Fructose is a member of the carbohydrate family, namely, simple carbohydrates or sugars. It can be found in our diets as it is, as fruit sugar, or as another molecule with a sweet taste: sucrose. This, also called “table sugar”, is made up of glucose and fructose. The sweet taste we experience eating foods that contain sucrose is linked to the presence of fructose, which is able to stimulate the receptors for taste in our mouth.

Glucose and fructose have the same energetic strength (4 kcal / g), but fructose is considered a “low-calorie” sweetener. Why is this? The reason is simple: fructose has a greater sweetening power than sucrose, therefore to have the same amount of sweetness, a smaller amount of fructose is needed compared to sucrose, and this will lead to a lower consumption of energy. But watch out. The way we metabolize fructose is different from that of the other component of sucrose, glucose. When absorbed, glucose, which is also found in starch, causes an increase in blood sugar (glucose concentration in the blood), which is immediately regulated by the production of the insulin hormone. The body’s cells respond to the insulin, and this metabolic response allows the blood sugar to return to normal.

Diabetics, and numbers of overweight people too, are not very “sensitive” to insulin and therefore struggle to keep their blood sugar within the normal range. The absorption of fructose raises the blood sugar less than sucrose, and its metabolism does not depend on insulin. For this reason, foods containing fructose instead of sucrose have been developed for diabetics. In non-diabetic people this substitution does not make a lot of difference, and even the calorie difference is small. Moreover, many studies have shown that too high a fructose intake can lead to obesity, giving the opposite effect. Obviously this happens due to a high intake of fructose, not for those that consume the recommended amount of fruit and general simple sugars. On the other hand, some attention should be paid to foods produced containing fructose or fructose syrup, both industrially and at home, which could lead to too high an intake of this carbohydrate. And of course, we must not eat too many sweet foods, keeping in mind that carbonated drinks are often a high source of simple sugars, which should not exceed 15% of the total energy consumed. This means that, in a 2000 kcal diet, we should not consume more than 75 g of sugar each day. To find out how much sugar is in a product, just look at the label, remembering that figures are often given for every 100 g or 100 ml, and therefore you have to alter this to apply to what you actually consumed.

Alessandra Bordoni
Department of Agricultural and Food Sciences
University of Bologna