If the proteins have long been known nutritionists, research allows gradually to better identify their roles in the body and refine the recommended intake. Zoom on the latest advances.
Not to be confused with the meat or fish that contain the proteins are among the energy nutrients as well as carbohydrates (sugars) and fats.
What is a protein?
Every protein consists of the assembly of smaller molecules, amino acids. With digestion, protein ingested with food are broken down into amino acids. Once assimilated, they allow the body to renew body protein. Twenty amino acids can thus be combined, of which 9 are essential. The body can not produce them, they are required to be supplied by the diet.
What are the proteins in the body?
Protein is abundant in the human body: they represent 10 to 12 kilos of the body of an adult male, 250 to 300 g are renewed each day. About 40% of body proteins are localized in the muscles, but they enter the structure of all cells. The bones are thus constituted by a matrix protein (mainly collagen) on which is fixed calcium. Some body proteins have important functions: hemoglobin that can transport oxygen to various organs, insulin and glucagon are the hormones regulating blood glucose (blood sugar), the immunoglobulins or antibodies involved in the defense against infectious agents, digestive enzymes that convert food into digestible nutrients .
Do the children need a lot of protein?
Constituting each tissue, proteins are important nutrients for growing organisms. However, the recommended intakes are not much higher in children and adolescents compared to adults: 0.78 to 0.90 grams per kilogram of body weight per day, instead of 0.83 g (for example, a child weighing 10 kilos needs 8 9 g of protein per day). There are a few years, studies have left thinking that excess protein in childhood obesity favored a few years later. Although this link is now being questioned by researchers, it is not worth giving too much protein for young children, who spontaneously consume more than necessary.
In practice, in infants, breast milk or milk “first age” provides exactly the right amount of protein. Later, the contributions are met by 3 to 4 dairy recommended per day and a small portion of meat or fish of 10 g per year of age: 30 g to 3 years, 60 g to 6 years … From Similarly, pregnant women do not need more than 1 g of protein per kilogram of weight.
He must seniors insist on their protein intake?
From age 60, the recommended intake increases of 0.83 g of protein per kilogram of body weight per day to 1 g and 1.2 g even in people over 75 years. The goal is to slow the physiological muscle loss (sarcopenia), which slowly begins to quarantine but is increasing significantly after 65 years. Between 50 and 80 years, the loss of muscle is about 30% among people who do not practice regular physical activity … with consequences in everyday life: loss of strength and mobility little by little reduced, fall risk in the elderly. Recent studies show that it is possible to slow down this process and even maximize the muscle mass by practicing 1-2 times per week of strength training (strength against a load or force) and having sufficient consumption proteins. Among seniors, take most of the day protein in the same meal would facilitate the protein synthesis of organisme.
Sports they consume too much protein?
To retain more muscle mass than sedentary individuals, athletes (those who practice at least 1 to 2 hours per day, 4-5 times a week) need a little more protein: 1.2 g 1.5 g per kilo of body weight per day. Some, especially those who train in strength, tend to consume more, easily double. According to recent studies, these high intakes are not required, training outweighing protein intake to build muscle mass.
We know however that consumption of protein (about 20 g) associated with sugars (40 to 60 g) in the half-hour after workouts promotes muscle mass gain: for example, one large bowl of chocolate milk or 40 cl drinking yoghurt sucré4. The health consequences of excess protein are still imperfectly known, but it is shown to be harmful in people with kidney failure (sometimes unknowingly) 1.
They are the proteins to lose weight?
high protein sachets or Dukan diet, proteins are often being honored in dieting. It is shown to have a satiating effect, that is to say, they minimize hunger pangs from one meal to another and thus they help moderate energy intake. But if high protein diets do lose weight quickly, it is mainly because they provide very few calories. Nutritionists insist that a good intake of protein prevents muscle wasting. What is true, but on condition of not drastically reduce energy intake and practice enough physical activity (at least 30 minutes per day) .
What foods are proteins?
conventionally distinguished animal proteins, present in meat, fish, eggs, dairy and vegetable proteins in significant proportion in oil seeds (almonds, sesame …), legumes (soybeans and pulses ) and cereals.
The former are a bit better assimilated and / or better with essential amino acids. Eat balanced by pins of the National Health and Nutrition Programme (3 dairy and 1-2 servings of meat or fish per day, bread or starchy food at each meal) largely can meet the recommended intake of protein.
Should we rely on plant proteins?
The “semi-vegetarianism,” which involves eating vegetarian part-time, is a growing trend. Eat meat less often is beneficial to the planet, livestock is a major consumer of water and great purveyor of greenhouse gases. From a nutritional point of view, make a greater emphasis on plant proteins allows to consume less saturated fat (including excess promotes increased blood levels of bad cholesterol, or LDL) that are associated with animal protein in meats, cold cuts and cheeses. We can, for example, once a week, replace meat or fish by pulses, whose protein quality will be optimized by the association in cereals (each type of protein compensating for the weaknesses of the other point view of the essential amino acids): rice and lentils, chick peas and semolina (couscous), pasta and white beans (minestrone). Tofu “soy cheese” or plants steaks can also replace the time meat to time, provided they do not consume more than two soy products (juice, “yoghurt”, tofu, tempeh …) day , because of their intake of phytoestrogens, compounds similar to féminins6 estrogen.
Finally, for those who might be tempted to replace dairy products with vegetable juice, be aware that only the soya juice has a similar protein content of cow’s milk (rice juice, hemp, almond … are very poor ) and that these products do not provide calcium unless fortified.