The glycemic index or GI is a rating system for carbs that helps us to choose the right food that not only satisfies our nutritional needs but also protects us from the risks due to diabetes, heart attacks and possibly cancer.
GI ranks food on a scale between 1 and 100 based on how fast they metabolize and affect blood glucose levels. GI measures how fast sugars are released into the bloodstream two or three hours after a meal. Carbohydrates that have higher GIs break down quickly and raise blood glucose to dangerous levels. Carbohydrates with lower GIs break down more slowly, releasing glucose gradually into our blood streams. Food with GI less than 55 are thought of as low glycemic, those between 55 and 70 are thought of as medium, and those greater than 70 are thought of as high, on this scale.
The GI values are useful as guides to food selection for those affected by diabetes. High GI foods such as potatoes, rice, pasta and bread cause a quick rise in blood sugar and insulin levels, and increased insulin levels cause hunger and subsequent weight gain.
A low GI diet can keep metabolic processes and glucose levels in check. This includes brown rice, parboiled rice, barley, bulgur, pasta, whole grain breads, sweet potatoes (not potatoes), dairy products, legumes, dried beans and lentils. Apart from producing low glycemic responses, these food also lower lipid levels in the blood.
High fiber vegetables have low GI. Thus, oatmeal has a lower GI than corn flakes. Generally speaking, the less processed foods are, the lower their GI. That explains why oranges and apples have a lower GI than the juices made out of them. Therefore a diabetic person should go for the less processed item whenever possible.
Low GI foods containing fiber increase the production of short-chain fatty acids, alter bacterial flora in the small bowel and increase colonic fermentation and fecal bulk. This has the benefit of reducing free fatty acids in the blood — a contributory factor for insulin resistance.
Soluble fiber has several major benefits for people with diabetes. They slow the digestion of starches and sugars and reduce blood glucose spikes. They also decrease the cholesterol levels in our blood. Oatmeal, barley and oat bran have soluble fiber. Dried fruit, nuts and seeds have fiber too.
Selecting food merely based on GI wouldn’t always make the best nutritional choice. For example, GI of whole wheat bread is identical to white bread, though the former is still healthier due to the presence of fiber. Similarly, though table sugar has lower GI than potatoes, it has no nutritive value and provides only empty calories. The fructose present in potatoes has to get converted into glucose in the liver, and this delay in processing is why its GI is lower than potatoes which consist chiefly of glucose.
