar levels simmer rather than explode.
Four factors determine how fast the body breaks down carbohydrate.
The Type of Starch — or Why to Avoid Sticky Rice
Remember, starches are made of sugar molecules chained together. Some chains have straight edges, while others are branched. The straightedged type, called amylose, is harder for your body to break down and turn into blood sugar. The branched type, called amylopectin, is much easier to break down because there are so many places for the enzymes that break down starch to get at it. Think of a tree with lots of branches — there are a lot more spots for birds to land on it compared to a simple post.
White potatoes are very high in amylopectin, the branched kind of sugar chain, which is why they raise your blood sugar in a jiffy. Peas and lentils are high in amylose, the straight kind, so they’re converted to blood sugar at a snail’s pace. The more amylose a food contains, the slower it will be digested and converted into blood sugar. Take rice, for instance. Some types contain more amylose than others. In general, the softer and stickier the rice is after cooking, the lower its amylose content; this is why “sticky rice” is dastardly to your blood sugar. The firmer the rice, the higher the amylose and the harder it is for your body to turn into blood sugar quickly — making brown rice a better choice. Some genetic variants of rice — such as some sold in Australia, for example — are particularly high in amylose (as much as 25 percent), but unfortunately, most of the rice we eat is low in amylose and thus has a high GL.