For more than two decades, a debate has erupted over carbohydrates and the glycemic index. It seems that diet experts and nutritionists can not agree. Some argue that the glycemic index is a valid tool to assess the effect of food on health and body composition. Others disagree, insisting that other factors should be considered.
As a result of the commotion, as well as the popularity of certain diets, foods with a high glycemic index are often vilified, while those with a low glycemic index are ratified as good. However, the truth is that much of the controversy is the result of a misapplication of research that, in fact, has limited relevance in the real world.
Foods with a high glycemic index are often vilified, while those with a low glycemic index are ratified as good. However, the truth is that much of the controversy is the result of a misapplication of the investigation.
What is the glycemic index?
To begin with, it is important to understand what the glycemic index actually is. The glycemic index of a food (GI, for its acronym in English) is a measure of its ability to increase blood sugar. This is determined by the consumption of a standard amount of carbohydrates, generally 50 g, in a food test. The test meal is consumed after an overnight fast and the blood glucose levels are measured two hours later. The response to glucose in the test meal is compared to the glucose in the diet, which has a glycemic index of 100. Foods with a GI of 55 or less are considered low GI foods. Foods ranging from 56 to 69 are moderate and those with a GI of 70 or more are considered high.
Why is the glycemic index controversial?
The GI is controversial mainly because the results of the test on which many people base their opinions are problematic.
In tests, the GI of a food is determined by its consumption in a fasting state. This puts the relevance of the test results automatically in doubt, since the situation is outside a realistic context. In reality, a person spends most of the day in a postprandial state, that is, a state of food and not in a state of fasting. Complete digestion and absorption of a food can take four to eight hours, or longer, depending on the size of the food. The superposition of absorption from one meal to another can influence the GI of individual foods.
Another problem with the studies is that the source of carbohydrates consumed during the GI test is in isolation.However, in daily life foods are usually a combination of macronutrients, and not a single and isolated macronutrient. And factors such as the fiber, protein and fat content of a food can affect the GI of any other food that is consumed.
To top it off, the GI is an average response to a given food. This varies widely with food subtypes and is even affected by the way a food is cooked.
What does the research say about the glycemic index and health?
Regarding health blood markers, diets with low GI are generally superior to high GI diets.
But once again, the limitations of the investigation must be considered. In many cases, the total amounts of carbohydrates, proteins, fats and fiber do not correspond, so it is impossible to determine whether the positive health effects were solely due to the low GI value of the food or other factors., as the protein, fiber or fat levels of the food.
When studies attempt to match macronutrient contents between comparison diets, high GI groups are usually artificially fed with a high proportion of sweets and desserts processed to meet the condition. In contrast, low GI diets usually contain more whole and minimally processed foods.
So, again, it's not necessarily a high GI food that makes it a bad choice. There are healthy whole foods with a high GI and, on the contrary, there are junk foods with a low GI, belying the well-known rule that less is better.
James Krieger, nutritionist (author and researcher) and founder of Weightology, a weight-control information website, agrees that it is not the GI alone that determines the merit of a food.
"Some less healthy, energy dense and high-calorie foods are actually low GI, like a Snicker's bar," he explains. "Similarly, some healthier and lower calorie choices have a high GI, such as baked potatoes".
Glycemic index and weight control
Focusing on the important
One of the main problems of judging GI-based foods is that you unnecessarily eliminate healthy foods from your diet. For example, it is not uncommon for people concerned about GI to eliminate carrots from their diet. A better approach, however, is to try to get your carbohydrate portion from whole and unprocessed carbohydrate sources such as fresh fruits, vegetables, potatoes, sweet potatoes, peas, beans and squash. This ensures that most of your options are rich in nutrients, instead of high in calories.
The next step is to place processed grain products, such as bread, pasta, rice and cereals, second in the hierarchy.Consume them with discretion, since those who are not very physically active may not have the caloric budget to eat these foods in addition to whole foods.
Refined desserts, sweets and added sugars, on the other hand, should be consumed sparingly throughout the week.
Being fussy about the GI of individual foods is another potential pathway for pathological perfectionism in food and false food discrimination. Ultimately, worrying about GI is an unnecessary burden that does not necessarily lead to better health.