Glucids (sugars) – are nutrients in the composition of which enter C, H, O2. After the complexity of their molecule, they splits into the following categories:
- monosaccharides: glucose, fructose, galactose;
- disaccharides: sucrose, maltose, lactose;
- poliols: isomalt, sorbitol, maltitol – are so-called sugar alcohols;
- oligosaccharides: maltodextrins, fructo–oligo–saccharides – are made up of 3-9 carbohydrate units;
- polysaccharides: starch, glycogen, cellulose, pectins, hydrocolloids – have over 10 sugar units, reaching up to thousands of units.
The role of carbohydrates in the body:
– glucids primarily have an energetic role – each gram releases 4.1 calories by burning.
– the antitoxic function of the liver is linked to glycogen stores – it can be said that carbohydrates have an important role in detoxifying the body after effort;
– if during contraction, the muscle can also use the energy from proteins and carbohydrates, the central nervous system and the myocardium are sensitive to the lack of carbohydrates;
– glucids have also a plastic role, they can form some amino acids that enter the constitution of cellular proteins, helping to increase and restore tissues;
– glucids also take part in the thermoregulation of the body;
– glucids have a catalytic role in lipid metabolism.
The glycemic index:
The glycemic index – is a system that classifies foods rich in carbohydrates depending on their ability to affect their blood sugar levels. Thus, foods and beverages containing fast-acting carbohydrates after ingestion have a high glycemic index. The fastest is pure glucose, so its glycemic index is considered to be 100.
Some athletes are very sensitive to lowering blood glucose produced after 30 minutes or even hours of food intake, causing sweating, trembling, dizziness. For these athletes, it is important to determine the optimal interval from diet to competition, but also the type of glucide indicated for administration, according to the glycemic index.
For the usual consumption, foods with a glycemic index of 75 are recommended !
Before long efforts, foods with low glycemic index are recommended. After the effort, foods with a high glycemic index favor filling the glycogen deposits faster.
Particular attention to the association of foods with other compounds (lipids, fibers, proteins) as it can alter the glycemic index !
Carbohydrate reserves in the body:
In the human body, CHO is stored in the form of long chains, consisting of glucose units (glycogen). Glycogen is found in muscle and liver and is comparable to starch from potatoes, bananas, other vegetables.
The amount of glycogen in the liver varies regularly depending on the amount of glucose delivered to the liver by the food intake and the amount of glycogen decomposed to provide the blood glucose needed for the various activities.
Liver glycogen stores increase after meals and decrease between meals, especially at night because the liver permanently supplies blood glucose for the purpose of maintaining blood glucose constantly.
The amount of glycogen in muscles is about 300 g for sedentary people and over 500 g for people with high levels of workout by combining effort with a CHO-rich diet. This quantity can provide from 1200 – 2000 kcal.
The main source of energy in the body is catabolism of carbohydrates and the main way of metabolizing glucose is cellular oxidation. Depending on the quantitative energy needs, glucose is transformed by passing through several stages in the pyruvate.
“Glucose – lactic acid” transformation is reversible, which means that increased levels of lactic acid blood poisoning can be diminished by transforming lactate via gluconeogenesis back into glucose that can be deposited as glycogen. The lactate can also be oxidized or transformed into fat.
In addition to cellular oxidation that is the primary glucose metabolic pathway, glucose intermediate metabolism also includes other processes, namely:
- glycogenogenesis (glucose synthesis from glucose);
- glycogenolysis consists in the degradation of cellular glycogen by gradual detachment of glucose molecules under the action of specific enzymes;
- gluconeogenesis (synthesis of glucose from non-glucidic products of intermediate metabolism);
- lipogenesis (lipid synthesis from glucose).
The liver has a major role in the metabolism of carbohydrates!
Blood glucose level – reflects the dynamic balance between the amount of glucose released by the liver in the systemic circulation and the amount of tissue used. Maintaining this level within constant limits is the result of the involvement of nervous factors, the main role of which is held by the hypothalamus and pancreatic hormones, insulin and glucogen.
Insulin – is synthesized in the B cells of Langerhans’ islands and is rapidly attached to tissues, especially in the liver and kidney. It is the hypoglycemic hormone of the body having an activating effect on glycogenogenesis, lipogenesis, glucose penetration in cells, and increased tissue glucose consumption.
The type and amount of carbohydrates we need to take:
The carbohydrate ratio depends on several factors: age, sex, activity, environmental conditions, etc..
On average, at the athletes, the need for carbohydrates is about 4.5-10 g per kilogram body / 24 hours, which is 600 to 800 g. (55 – 60% of the caloric requirement of the body is covered with carbohydrates).
- The carbohydrate requirement for the sedentary population is 50%.
- The reason for the increase in carbohydrate requirement in athletes results from the fact that fatigue arising from physical exercise is associated with a decrease in glycogen stores.
- Most athletes have a glucose requirement of 4.5-6 g / kg body weight / day. In the case of 70% high carbohydrate intake, this is about 7 g / kg body weight / day, and in the case of very intense training at 9-10 g / kg body weight / day.
The base of the carbohydrate in the food ration is made up of vegetables, of which we mention: cereals (wheat, corn, corn flakes, oats, etc.), pasta, rice, dried fruits (plums, apricots, figs, raisins, etc.), dried vegetables (beans, soybean, lentils, peas, etc.), bread, potatoes, fruits and vegetables.
Other foods high in sugar are: sugar, honey, candy, syrup, jam, marmalade, Turkish delight. Carbohydrates are also found in the following foods: milk, liver, oysters, etc..
Cellulose – should be consumed by athletes in the amount of 50-100 g / day, in the form of vegetables, fruits, black bread, etc..
The use of a CHO supplement on food after digestion, absorption and take-up by blood portal leads to increased blood glucose in systemic circulation. This will reduce hepatic glycogenolysis in order to maintain high blood glucose and on the other hand ensure an increased intake of glucose in the muscles in activity.
For an effort of more than 45 minutes, a minimum of 20 g is recommended, an optimum of 80 g of CHO consumption per hour of effort. Preparations administered before or during exercise should have a low content of cellulosic fibers and a high glycemic index, as opposed to normal meals during training periods.
The primary sources in the effort are:
- monosaccharides (glucose);
- disaccharides (sucrose, maltose);
- polymers (malt, maltodextrins);
- soluble starch.
Pure Fructose – does not influence insulin secretion, but it is absorbed slower than glucose and inhibits less fatty acid mobilization, so there is an indication of 1 g / Kg body intake during exercise. The rate of fructose oxidation in order to provide energy is still lower than that of glucose probably due to a higher affinity of the glucose muscular hexokinase. Therefore, it is recommended to administer the combined glucose with fructose, sucrose, maltose and soluble starch to obtain an extra amount of energy.
For marathons, sugar beverages are useful during the race by preserving muscle glycogen and restricting the fatty acid mobilization of fat tissue with the predominant use of carbohydrates for energy. Advantages are due to the fact that oxidation of fatty acids requires more oxygen to produce the same amount of energy, so it is less efficient in terms of oxygen consumption.
Daily carbohydrate intake is 55-70% of the food ration. For athletes, on average, the need for carbohydrates is about 4.5 – 10 g per Kg body / 24 h (600 – 800 g).
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