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The glycemic index (IG) represents the capacity of carbohydrates contained in foods to raise blood sugar (a value that indicates the amount of glucose present in the blood). To quantify the glycemic index of a food it is necessary to take 50 grams and monitor the blood sugar levels in the following two hours. These values will then be compared with those of the reference standard which in this case is glucose or white bread (glycemic index = 100). If a food has a glycemic index of 60 it means that by ingesting 50 grams of that food the blood sugar rises by 60% compared to what happens with 50 grams of glucose.
In general, the more digestible a carbohydrate is, the greater its glycemic index will be.
- Not all carbohydrates are the same:
- some are absorbed quickly and cause a rapid rise in blood sugar (high GI)
- others release glucose more slowly (low GI).
This parameter is obtained by comparing the glycemic index of a certain food to its average portion. It is therefore sufficient to multiply the IG of a given carbohydrate (eg fructose IG = 20) for the quantity assumed (for example 30 grams). In the specific case the glycemic load of the meal is 20 x 30 = 600.
The quantity of what you eat is therefore more important than the glycemic index of the individual food, in order not to fatten and keep your blood sugar and appetite under control. Excluding from your diet some foods just because they have a high glycemic index does not make any sense, it is enough, simply, to have a balanced relationship with food avoiding excesses.
The following table shows the glycemic index of some foods belonging to different groups. For easier identification we have divided the food into three classes (high, medium and low glycemic index).
Glycemic Index Table
| HIGH GLYCEMIC INDEX | MODERATE GLYCEMIC INDEX | LOW GLYCEMIC INDEX | |||
| FOOD | IG | FOOD | IG | FOOD | IG |
| Maltose | 109 | Pineapple | 59 ± 8 | Plum | 39 ± 15 |
| Dates (dried) | 103 ± 21 | Ice cream | from 57 to 80 | Apricot | 38 ± 2 |
| Maltodextrin | 100 | Kellogg's Special K | from 54 to 84 | Pere | 38 ± 2 |
| Glucose | 100 | Muesli | from 39 to 75 | Fish sticks | 38 |
| White bread | from 30 to 110 | Coke | 58 ± 5 | Yogurt | 36 ± 4 |
| Cornflakes (Kellog's) | 91 | Barilla Spaghetti cooked 10 minutes | 57 | Boiled peas | 32.9 |
| Honey | from 32 to 95 | Banana | 52 ± 4 | Lean milk | 32 ± 5 |
| Baked potatoes | 89 ± 12 | Kiwi | 53 ± 6 | Soya milk | 32 ± 2 |
| Cheese Pizza (Italy) | 80 | Mango | 51 ± 5 | Canned peaches | from 30 to 71 |
| Gatorade | 78 ± 13 | Rye bread | from 50 to 64 | Boiled beans | 29 ± 9 |
| Frum bread. gluten free | 76 ± 5 | Pineapple juice | 50 ± 4 | Fresh peach | from 28 to 56 |
| French fries | 75 | Grapefruit juice | 48 | Apple | from 28 to 44 |
| Pumpkin | 75 ± 9 | Macaroni | 47 ± 2 | Sausage | 28 |
| Crackers | from 52 to 98 | Carrot | 47 ± 16 | Whole milk | 27 ± 4 |
Melon | 75 | Grapes | from 46 to 59 | cherries | 22 |
| Watermelon | 72 ± 13 | Pears in Box | 46.0 | Lentils | from 22 to 34 |
| Popcorn | 72 ± 17 | Low-fat fruit yogurt | 45 | Pure fructose | 19 ± 2 |
| Arborio rice | 69 ± 7 | Orange | 42 ± 3 | Boiled soy beans | 18 ± 3 |
| Fanta | 68 ± 6 | All-Bran | 42 ± 5 | Light yogurt | from 14 to 45 |
| Sucrose and Cane Sugar | 68 ± 5 | Apple juice | 40 ± 1 | peanuts | 13 |
| Croissant | 67 | ||||
| Biscuits (Oro Saiwa, Italy) | 64 ± 3 | ||||
| Boiled common potatoes | from 56 to 101 | ||||
| Sweet potatoes | 61 ± 7 | ||||
**NOTE:
When we talk about the glycemic index of a food, it is important to define a range of values that takes into account all those parameters that can influence it positively or negatively. The glycemic index of a food varies, for example, with:
- its degree of ripeness (increases if the fruit is ripe)
- the variety (green apples "for diabetics" do not have the same IG as red ones)
- temperature and cooking time (increases with heat)
- the format of the pasta
- the quantities of ingredients used (especially in the case of industrial products)
For all these reasons it makes little sense to propose an average value that could mislead the consumer leading him to make incorrect food choices.
High glycemic index foods
Enemies of health
Consuming foods with a high glycemic index:
- the blood sugar rises more and more quickly;
- the insulin response is more pronounced;
- the body gets used to preferentially using sugars instead of fats; the transformation of sugar into fats also tends to increase (overweight);
- oxidative stress increases (premature aging, cancer risk);
- after 2-4 hours the blood sugar drops and hunger returns;
- over time there is an overload of work for the pancreas which initially causes insulin resistance and subsequently the appearance of diabetes;
- the risk of tooth decay is greater.
A diet that is too rich in foods with a high glycemic index (high overall glycemic load) increases the risk of cancer, especially in the gastrointestinal tract and the ovary. It is not yet clear whether this relationship is due to the excessive consumption of foods with high GI, the consequent overweight, or to a diet too rich in sugars and poor in fruit and vegetables.
For the athlete it is important to avoid taking too many high glycemic index foods before the competition or training. In fact, the consumption of simple sugars would rapidly increase the blood sugar level by stimulating a prompt secretion of insulin with consequent secondary hypoglycemia, a reduction in fat oxidation and possible rapid depletion of glycogen stores.
Carbohydrates with a high and moderate glycemic index are instead useful for promoting recovery in post-training.
Low glycemic index foods
Foods with a low glycemic index have a significant effect on cardiovascular risk as they attenuate postprandial hyperinsulinemia and promote an increase in good cholesterol (HDL).
It is interesting to note that the glycemic index of foods does not depend only on the type of carbohydrates it contains. Rice and potatoes, despite being rich in starch (polysaccharide) have a glycemic index higher than fructose and many sugary fruits. Dietary fiber in fact slows gastric transit time, with a reduction in the rate of absorption of the sugars taken along with the fiber. A similar argument can be made for fats (skimmed milk has a higher glycemic index than the whole one) and to a lesser extent for proteins.
Intake of low glycemic index foods before the competition has a positive effect on the performance of athletes.
