The human organism is an unstable and open system , so it needs a constant supply of energy and exchange of materials with the external environment in order to survive. This biological reality is carried out, basically, through respiration, excretion and food-nutrition.

The feed is obtained from the environment a series of products, natural or processed, called foods and containing a number of chemicals called nutrients , and other substances themselves each configuring its sensory qualities (texture, aroma, flavor, color, …). The vast majority of foods today contain additives that have been added throughout the production and handling process, with the aim of optimizing their function of feeding and nourishing (safe, hygienic foods, …) and their qualities of service (durable, comfortable, affordable, attractive, …).

The nutrition , which starts after the intake of food, consisting of a set of physiological processes (digestion, absorption, metabolism, …), through which the body uses, transformed and incorporated into their structures a number of substances which receives from the medium external with food.

Through nutrition, we obtain energy, build and repair organic structures, and regulate metabolism. In short, we are talking about making life possible and maintaining it, with which we enter fully into the intimate relationship of eating habits with health.

→ Food contains nutrients.

The functions of nutrients in the body:

Each nutrient has its own functions, so that the diet must be complete and balanced. We will see how some provide heat and energy, others regulate bodily processes and others provide substrates for the growth of the organism.

Functions of carbohydrates:

We differentiate between simple carbohydrates (or fast absorption) and complex carbohydrates (or slow absorption), and we can say that its main function is to provide energy for cells.

  • Simple carbohydrates are found in fruits, milk, honey, and sugar and their derivatives. The most common forms are glucose, galactose, sucrose and lactose.
  • Complex carbohydrates are present in legumes, pasta, bread, cereals, flours, rice, potatoes, sweet potatoes, … and in foods rich in vegetable fibers.

The last and resulting product of the digestion of carbohydrates is glucose, which is the nutrient used by the body’s cells to produce and burn energy. Certain groups of cells, such as neurons, liver cells, or blood cells, under normal conditions, can only use glucose to stay alive and function.  

Similarly, it is preferable to obtain glucose from complex carbohydrates and not so much from simple carbohydrates, since the latter, after their quick digestion, very easily release glucose in the blood and stimulate the production of insulin that, in turn, it induces the creation of fat in body tissues and increases appetite.

It is important that, if we follow a diet to control diabetes or body weight, we put aside the daily consumption of foods that contain simple carbohydrates (sweets, …) and moderate the consumption of fruit to two servings per day, trying not to eat it on an empty stomach or in the form of juices.

Fat functions:

They are the carriers of fat-soluble vitamins (A, D, E, K) and are essential for the proper functioning of the immune system, the hormonal system and the nervous system, in addition to being a reserve or long-term energy source.

It is possible to differentiate between saturated fats (present in terrestrial animals and their derivatives) and unsaturated fats (present in marine animals such as blue fish and containing Omega-3 essential oils). In the vegetable kingdom (nuts, seeds, cereal germs and legumes) we also find unsaturated or polyunsaturated fats rich in Omega-6 essential oils.

These oils, which are considered heart-healthy and essential for the proper functioning of the nervous system, the circulatory system and the skin, should be consumed in moderation.

Protein functions:

The proteins , which have a structural or plastic function, are the most important nutrients in creating and maintaining skeletal muscle structure, internal organs, and hair and nails. Its quality or biological value is measured by its ability to drive growth. They are regulators of infinity of vital functions, reason why great part of the biological material is of a protein nature (enzymes, immunoglobulins, neurotransmitters, …).

We can find them in eggs, meats, fish, legumes, cereals and some vegetables. The World Health Organization recommends that only 25% of the proteins we eat be of animal origin, and that the other 75% come from plant foods. For this reason, the adequate consumption of legumes, cereals and nuts will allow us to obtain quality proteins, with less saturated fat and less cholesterol than food of animal origin, with which we will contribute to preventing certain cardiovascular diseases and obesity.

Vitamin functions:

The vitamins , which do not provide energy or calories themselves, perform specific functions in the body like catalyze chemical reactions and are essential for metabolism.

Vitamins A, D, E and K are fat soluble and require fat to pass from the intestinal tract to the bloodstream. They are easily stored in the body and can become toxic in high doses, especially A and D.

The water-soluble vitamins of vitamin B and C complexes are easily eliminated in the urine, in case there is an excess in the body. As they are not easily stored in the body, it is convenient to take them daily. They are generally not toxic, except in very high doses.

