If you are not diabetic, you might not pay much attention to your blood glucose levels, since the body normally maintains glucose balance regardless of the type of food or amount of physical activity. However, the situation is different for those with diabetes or at risk of developing it, where controlling blood sugar levels becomes a daily challenge.
Although blood sugar stability is influenced by multiple factors, such as stress, sleep deprivation, illness, dehydration, and even over-exercising or lack of movement, diet remains the most important factor in maintaining this balance.
Controlling carbohydrate intake is a fundamental pillar in healthy nutrition for diabetics, but not all carbohydrates are equal in terms of their impact on blood sugar. Hence, the glycemic index has emerged as a tool used to measure the speed and effect of carbohydrate-rich foods on raising glucose levels.
What is the glycemic index?
Kelly Gaines, a dietician at Houston Methodist Hospital, explains that the glycemic index is a scale that classifies foods from 0 to 100 based on the speed of their impact on blood sugar levels. A lower value represents a slower, more stable effect, while higher values indicate a rapid rise in blood sugar.
Gaines classifies foods into:
- Low glycemic index: from 0 to 55
- Medium glycemic index: from 56 to 69
- High glycemic index: from 70 to 100
Typically, low-glycemic foods are digested slowly and are often rich in fiber, protein, or healthy fats, while high-glycemic foods contain refined carbohydrates and rapidly absorbed sugars.
Since the glycemic index only measures the impact of carbohydrates, foods without them, like meats and fish, are not included in this classification.
Factors that raise or lower the glycemic index
Gaines points out that the way food is prepared plays a central role in determining its glycemic index. The more processed the food, the higher its impact on blood sugar. Cooking also facilitates digestion, which may increase the glycemic index, along with the ripeness of the food, as ripe fruit raises sugar levels faster than unripe ones.
A useful tool… but not perfect
Despite the popularity of the glycemic index, Gaines believes it is a limited tool that does not accurately reflect everyday dietary reality. Studies often rely on eating the food alone, whereas foods are usually consumed as part of meals that include proteins and fats which slow the absorption of sugar.
Moreover, the glycemic index does not take into account the serving size, as the values are calculated based on the consumption of 50 grams of carbohydrates, which is an unrealistic amount for some foods like fruits and vegetables.
For instance, 50 grams of carbohydrates equals two slices of white bread, but it also equals about three cups of blueberries, a quantity rarely consumed in one meal.
A more accurate alternative
As a more realistic alternative, Gaines suggests the glycemic load, which combines the glycemic index with the serving size. This measure is more accurate because it considers the actual context of food consumption.
The glycemic load is classified into:
- Low: 0 – 10
- Medium: 11 – 19
- High: 20 and above
For example, although cooked beets have a medium to high glycemic index, the glycemic load for one cup of them is low, making it a healthy choice when consumed in moderation.
What is actually the better alternative?
Instead of overly focusing on numbers, Gaines recommends paying attention to the degree of food processing, increasing the consumption of whole foods like natural vegetables and fruits, and limiting highly processed foods.
She also advises following the “healthy plate” rule consisting of:
- Half the plate of non-starchy vegetables
- One quarter of the plate with whole grains or legumes
- One quarter of the plate with low-fat protein
This approach is simpler and more effective in supporting body health and regulating blood sugar levels.
