Any of the organic compounds that the body needs for metabolism, for health protection, and for proper growth in the body. children. Las vitaminas también participan en la formación de hormonas, células sanguíneas, sustancias químicas del work nervioso y material genético.
The various vitamins are not related chemically, and most of them have a different physiological action. They generally act as catalysts, combining with proteins to create metabolically active enzymes that in turn produce important chemical reactions throughout the body. Without vitamins, many of these reactions would take longer to occur or would stop altogether. However, there is still a long way to go to get a clear picture of the intricate ways that vitamins work in the body.
The 13 vitamins identified are classified according to their ability to dissolve in fat or water. The fat-soluble vitamins, A, D, E, and K, are often eaten with foods that contain fat, and because they can be stored in body fat, they don't need to be taken every day. The water-soluble vitamins, the eight of group B and vitamin C, cannot be stored and therefore must be consumed frequently, preferably daily (with the exception of some B vitamins, as we will see later).
The body can only make vitamin D; all others must be ingested through diet. Lack gives rise to a wide range of metabolic and other dysfunctions. A well-balanced diet contains all the necessary vitamins, and most people who follow such a diet can correct any previous vitamin deficiencies. However, people who follow special diets, who suffer from intestinal disorders that prevent normal absorption of nutrients, or who are pregnant or breastfeeding, may need special vitamin supplements to support their metabolism.
Aside from these real needs, there is also a popular belief that vitamins provide a remedy for many illnesses, from colds to cancer; but in reality the body quickly eliminates almost all these preparations without absorbing them. Also, fat-soluble vitamins can block the effect of other vitamins and even cause severe poisoning if taken in excess.
Vitamin A is a pale yellow primary alcohol derived from carotene. It affects the formation and maintenance of the skin, mucous membranes, bones and teeth, sight and reproduction. One of the first symptoms of failure is night blindness (difficulty adapting to the dark). Other symptoms are excessive dryness of the skin; lack of secretion of the mucous membrane, which produces susceptibility to bacterial invasion, and dry eyes due to the malfunction of the tear duct, an important cause of blindness in children from underdeveloped countries.
The body gets vitamin A in two ways. One is by making it from carotene, a vitamin precursor found in vegetables like carrots, broccoli, squash, spinach, cabbage, and sweet potatoes. The other is by absorbing it already in the list of organisms that eat vegetables. Vitamin A is found in milk, butter, cheese, egg yolk, liver, and fish liver oil. Too much vitamin A can interfere with growth, stop menstruation, damage red blood cells, and lead to rashes, headaches, nausea, and jaundice.
Also known by the name of vitamin B complex, they are fragile substances, soluble in water, several of which are especially important for metabolizing carbohydrates.
La tiamina o vitamina B1, una sustancia cristalina e incolora, actúa como catalizador en el metabolismo de los hidratos de carbono, permitiendo metabolizar el ácido pirúvico y haciendo que los hidratos de carbono liberen su energía. La tiamina también participa en la síntesis de sustancias que regulan el work nervioso. La insuficiencia de tiamina produce beriberi, que se caracteriza por debilidad muscular, inflamación del corazón y calambres en las piernas, y, en casos graves, incluso ataque al corazón y muerte.
Many foods contain thiamine, but few provide it in significant amounts. The foods richest in thiamine are pork, organ meats (liver, heart and kidneys), brewer's yeast, lean meats, eggs, green leafy vegetables, whole or enriched cereals, wheat germ, berries, nuts and legumes.
Grinding cereals removes the part of the grain that is richest in thiamine, hence the probability that white flour and refined white rice lack this vitamin. The widespread practice of fortifying flour and cereals has partly eliminated the risk of thiamine deficiency, although it still occurs in nutritionally deficient alcoholics.
Riboflavin or vitamin B2, like thiamine, acts as a coenzyme, that is, it must be combined with a portion of another enzyme to be effective in the metabolism of carbohydrates, fats and especially in the metabolism of the proteins involved. in the transport of oxygen.