Natural sources of vitamins:

  • Vitamin E: Oils and vegetables.
  • Vitamin A: Egg yolk, dairy products, pumpkin seeds and some fruits and vegetables.
  • Vitamin C: Citrus, vegetables, strawberries, kiwi, broccoli, melon, …
  • Vitamin D: Egg yolk, sunlight, cheese and yogurt.
  • Vitamin B1: Yeast, liver, whole grains, beef, spinach and pork.
  • Vitamin B2: Vegetables, milk, liver and legumes in general
  • Vitamin K: Vegetables and vegetable oils.
  • Vitamin B6: Cereals and egg yolk.
  • Folic acid: Fruits, liver and vegetables.
  • Pantothenic Acid: Meat, milk and vegetables.
  • Biotin: Egg, milk and cereals.
  • Niacin: Liver, meat, fish, legumes and nuts such as peanuts.

Functions of minerals:

The minerals are inorganic compounds found in the soil, rocks and water, and are very important for the proper functioning of the body. One of its main functions is to act as catalysts in the regulation of muscle contractions and in the transmission of nerve impulses, in addition to participating in the digestion and metabolization of food.

  • The iron, which is central to the transport of oxygen and in the process of cellular respiration, is found in meat, fish, eggs and food non – animal (lentils, peas and spinach, although it is an iron low absorption). To absorb this iron we have to take a lot of vitamin C, so if we do not eat animal products, we must include vegetables that contain a lot of vitamin C, such as citrus and kiwi, in our diet.
  • The zincparticipates in over 200 chemical reactions at the cell level and is involved in virtually all body systems maintenance and regulation. It is one of the most important minerals for hair. Fortunately, it is present in most food groups, so it is difficult to make a diet low in zinc. Foods of animal origin with a higher concentration of zinc are meat, fish, shellfish and eggs. It is advised that, whenever we can, we cook them in the oven. In this way, we will eliminate a significant percentage of the fats they may contain. We can also find zinc in vegetables such as asparagus, figs, aubergines, celery or potatoes.
  • The copperfavors the blood vessels more flexible and that the blood circulate better. It is present in foods such as cocoa, mushrooms, legumes, nuts, liver and seafood.
  • The magnesiumplays an important role in metabolizing proteins, and can be found in fruits (banana and avocado), legumes, nuts, whole grains and vegetables. Closely related to the muscles and balances adrenal function, PH levels and stress.
  • The calcium, which is closely linked to magnesium, plays an important structural role in our body because it is an integral part of bones and teeth. However, for the proper absorption of calcium by the bone system, the presence of vitamin D is necessary, which as we have seen previously can be obtained from sunlight or from foods such as egg yolk or dairy products.

Water functions:

It is the essential nutrient par excellence. There is no life without the intake of water from the outside. It is the major constituent of body structure, and contributes to regulating temperature, respiration, skin, and blood pressure through the heart and kidneys. In addition, it contributes to the purification of blood.

It is recommended to drink between 1.5 and 2 liters of water a day, regardless of whether it is taken with or without meals. A good way to increase water consumption is to take it in the form of toning or relaxing infusions. If we are on a diet for weight control or diabetes, we must do without sugar and honey.

Functions of dietary fiber: 

The fiber is the part that can not be digested and absorbed many plant foods. Most of the vegetable fibers, called “soluble” or “soft”, are modified in the large intestine or in the colon, thus undergoing partial digestion by microorganisms in the intestinal flora. As a result they release certain products beneficial to the colon and the immune system, since it keeps the cells of the intestine in good health.

Vegetable fibers have a number of  benefits for the body :

  • Increased stool volume and intestinal transit, as they have the ability to retain water and are useful against constipation.
  • Ability to absorb substances that are retained between the fiber meshes and will be expelled with the faeces: cholesterol, bile acids, fats and various harmful substances. In return, it should be noted that they also retain proteins, vitamins and minerals (calcium, iron, magnesium and zinc) that will be eliminated in the faeces. For this reason, fiber intake must be balanced, or else you could fall into a state of malnutrition.
  • Decreased rate of intestinal absorption. It is useful to control diabetes, since glucose is absorbed more slowly.

The recommendations in cases of diabetes, high cholesterol or eating habits to control weight, are in a contribution of 30-50 grams of dietary fiber per day. It will be enough to take bread and whole grains and make the normal contribution of fruits (2 servings) and vegetables (2-3 servings) per day, in addition to 2-3 servings of legumes per week.

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