Starch and sugars: still carbohydrates, but …


Carbohydrates in food can be very large molecules (complex carbohydrates) or small ones (simple carbohydrates or sugars). The most important kind of complex carbohydrate is starch that is found mainly in cereals and therefore in all foods that are made with them, such as bread, pasta, baked goods. Potatoes and legumes are also great sources of starch.

Sugars are the carbohydrates that give foods a sweet taste, and are mainly sucrose, like table sugar, or lactose and fructose, the sugars found in milk and fruit respectively.

The big difference between simple and complex carbohydrates is the time we spend digesting and absorbing them. Starch is a very large molecule made up of thousands of units of glucose, so it will take quite a long time to be completely broken down and to allow glucose absorption to occur. On the other hand, sucrose is formed only by one unit of glucose and one of fructose, so it will be broken down and its components absorbed more quickly. The result is that when we eat food that contains starch, our blood sugar, which is the concentration of glucose in the blood, increases slowly, whereas if we eat sweet foods, which contain sucrose, it will rise more quickly. If our diet always contains too many sweet foods, our blood sugar level will always rise rapidly, and this will cause the production of large amounts of insulin, the hormone used to regulate blood glucose concentration. In time, this can increase the risk of diabetes and obesity.

This is not only true for adults, but also for children and adolescents, whose diet often contains too many sugars, sometimes due to excessive consumption of carbonated drinks.
Although carbohydrates must be the main source of energy in a correct diet, they must be of the starch variety. Sugars should provide no more than 12% of an adult’s daily calories, and no more than 15% for a child. In practice, considering that the recommended daily consumption of energy for a 6-year-old child is 1640 kcal, the maximum amount of sugar consumed should be 246 kcal, which corresponds to 61 g of sugars. Remember that a teaspoon of table sugar is equal to 5 g, and that one portion (150 g) of apple with the peel contains 10 g of sugars. There are 50 g of sugar in 100 g of milk chocolate and 34 g in a portion of 100 g of sponge cake.

So, be careful. Don’t eat too many sweet foods, and especially don’t eat them after meals. The best time to eat sweet food is in the morning at breakfast, when we are finishing our nightly fast and we need energy, and quick.

Alessandra Bordoni
Department of Agricultural and Food Sciences
University of Bologna

*Italian Society of Human Nutrition (SINU): LARN – Reference Intake Levels for Nutrients and Energy for the Italian population – 4th edition. SICS ed.