Carbohydrates, Diet Energy

Carbohydrates are a group of nutrients that, together with fats and proteins, form what we call macronutrients, that is, the majority nutrients in food that, in addition to providing us with energy, cover different functions in our body. They are essential in our diet, so they must provide us with between 50 and 60% of the total energy in the diet. It is precisely foods rich in carbohydrates that form the base of the balanced diet pyramid.

Types of carbohydrates

Chemically they are organic compounds formed by hydrogen, carbon and oxygen, hence their name. We can also call them carbohydrates, a name that comes from the Greek and was attributed to them due to the sweet character of many of them. We classify them according to their chemical structure, differentiating between:

Simple carbohydrates

We also call them sugars because they generally give us a sweet flavor. They are a source of fast energy because their digestion is easy and they pass into the bloodstream providing fuel for the cells. Its consumption will be especially interesting after doing intense physical activity, or even during it.

They are the smallest carbohydrates; They are no longer subdivided into other units when digested, but are quickly absorbed due to their small structure. Among them we find glucose, galactose and fructose and others less known as D-ribose and L-arabinose. In general, all cells in the body can use glucose as a source of energy. Furthermore, under normal conditions glucose is the only energy substrate in brain cells. We find these nutrients in fruits and vegetables, honey, etc.

They are formed by the union of two or more monosaccharides, up to 10 units. The best known are: sucrose (glucose + fructose), lactose (glucose + galactose) and maltose (it is made up of two glucose molecules). In the digestion of these products, the enzymes of our body are in charge of separating these unions to obtain the corresponding monosaccharides. In the event of a deficiency of any of these enzymes, a food intolerance will be experienced, this is the case of lactose intolerance that occurs when there is not enough lactase, an enzyme that separates glucose and galactose that form lactose. We can obtain oligosaccharides from cane sugar, beets, vegetables, fruits, some legumes and cereals, and milk and dairy products.

Complex carbohydrates

They are large compounds that need a longer digestion time to be absorbed. This implies that the arrival of glucose into the blood when we ingest complex carbohydrates will be more gradual. A positive feature unless we need energy quickly after intense exercise or have to overcome a drop in blood glucose (hypoglycemia). The fact that the arrival of glucose to the blood is slower is going to be especially interesting for people with or reactive hyperglycemia.

We must also bear in mind that the passage of glucose into the blood does not depend only on carbohydrates but that digestion and absorption will be slower if it is accompanied by fats and proteins. Also the presence of fiber slows down intestinal absorption.

They are composed of more than 10 monosaccharides, and can be made up of thousands of them. The main ones are starch, glycogen and cellulose. Starch, also known as starch, is the way vegetables store carbohydrates. The starch forms small insoluble granules in cold water, so for its digestibility it must be cooked. Glycogen is the carbohydrate reserve of the animal world, in fact humans have glycogen reserves in the liver and muscle. Cellulose, for its part, is part of what we call fiber. We have polysaccharides in cereals and their derivatives, bakery products, pasta, semolina and flour…, in seeds, legumes, roots and tubers, such as potatoes or sweet potatoes. They are also carbohydrates ...

• Polyols: they are a group of carbohydrates with special characteristics because their absorption at the intestinal level is partial so that they provide us with a lower caloric content. For this reason they are used as sweeteners.
• Fiber: all those polysaccharides and oligosaccharides that are not digested in the small intestine and that are finally fully or partially fermented in the large intestine are considered. Specifically, cellulose is a support fabric for the plant world. Other fibers are the pectins that we find in many fruits, the inulin that is in some tubers, etc.

What are they for?

• They provide us with energy, between 50 and 60% of the energy we receive with food must come from carbohydrates. Let us remember that we need this energy for cell function, brain, muscle, etc.
• They serve as an energy reserve, in addition to circulating glucose levels in the blood that are maintained even when fasting, we will store carbohydrates or carbohydrates in the muscles and in the liver, in the form of glycogen.
• Some of them are part of the fundamental tissues of the body. They form, for example, nucleic acids, cartilage, mucus, etc.
• They avoid the use of proteins as an energy substrate, since proteins have other purposes in the body, such as forming tissues. The consumption of proteins for energy will only occur if a diet is insufficient in carbohydrates and this will lead to a situation of ketosis, with consequences such as alitosis, dehydration, headache ...

Where are they found?

We obtain these nutrients mainly through foods of plant origin. The exception is milk and, of course, dairy products, since milk provides us between 35 and 40 g of lactose per liter. Within plant foods, with the exception of oils, the rest provide us with more or less significant amounts of carbohydrates:

• Sucrose: in vegetables and fruits. It is a very abundant component in beets and sugar cane.
• Fructose: in fruit and its derivatives (compotes, juices, etc.) and honey.
• Lactose: in milk and dairy products such as yogurts and cheeses.
• Starch: in cereals and their derivatives (bakery products, pasta, semolina and flour ... legumes and tubers such as potatoes.

Carbohydrates and slimming diets

Due to multitude of foods rich in carbohydrates they have been associated with weight gain. Hence, many weight loss diets dispense with them or minimize them. You should not fall into this error because carbohydrates are necessary and should be an important part of our diet.

Otherwise, a carbohydrate deficiency can generate undesirable situations in the body such as ketosis, a metabolic situation whereby products called ketone bodies are produced in our body that must be eliminated from the body. They are expelled mainly through urine. Other effects can be dehydration, alitosis and headache and / or dizziness due to carbohydrate deficiency.

One to lose weight should provide us with fewer calories than we eat but should not exclude any food group.

Thus, carbohydrates provide us with energy, which does not mean that they are fattening. In fact, all foods provide us with energy and can contribute to us gaining weight if they are taken in excess, that is, if we ingest more energy than we expend through metabolism and physical activity that we carry out.

On the other hand, it is necessary to clarify that foods rich in fat or even alcoholic beverages can be considered to be more fattening since while carbohydrates provide us with 4 Kcal per gram, alcohol provides us with 7 Kcal / g and fats 9 Kcal / g . Among them, except for alcohol, which is toxic and should be avoided, both fats and carbohydrates are absolutely necessary nutrients to cover different functions in our body.

• They are important because they give us the energy we need to function.
• They provide at least half of the total daily calories.
• If we diet we must also include them in our menu.

Mercè Gonzalo Diploma in Human Nutrition and Dietetics