Macronutrients (I)

In the previous presentation we learned, among other things, that food -although it is very varied because it depends on different factors-, must precisely define some quantitative and qualitative aspects of the nutrients it contains, in order to contribute to the correct functioning of the organism and guarantee its proper growth and development.

In this presentation we will begin the study of the nutrients that the organism needs in large quantities, known as macronutrients. As we have already explained, only three nutrients belong to this group: carbohydrates, proteins and lipids or fats.

Relationship between the body's energy needs and macronutrients

Our organism needs a continuous supply of the energy necessary to breathe, grow, maintain temperature, repair tissues, among many other functions. This energy (expressed in calories) is provided by macronutrients, which are found to a greater or lesser extent in all foods depending on their composition. For example, one gram of a food rich in fat provides approximately twice as much energy as one gram of a food rich in protein or carbohydrates.

Below we show the approximate values of energy provided by foods depending on their composition:

• 1 g of fat provides 9 kilocalories

• 1 g of protein provides 4 kilocalories

• 1 g of carbohydrate provides 4 kilocalories.

Let's see an example: A tablespoon of olive oil of about 10 grams of oil, contributes approximately 100 kilocalories (kcal).

We should know that alcohol when consumed in moderation - less than 30 grams of ethanol in a day - also considerably increases energy levels. Its yield is as follows:

• 1 g of alcohol provides 7 kilocalories.

The energy demands of infants vary throughout the different stages of a child's development, and this implies the need to adapt the intake to these variations, since both energy deficits and excesses cause health disorders in children that can become irreversible and have repercussions in later stages of their lives.

In order to have an approximate idea of the energy requirements of children, we show the following example:

• The energy recommendations for a girl or boy between two and three years of age are between 1300 and 1500 kilocalories per day, always depending on the physical activity they perform.

• The energy and nutrient recommendations for each child stage will be specified later in this course.

Carbohydrates or carbohydrates

Carbohydrates are molecules composed of carbon, hydrogen and oxygen that store a large amount of energy; this is released when the molecule is oxidized in our organism. Carbohydrates should supply between 55 and 60% of the total energy demanded by the body; the rest should be provided by fats and proteins.

Functions of carbohydrates

• Carbohydrates are a source of energy for immediate use by the cells. When we consume carbohydrate-rich foods, our body breaks them down into glucose. Glucose (blood sugar) is the main source of energy for the cells, tissues and organs of the body. For example: glucose provides almost all the energy used by the brain on a daily basis.

• They are fundamental in the metabolism of the nervous centers, because as we have already said, glucose supplies almost all the energy needed by the brain.

• They fulfill structural functions. For example, two sugars: ribose and deoxyribose, are structural components of the nucleic acids that form part of DNA and RNA.

• The dietary fiber present in some carbohydrates is attributed important digestive functions, since it softens and increases the volume of stool, favoring regular bowel movements and reducing the risk of colon disorders.

Types of carbohydrates

Carbohydrates are classified according to their nutritional characteristics into simple carbohydrates and complex carbohydrates.

Simple carbohydrates

Simple carbohydrates are less healthy than complex carbohydrates for the following reasons:

• They possess a simpler molecular structure so our body converts them into glucose quickly, increasing blood sugar levels immediately, causing the pancreas to overwork. Excessive consumption of simple carbohydrates for prolonged periods of time increases the risk of type 2 Diabetes Mellitus.

• They are absorbed quickly, so the feeling of satiety lasts very little time after ingesting them; this makes us feel the need to eat frequently, increasing the risk of becoming overweight or obese.

• Foods rich in simple carbohydrates: Table sugar, honey, industrial soft drinks, juices and nectars containing added sugars, sweets, cookies, chocolates, ice cream, etcetera.

Complex carbohydrates

Complex carbohydrates are healthier than simple carbohydrates for the following reasons:

• They are carbohydrates that are converted into glucose slowly; facilitating the increase of sugars in the blood gradually, avoiding excessive work of the pancreas.

• They are absorbed slowly, so the feeling of satiety lasts longer after ingesting them; this makes us not feel the need to eat very often, reducing the risk of being overweight or obese.

• They intervene in the decrease of intestinal transit, increase the frequency of evacuation and avoid constipation.

Complex carbohydrates nutritionally can be divided into two large groups:

• Starches: These are complex carbohydrates that are composed of many simple sugars joined together, which the body needs to break down to convert them into glucose. Foods rich in starches are bread, pasta, potatoes, corn, peas, etcetera.

• Dietary fiber: It is a complex group of substances that are part of plant foods that cannot be digested and absorbed by the small intestine, which undergo complete or partial fermentation in the large intestine, promoting beneficial physiological effects and helping to prevent chronic degenerative diseases. Foods rich in dietary fiber are: whole cereal flours, beans, spinach, artichokes, apples, carrots, potatoes, tomatoes, etcetera.