It also acts in the maintenance of mucous membranes. Riboflavin deficiency can be complicated by a deficiency of other B vitamins. Its symptoms, not as defined as those of thiamine deficiency, are skin lesions, particularly near the lips and nose, and sensitivity to skin. light. The best sources of riboflavin are liver, milk, meat, dark green vegetables, enriched and whole cereals, pasta, bread, and mushrooms.
Nicotinamide or vitamin B3, a vitamin of the B complex whose structure responds to the amide of nicotinic acid or niacin, works as a coenzyme to release energy from nutrients. It is also known as vitamin PP. Insufficient niacin or nicotinic acid produces pellagra, the first symptom of which is a rash similar to a sunburn where the skin is exposed to sunlight.
Otros síntomas son lengua roja e hinchada, diarrea, confusión mental, irritabilidad y, cuando se ve afectado el work nervioso central, depresión y trastornos mentales. Las mejores fuentes de niacina son: hígado, aves, carne, salmón y atún enlatados, cereales enteros o enriquecidos, guisantes (chícharos), granos secos y frutos secos. El cuerpo también fabrica niacina a partir del aminoácido triptófano.
Niacin overdoses have been used experimentally in the treatment of schizophrenia, although no trials have shown their efficacy. In large quantities it reduces the levels of cholesterol in the blood, and has been widely used in the prevention and treatment of arteriosclerosis. Large doses over long periods can be harmful to the liver.
Pyridoxine or vitamin B6 is necessary for the absorption and metabolism of amino acids. It also acts in the use of fat in the body and in the formation of red blood cells. Pyridoxine insufficiency is characterized by skin changes, cracks at the corners of the lips, a depapillated tongue, seizures, dizziness, nausea, anemia, and kidney stones. The best sources of pyridoxine are whole grains (not fortified ones), cereals, bread, liver, avocado, spinach, green beans (green beans), and bananas. The amount of pyridoxine required is proportional to the amount of protein consumed.
La cobalamina o vitamina B12 también se conoce como cianocobalamina, una de las vitaminas aisladas más recientemente, y es necesaria en cantidades ínfimas para la formación de nucleoproteínas, proteínas y glóbulos rojos, y para el funcionamiento del work nervous.
Cobalamin deficiency is often due to the stomach's inability to produce a glycoprotein (intrinsic factor) that helps absorb this vitamin. The result is pernicious anemia, with the characteristic symptoms of poor red blood cell production, defective synthesis of myelin (nerve sheath), and loss of the epithelium (membranous covering) of the intestinal tract. Cobalamin is obtained only from animal sources: liver, kidneys, meat, fish, eggs, and milk. Vegetarians are advised to take vitamin B12 supplements.
Other vitamins of group B
Folic acid or folacin is a necessary coenzyme for the formation of structural proteins and hemoglobin; its insufficiency in humans is very rare. Folic acid is effective in treating certain anemias and psilosis.
It is found in the organ meats, green leafy vegetables, legumes, nuts, whole grains, and brewer's yeast. Folic acid is lost in foods stored at room temperature and during cooking. Unlike other water-soluble vitamins, folic acid is stored in the liver and does not need to be ingested on a daily basis.
Pantothenic acid, another B vitamin, plays a yet undefined role in the metabolism of proteins, carbohydrates, and fats. It is abundant in many foods and is also manufactured by intestinal bacteria.
Biotin, another B vitamin that is also synthesized by intestinal bacteria and is widespread in food, participates in the formation of fatty acids and in the release of energy from carbohydrates. Its insufficiency in humans is unknown.
Vitamin C (ascorbic acid)
Vitamin C is important in the formation and preservation of collagen, the protein that supports many body structures and plays a very important role in the formation of bones and teeth. It also favors the absorption of iron from foods of plant origin.
Scurvy is the classic manifestation of severe ascorbic acid deficiency. Its symptoms are due to the loss of the cementing action of collagen, and among them are hemorrhages, loss of teeth and cellular changes in the bones of children. The claim that massive doses of ascorbic acid prevent colds and flu has not been derived from carefully controlled experiences.
