Starch is a complex sugar that serves as a carbohydrate reserve for plants. It is essential in nutrition because it is the main source of energy that we can provide to the body. However, like starchy foods which contain significant quantities, starch is sometimes demonized because it is accused of causing weight gain. What is it really? In what foods are they found? Is it digestible? The answers from Raphaël Gruman, dietitian and nutritionist in Paris.
Definition: what is starch?
Starch is a complex sugar, composed of two homopolymers (amylose and amylopectin), themselves made up of several units of D-glucose (simple sugar) linked to each other. Starch is to plants what glycogen is to living beings, namely their main energy reserve.
Its name comes from the Latin amylun, which means “unground”. “Indeed, to be assimilated by the body, starch must first be cut into monosaccharides by digestive enzymes called amylases. explains Raphaël Gruman. It is for this reason that starch is considered a “slow sugar”, because its digestion and assimilation by the body requires more work and time than for so-called fast simple sugars.
Role of starch: What are its health benefits?
Complex carbohydrates, and therefore starch, are essential to health because they provide the body with slowly assimilable energy. “Half of the energy we consume should ideally come from carbohydrates, and of these the vast majority should be complex carbohydrates. reminds the dietitian. Indeed, as explained previously, starch is a long chain of glucose molecules, which needs to be broken up in order to be assimilated by the body.
Thus, unlike simple sugars which pass directly into the blood after ingestion and can be immediately used by the body, starch is gradually released into the blood, and allows prolonged and lasting use of energy. . “This is what makes starchy foods filling and interesting to avoid cravings and cravings between two meals. summarizes the nutritionist. When they are correctly integrated into the diet, they are therefore valuable aids in maintaining a stable weight, because they help limit snacking while avoiding hypoglycemia. Foods rich in starch are also of great interest for children – active and growing – and for athletes, who need slowly released energy.
What about the glycemic index of foods rich in starch?
But if starch is naturally considered a slow sugar, i.e. one of gradual assimilation, this is not always the case. The glycemic index (GI) of a food thus makes it possible to assess the capacity of a sugar to be absorbed more or less quickly and therefore to raise blood glucose (blood sugar level) more or less quickly. There are several variables that influence the glycemic index of a food:
- Cooking the food: the longer a food is cooked, the higher its glycemic index rises, because cooking tends to break up large starch molecules;
- Processing a food: grilled foods (rusks, crackers, etc.), puffed foods (children’s cereals, popcorn, rice cakes, etc.) undergo high temperature cooking which breaks the starch molecules into small sugar molecules that are more quickly assimilated;
- The fiber and protein content of the food: fiber slows the absorption of carbohydrates, as does protein. Thus, legumes (chickpeas, lentils, red beans, etc.), which are both rich in fiber and protein, have a lower GI than pasta or white rice.
Where is starch found?
Starch therefore constitutes the energy reserve of plants, which is used to ensure its growth. It is found mainly in cereals (wheat, rice, corn, spelled, oats, etc.), in roots and tubers (potatoes, sweet potatoes, cassava, Jerusalem artichokes, crosnes, etc.), in certain seeds (chestnuts) or even in the banana. “The banana is one of the rare fruits that contains starch. It is mainly found in green, therefore unripe, bananas. The more the banana ripens, the more complex carbohydrates become simple carbohydrates. says Raphaël Gruman. The proportion of starch contained in plants varies greatly, and ranges from 20% for potatoes to 55% in wheat (dry) and 65% in corn (dry).
Is there gluten in starch?
Gluten is the protein fraction contained in certain cereals (wheat, rye, oats and barley), while starch is a carbohydrate: they are therefore two distinct and different nutrients. “On the other hand, there is gluten in a certain number of foods rich in starch: pasta, semolina, bread and all foods that contain wheat (biscuits, pastries, pizza, etc.).” says Raphaël Gruman. People with gluten intolerance should therefore favor foods that are sources of starch and do not contain gluten: rice, corn, legumes, quinoa, potatoes, sweet potatoes, etc.
Can starch be bad for your health?
Starch as such is not bad for your health, but as is the case with all foods, those rich in it need to be consumed in moderation, especially when watching your weight and that caloric needs are moderate. “Between teleworking which is becoming more widespread and means of transport which are increasing, we live in an increasingly sedentary society. However, the less we move, the less calories we burn and the lower the need for complex carbohydrates. reminds the dietician. A 40-year-old woman who is sedentary and slightly overweight will therefore have every interest in limiting her consumption of starchy foods so as not to risk gaining weight.
Is starch digested well?
In most cases, starch is digested very well after cooking. Its digestion begins in the mouth with salivary amylase. It continues in the duodenum and in the small intestine thanks to pancreatic and intestinal amylase. The action of these amylases leads to the appearance of a simpler sugar, maltose, itself transformed into glucose as digestion progresses.
But certain starches, called “resistant starches” are not completely broken down during digestion, and are found in the digestive tract where they behave like soluble fibers. These foods are rather beneficial for health because they maintain the intestinal flora and have a prebiotic role. These resistant starches are found in certain particularly high fiber foods such as legumes and whole grains.
What are the chemical properties of starch?
Starch has interesting chemical properties that are sought after in cooking. Indeed, if it is insoluble in cold water (which explains why it is not digestible when raw), it forms when cooked – from 60°C – a thick gel called starch. starch. It is amylose and amylopectin which constitute starch, which unfold and intermingle during cooking, capturing several times their weight in water. Well-cooked starch therefore has binding and thickening properties, useful for preparing creams or sauces such as béchamel, white sauce or crème pâtissière.
What are the industrial uses of starch?
Starch is widely used in the chemical industry, for the manufacture of paper and cardboard, but also in cosmetics, medicines and detergents. In the food industry, it is used in the form of modified starch (E1440) for its thickening, binding, texturizing, thickening or gelling properties. It is an additive without danger to health, which appears in Annex I of the additives authorized without restriction in European Directive 95/2/EC.