When it comes to maintaining a healthy diet, the glycaemic index (GI) is a term that often crops up in nutrition related discussions. The glycaemic index is a measure of how quickly carbohydrate-rich foods raise blood sugar levels. Some foods are quickly broken down by the body and lead to a rapid increase in blood sugar levels, while others are slowly digested and cause a more gradual rise in blood sugar. Understanding the glycaemic index can help people make informed food choices and manage conditions such as diabetes.
What is the Glycaemic Index (GI)?
The GI is a measure that indicates how quickly a food that contains carbohydrates can raise blood sugar levels after consumption. It is compared to a reference food, usually glucose or white bread. If a food has a high GI value, it means that it is rapidly digested and absorbed, causing a quick spike in blood sugar levels. However, if a food has a low GI value, it is digested and absorbed slowly, resulting in a gradual and sustained release of glucose into the bloodstream.
Take a look at the graph below. It shows an example of how blood sugar levels change over time. When a person consumes a high GI product, you'll notice that the red line representing their blood sugar levels rises quickly, while the blue line (low GI products) is more spread out over time.
What are the rankings of GI in specific products?
The ranking of the GI goes from 1 up to 100, thus a blood glucose profile of 50 grams of pure glucose is given a GI of 100 in this system.
Foods are classified based on their GI value as follows:
High glycaemic or quick carbohydrates have a GI greater than 70
Moderate GI carbohydrates range from 55 to 70
Low GI carbohydrates have a value of less than 55
Here are some examples of products with their respective GI values:
Low GI
Kidney Beans (Phaseolus vulgaris L.), soaked overnight, boiled, cooled overnight, microwaved, 13 GI
Raw Peach, 28 GI
Spaghetti, boiled 5 min, 35 GI
Banana bread, made with 100% whole wheat flour, 54 GI
Sweet potato (Ipomoea batatas), boiled, 44 GI
Medium GI
Basmati rice, white, boiled, 65 GI
Croissant, 67 GI
Muesli, Apple & Raisin 66 GI
Raw, overripe Banana, 57 GI
Couscous, boiled 5 min, 70 GI
High GI
Chocolate cookie, 78 GI
Pancakes, prepared from wheat flour, 80 GI
Sava potato, peeled, boiled 21-30 min, 78 GI
Raw Watermelon, 80 GI
It is fascinating to note that despite containing simple carbohydrates, fruits usually have a low GI, whereas complex carbohydrate-rich foods like potatoes and rice have a high GI.
Did you know that your food's GI can be influenced from many factors?
There are various factors that affect the glycaemic index (GI) of a food. These factors are:
Soluble fibre: Foods that contain soluble fibre tend to slow down digestion, leading to a lower rise in blood glucose levels. Examples of such foods include beans, lentils, peas, and oats.
Amylose and amylopectin: These are two types of starch that affect digestion speed and consequently the GI. Foods that have a high amylose content, such as beans, lentils, peas, and basmati rice, tend to have a lower GI.
Wheat flour products: These products have a higher amylopectin content, which leads to a higher GI level.
Processing: Foods that undergo processing tend to have smaller particles, leading to a higher GI. Breakfast cereals, for instance, tend to have a higher GI than muesli.
Water: When starch is swollen with water, it leads to faster digestion and a higher GI. Cooked potatoes, for example, have a high GI.
Fat and protein: These macronutrients slow down stomach emptying, leading to a lower GI. Potato chips, for instance, have a lower GI than plain boiled potatoes. Eating chicken with rice or potatoes can also lower the GI.
Sugar content: Sugar is broken down into glucose and fructose, and fructose leads to a slower rise in blood glucose, hence a lower GI.
Why does Glycaemic Index matter?
The impact of food on blood sugar levels is not only a concern for people with diabetes. Even for those without diabetes, understanding glycaemic index can have significant implications for overall health and well-being.
Blood Sugar Regulation: Foods with a high glycaemic index can cause rapid fluctuations in blood sugar levels, followed by a crash which can leave you feeling hungry and fatigued. In contrast, low-GI foods offer a more stable and sustained source of energy, helping to keep blood sugar levels steady and reducing the risk of energy crashes.
Weight Management/Metabolic Syndrome: High-GI foods can trigger hunger and cravings, leading to overeating and weight gain. In contrast, low-GI foods promote satiety and can help control appetite, making it easier to maintain a healthy weight.
Diabetes Management: For people with diabetes, monitoring and managing blood sugar levels is crucial for overall health. Choosing low-GI foods can help stabilize blood sugar levels and reduce the need for insulin or other medications.
Heart Health: Research suggests that diets rich in high-GI foods may increase the risk of heart disease and other cardiovascular issues. In contrast, diets emphasizing low-GI foods have been associated with better heart health outcomes.
What should you do to achieve a lower GI diet?
Eating plenty of fresh fruits, such as apples and oranges.
Opt for low-GI starchy vegetables, such as sweet potatoes and yams.
Low-GI cereals, such as oatmeal and muesli.
Choose low-GI bread, such as those containing barley, rye, oats, sunflower seeds and pumpernickel.
Low-GI grains like wholegrain pasta, oats, buckwheat, quinoa and basmati rice.
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