Glycemic Index

Carbohydrates are very important for us – from them comes the energy needed by our muscles to function properly. It is particularly important for runners and other athletes – but how do we know when to eat? Some products give quick but a short boost of energy while others release it slowly and steadily, giving a feeling of satiety for a long time. The glycemic index was invented to help us understand this phenomenon and to make good eating choices.

GLYCEMIC INDEX

The glycemic index (ang. Glycemic index) determines how the product affects the level of glucose in our blood. It is defined as the percentage increase in blood glucose after eating a product portion containing 50 grams of digestible carbohydrates. For example – the glycemic index of 85 means that after consumption of 50 grams of the product, blood glucose levels will increase by 85% (such as after ingestion of 50 grams of pure glucose it would increase by 100% – glucose is a comparative food with GI = 100). It is calculated according to the formula:

GI of glucose = 100
GI<35 = low GI products (planning your diet, choose them the most often)
GI 35–64 = medium GI products (you can eat them occasionally)
GI >65 = high GI products (limit in the diet)

The glycemic index applies to carbohydrates only, because only they affect blood glucose levels. The higher the GI value of the product, the more violently higher rises blood sugar level after consumption, but it also falls more violently, causing the feeling of hunger. On the other hand, the low GI products cause more stable but lower blood sugar increase and its gentle descent, which allows to postpone hunger, being most effective in weight reduction.

When planning a diet based on low glycemic index, choose foods rich in fiber such as legumes, vegetables and fruit, whole meal grain products, lean meat and dairy products and healthy fats. Products consumed in their natural form have a lower glycemic index than processed foods (eg. cooking increases IG).

GLYCEMIC LOAD

The glycemic index is, however, only a part of the story. This indicator does not tell us how much will the blood sugar rise after eating a real meal, which is influenced by many other factors such as the amount of carbohydrates in individual servings. To understand the real impact of food on our body, we must take into account how quickly the product will raise blood sugar levels, but also how much of this sugar really gets there. For this, there is a separate indicator, called the Glycemic Load. It gives us a more accurate picture of the real effects of food on blood sugar levels. It is calculated according to the formula:

C – ammount of carbohydrates in a serving (in grams)
GI – glycemic index
GL – glycemic load

Glycemic load lower than 10 is considered low, an average is 10-20 LG, while more than 20 is considered high GL.

EXAMPLE:

Watermelon, having a high glycemic index (72), contains very few carbohydrates (5g) in a portion (100g), so it’s glycemic load is equal to 3,6
Rice noodles, with IG = 40, contain 22g of carbohydrates in a 100g portion, which gives us the GL = 8,8 – more than twice the watermelon, despite the lower GI.

REMEMBER

fiber slows the digestion of carbohydrates, resulting in slower burst of insulin into the blood
The less processed the food, the lower its glycemic index (eg. pasta cooked al dente has a lower GI than overcooked)
use sweeteners with a lower GI instead of sugar
eat slower! – The faster you eat, the faster the release of glucose into the blood
less ripe fruits have a lower glycemic index (starch didn’t yet manage to turn into sugar)
Other nutrients may slow down the action of digestive enzymes or gastric emptying (eg. a protein, fat, pectin, fiber, etc.).