What is the Glycemic Index?
The glycemic index (or GI) is a ranking of carbohydrates on a scale from 0 to 100 according to the extent to which they raise blood sugar (glucose) levels after eating.
Two main hormones from your pancreas help regulate glucose in your bloodstream. The hormone insulin moves glucose from your blood into your cells. The hormone glucagon helps release glucose stored in your liver when your blood sugar (blood glucose) level is low. This process helps keep your body fueled and ensures a natural balance in blood glucose.
Foods with a high GI are those which are rapidly digested, absorbed and metabolised and result in marked fluctuations in blood sugar levels.
Several factors influence the glycemic index of a food, including nutrient composition, cooking method, ripeness, and amount of processing it has undergone.
roasting and baking can break down resistant starch — a type of starch that resists digestion and is commonly found in foods like legumes, potatoes, and oats — thus increasing the GI.
Foods low on the glycemic index (GI) scale tend to release glucose slowly and steadily. Foods high on the glycemic index release glucose rapidly, while boiling is thought to help retain more of the resistant starch and lead to a lower GI, compared with other cooking methods.
as mentioned, ripeness matters a lot, bananas that are fully ripened have a GI of 51, whereas under-ripe bananas have a GI of just 30.
fibre is also one big factor as well when it comes to determining GI of a food. wholegrains and high-fibre foods act as a physical barrier that slows down the absorption of carbohydrate. This is not the same as ‘wholemeal’, where, even though the whole of the grain is included, it has been ground up instead of left whole. For example, some mixed grain breads that include wholegrains have a lower GI than wholemeal or white bread.
One theory about the effect of a low-GI diet is appetite control. The thinking is that high-GI food causes a rapid increase in blood glucose, a rapid insulin response and a subsequent rapid return to feeling hungry. Low-GI foods would, in turn, delay feelings of hunger. Clinical investigations of this theory have produced mixed results.
Also, if a low-GI diet suppresses appetite, the long-term effect should be that such a diet would result over the long term in people choosing to eat less and better manage their weight. The long-term clinical research does not, however, demonstrate this effect.
GI ratings: Low: 55 or less; Medium: 56–69; High: 70 or above;
Low GI carbohydrates is one of the secrets to long-term health, reducing your risk of type 2 diabetes and heart disease. It is also one of the keys to maintaining weight loss.
the GI value of a food is determined by feeding 10 or more healthy people a portion of the food containing 50 grams of digestible (available) carbohydrate and then measuring the effect on their blood glucose levels over the next two hours.
Long-distance runners would tend to favor foods high on the glycemic index, while people with pre- or full-blown diabetes would need to concentrate on low GI foods.
Keep in mind that the glycemic index is different from the glycemic load (GL).
Unlike the GI, which doesn’t take into account the amount of food eaten, the GL factors in the number of carbs in a serving of a food to determine how it may affect blood sugar levels
is glycemic index important for fitness and health?
using the glycaemic index to decide whether foods or combinations of foods are healthy can be misleading.
Foods with a high GI are not necessarily unhealthy and not all foods with a low GI are healthy. For example, watermelon and parsnips are high GI foods, while chocolate cake has a lower GI value.
Also, foods that contain or are cooked with fat and protein slow down the absorption of carbohydrate, lowering their GI. For example, crisps have a lower GI than potatoes cooked without fat. However, crisps are high in fat and should be eaten in moderation.
If you only eat foods with a low GI, your diet may be unbalanced and high in fat.
Many studies have found that following a low GI diet may reduce blood sugar levels and improve blood sugar management in people with type 2 diabetes, also Following a low GI diet may help lower levels of both total and LDL (bad cholesterol), both of which are risk factors for heart disease.
Results of a 16-year study that tracked the diets of 120,000 men and women were published in 2015. Researchers found that diets with a high GL from eating refined grains, starches and sugars were associated with more weight gain.
Other studies show that a low GI diet may also promote weight loss and help maintain weight loss. However, data from another study indicated a substantial range in individual GI values for the same foods. This range of variability in GI values makes for an unreliable guide when determining food choices.
Reviews of trials measuring the impact of low-GI index diets on cholesterol have shown fairly consistent evidence that such diets may help lower total cholesterol, as well as low-density lipoproteins (the “bad” cholesterol) — especially when a low-GI diet is combined with an increase in dietary fiber. Low- to moderate-GI foods such as fruits, vegetables and whole grains are generally good sources of fiber.
list of foods Glycemic index
| FOOD | Glycemic index (glucose = 100) |
| HIGH-CARBOHYDRATE FOODS | |
| White wheat bread* | 75 |
| Whole wheat/whole meal bread | 74 |
| Specialty grain bread | 53 |
| Unleavened wheat bread | 70 |
| Wheat roti | 62 |
| Chapatti | 52 |
| Corn tortilla | 46 |
| White rice, boiled* | 73 |
| Brown rice, boiled | 68 |
| Barley | 28 |
| Sweet corn | 52 |
| Spaghetti, white | 49 |
| Spaghetti, whole meal | 48 |
| Rice noodles† | 53 |
| Udon noodles | 55 |
| Couscous† | 65 |
| BREAKFAST CEREALS | |
| Cornflakes | 81 |
| Wheat flake biscuits | 69 |
| Porridge, rolled oats | 55 |
| Instant oat porridge | 79 |
| Rice porridge/congee | 78 |
| Millet porridge | 67 |
| Muesli | 57 |
| FRUIT AND FRUIT PRODUCTS | |
| Apple, raw† | 36 |
| Orange, raw† | 43 |
| Banana, raw† | 51 |
| Pineapple, raw | 59 |
| Mango, raw† | 51 |
| Watermelon, raw | 76 |
| Dates, raw | 42 |
| Peaches, canned† | 43 |
| Strawberry jam/jelly | 49 |
| Apple juice | 41 |
| Orange juice | 50 |
| VEGETABLES | |
| Potato, boiled | 78 |
| Potato, instant mash | 87 |
| Potato, french fries | 63 |
| Carrots, boiled | 39 |
| Sweet potato, boiled | 63 |
| Pumpkin, boiled | 64 |
| Plantain/green banana | 55 |
| Taro, boiled | 53 |
| Vegetable soup | 48 |
| DAIRY PRODUCTS AND ALTERNATIVES | |
| Milk, full fat | 39 |
| Milk, skim | 37 |
| Ice cream | 51 |
| Yogurt, fruit | 41 |
| Soy milk | 34 |
| Rice milk | 86 |
| LEGUMES | |
| Chickpeas | 28 |
| Kidney beans | 24 |
| Lentils | 32 |
| Soya beans | 16 |
| SNACK PRODUCTS | |
| Chocolate | 40 |
| Popcorn | 65 |
| Potato crisps | 56 |
| Soft drink/soda | 59 |
| Rice crackers/crisps | 87 |
| SUGARS | |
| Fructose | 15 |
| Sucrose | 65 |
| Glucose | 103 |
| Honey | 61 |
| source: harvard.edu | |