Carbohydrates: Functions and Role in the Diet

Carbohydrate functions

Carbohydrates are our main energy source especially during intense physical activity. They also have a plastic function and are involved in the formation of nucleic acids and nervous structures.

After being transformed into glucose, carbohydrates can go against three different metabolic processes:

they can be used by cells to produce energy

they can be stored in the liver and muscle reserves in the form of glycogen

they can be transformed into fat and deposited as such if the glycogen stores are saturated

There are amino acids, vitamins and essential fatty acids but there are no essential carbohydrates. However the role of carbohydrates in our body is fundamental. The central nervous system alone needs about 180 grams of glucose a day to perform its functions optimally. Some blood cells (red blood cells) and adrenal medullary cells also use glucose exclusively as a primary energy source.

If needed, our body can obtain glucose from the carbon skeleton of some amino acids and from the glycerol contained in fats. In conditions of extreme glucose deficiency (prolonged fasting) this process leads to the formation of toxic substances, the ketone bodies that lower the blood pH with serious consequences for the body.

Blood glucose regulation

Blood glucose represents the amount of glucose present in the blood (mg / dl). The human body has a series of mechanisms that keep it relatively constant throughout the day (about 70 mg / dl fasting) regardless of the amount of carbohydrates consumed in the diet.

The liver is the main organ involved in the regulation processes: when the blood sugar drops it releases the glucose contained in the hepatocytes, when it rises it stores it in the form of glycogen. This allows you to keep your muscle protein stocks intact.

Excess carbohydrates, the glycemic index

Generally the diet of industrialized countries is very rich in carbohydrates. In particular, in the last one a large use was made of simple carbohydrates, that is of mono and disaccharides which are added during the preparation to sweeten food.

Excessive consumption of sugar is related to diseases such as obesity, dental caries and diabetes. It is therefore advisable to limit the use of carbohydrates with a high glycemic index, preferring those with a low glycemic index.

The glycemic index ( IG ) represents the rate at which blood glucose increases following the intake of 50 grams of carbohydrates. The higher the glycemic index, the faster the absorption of carbohydrates.

Simple sugars (high GI) enter into circulation very quickly, making it necessary to over-produce insulin which in the long run can lead to a functional decline of the cells responsible for its production (diabetes). The abrupt drop in blood sugar that ensues in addition to tiring the subject, making him more tired and less concentrated, leads to a premature appearance of the hunger stimulus. This leads to a vicious circle that can easily lead to obesity.

Carbohydrates - Chemistry, Functions, Food Additives

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Carbohydrate deficiency, high protein diets

Given the negative consequences of a high carbohydrate diet, in the last decade many food models with very low carbohydrate content have been proposed. However, the extreme reduction of carbohydrates is not without side effects.

The excess of proteins and fats increases the danger of hypercholesterolemia, of liver and kidney diseases and of some cancers. Moreover, in the case of extreme lack of carbohydrates, ketone bodies form (as in the untreated diabetic) which acidify the blood and can lead to coma.

It is therefore necessary to find the right balance between the levels of intake of the various nutrients, without excluding any a priori.

How many carbohydrates?

We have seen the danger of both an excess and a carbohydrate defect.

The Mediterranean diet provides a glucose intake that varies between 55 and 65% of the daily calorie intake. At the same time, the consumption of simple sugars should not exceed 10-12% of the total daily energy.

However, in light of the latest research in the food field, we recommend sticking to the lower limit of this range, that is, to introduce a daily quantity of carbohydrates between 50 and 55% of the total energy and trying to limit the consumption of carbohydrates simple.

Green light therefore for the consumption of foods rich in fiber such as vegetables and non-sugary fruit. Yellow light for starchy foods like bread, pasta and rice; red light for refined sugars (honey, sugar, glucose and derivatives such as glucose syrup and maltose).

Carbohydrates and sports

During intense physical activity our body uses almost exclusively glucose to satisfy the increased energy demands. It is therefore very important that the sportsman's diet provides the right carbohydrate intake. However, a distinction must be made between endurance sports and power sports.

If in the former (cycling, walking, cross-country skiing, running, etc.) the recommended daily intake is 55-65% of the total energy (depending on the frequency and duration of training) in the seconds it is good to stay in the intervals recommended for the sedentary population (50-55%) increasing, if necessary, the protein intake.