What is GI? 

GI is defined as a relative ranking of carbohydrates in foods according to how they affect blood glucose levels.

Carbohydrates with a low GI value (55 or less) are more slowly digested, absorbed and metabolized and cause a lower and slower rise in blood glucose and, therefore insulin levels. For better blood sugar control, select low or medium GI food options over high GI food items. 

Do note that the GI of a food is different when eaten alone than it is when combined with other foods. Thus when eating a high GI food, you can combine it with other low GI foods to balance out the effect on blood glucose levels

What determines GI? 

1) How processed is your food
The method of processing a single food can significantly affect its GI, and processed food tends to have a higher GI. For example, white flour (GI 69), which is refined, has a higher GI than whole wheat grains (GI 42). This is because grinding breaks the grain’s protective layers, thus making digestion and absorption easier. Similarly, fresh fruit juices will have a higher GI than whole fruits - orange juice has a GI of 46 while orange has a GI of 40. In addition, finely ground grain is more rapidly digested than coarsely ground grain. For example, instant oats cereal porridge (GI 65) has a higher GI than rolled oats porridge (GI 42).

2) Is your food overcooked?
The cooking method can make a huge difference to the food's GI as cooking breaks down the cellular structure of the food, making it easier to digest and raising blood glucose levels. Overcooking will boost the GI. For example, porridge has a higher GI than plain rice (83 vs. 69), soft-cooked pasta has a higher GI than al dente pasta (58 vs. 43), and mashed potato has a higher GI than a whole baked potato (73 vs. 60). Overcooking pasta, for instance, contributes to starch gelatinization, which then raises the GI.  High heat cooking methods like baking or frying will raise GI compared to lower heat methods like sautéing (cooking them quickly in a bit of fat) or parboiling (partially cooking them in boiling liquid). For example, baked or deep frying potatoes will cause GI to increase to 83 and 70, while boiling it achieves a GI of 59.

3) Does your carbohydrate meal contain other ingredients such as fat, fibers, or protein?
Adding fat, fiber, or protein to food can help slow carbohydrate digestion and absorption, lowering GI. For instance, instant mashed potato consumed on its own has a GI of 88, while instant mashed potato consumed with butter and cheese has a GI of 66. Similarly, keeping the potato’s skin on adds fiber and lowers GI. For example, a baked skinless white potato has a GI of 98, and a potato with skin kept on has a GI of 69. However, it is essential to note that not all high fiber foods are low in GI because fiber can be classified as soluble and insoluble fiber. The presence of soluble fibers, which are viscous, slows down digestion, and food with more soluble fiber tends to be lower in GI. On the other hand, insoluble fibers are not viscous and do not help slow digestion. Thus, food high in insoluble fibers tend to be higher in GI.

Impact of GI on blood glucose and weight

For those with diabetes, a low-GI diet can help them better manage their blood glucose levels to minimize peaks and manage hunger to support or facilitate weight loss. However, while GI can be a helpful reference for meal planning, it should not be the only consideration. Both the serving size of foods and the nutritional quality of the diet is just as important to consider.  

Here are some tips to start adopting a low-GI diet:

1. Snack smart
Instead of munching on cupcakes or chips, opt for nuts. When it comes to fresh fruits, get to know the GI of your favorites as the data may surprise you. There are some fruits with moderate GI white other fruits can deliver a much higher GI value. For example, the GI of watermelon is 80 while the GI of apple is 40.

2. Keep things moderate

No matter how low the GI of your carbohydrate choice, overeating is never healthy, and moderation is still the key. Refer to plate method to learn more about the various food groups and their recommended portions. Staying close to the portion guidance will also help you moderate your blood sugar swings.

Your smart choice

For people with diabetes, low GI foods are highly recommended, so kick-start your low GI diet today! It can help to maintain your blood glucose level and avoid potential health complications in the long run. A low-GI diet may also help to prevent obesity. If convenience is a priority, consider a diabetes-specific formula as one of your low GI food options. Such formulas are specially designed for people with diabetes to help manage blood sugar levels when used as a meal replacement, part of a meal, or as a snack in a well-balanced and individualized diet. At the same time, it is designed to provide complete and balanced nutrition. They taste delicious too! Consult your doctor or dietitian to find out how you can incorporate a diabetes-specific formula into your meal plan. 

Carroll et al. J Clin Endocrinol Metab.2003; 88:5248-5254

Monnier L et al. Diabetes Care. 2002;25:737-41

GI Source: <Reference for GI values of the foods mentioned in the article>

• University of Sydney

• The American Journal of Clinical Nutrition’s International table of glycemic index and glycemic load Values