However, other experiments have shown that ascorbic acid prevents the formation of nitrosamines, compounds that have produced tumors in laboratory animals and may produce them in humans.
Although unused ascorbic acid is rapidly excreted in the urine, long and prolonged doses can lead to bladder and kidney stone formation, interference with the effects of anticoagulants, destruction of vitamin B12, and loss of calcium in the bones. Sources of vitamin C include citrus fruits, fresh strawberries, grapefruit, pineapple, and guava. Good plant sources are broccoli, Brussels sprouts, tomatoes, spinach, cabbage, green bell peppers, cabbage, and turnips.
It is necessary for the normal formation of bones and for the retention of calcium and phosphorus in the body. It also protects teeth and bones against the effects of low calcium intake, making more effective use of calcium and phosphorus. Also called 'solar vitamin', vitamin D is obtained from egg yolk, liver, tuna and milk enriched with vitamin D.
It is also made in the body when sterols, found in many foods, travel to the skin and receive radiation from the Sun. Vitamin D insufficiency, or rickets, occurs rarely in tropical climates where there is an abundance of sunlight, but there was a time when it was common among children in little sunny cities before they started using milk enriched with this vitamin.
Rickets is characterized by deformity of the rib cage and skull and bowed legs, all caused by poor absorption of calcium and phosphorus in the body. Because vitamin D is fat soluble and stored in the body, excessive consumption can cause vitamin poisoning, kidney damage, lethargy, and loss of appetite.
The role of vitamin E in the human body has not yet been clearly established, but it is known to be an essential nutrient in more than twenty vertebrate species. This vitamin participates in the formation of red blood cells, muscles and other tissues and in the prevention of the oxidation of vitamin A and fats.
It is found in vegetable oils, wheat germ, liver, and green leafy vegetables. Although vitamin E is popularly recommended for a wide variety of conditions, there is no substantial evidence to support these claims. Although it is stored in the body, it appears that overdoses of vitamin E have fewer toxic effects than those of other fat-soluble vitamins.
Vitamin K is necessary primarily for blood clotting. Helps the formation of prothrombin, an enzyme necessary for the production of fibrin in coagulation. The richest sources of vitamin K are alfalfa and fish liver, which are used to make preparations with concentrations of this vitamin.
Dietary sources include all green leafy vegetables, egg yolks, soy or soybean oil, and liver. For a healthy adult, a normal diet and intestinal bacterial synthesis is usually sufficient to supply the body with vitamin K and prothrombin. Digestive disorders can cause poor absorption of vitamin K, and therefore deficiencies in blood clotting.
The group of carbohydrates consists mainly of sugar, starch, dextrin, cellulose and glycogen, substances that constitute an important part of the diet of humans and many animals. The simplest are simple sugars or monosaccharides, which contain an aldehyde or ketone group; the most important is glucose. Two monosaccharide molecules joined by an oxygen atom, with the elimination of a water molecule, produce a disaccharide, the most important being sucrose, lactose and maltose.
Starch and pectin, a curdling agent, are used in the preparation of food for man and livestock. Gum arabic is used in demulcent medicines. Agar, a component of some laxatives, is used as a thickening agent in food and as a medium for bacterial culture; also in the preparation of adhesive materials, sizing and emulsions.
Hemicellulose is used to modify paper during its manufacture. Dextrans are polysaccharides used in medicine as volume expanders of blood plasma to counteract acute concussions. Another carbohydrate, heparin sulfate, is a blood thinner.
They provide a large amount of energy in most human diets. They are burned during metabolism to produce energy, releasing carbon dioxide and water.
There are two types of carbohydrates: starches, which are found mainly in cereals, legumes and tubers, and sugars, which are present in vegetables and fruits. Carbohydrates are used by cells in the form of glucose, the body's main fuel.
The carbohydrates in which most of the nutrients are found are the so-called complex carbohydrates, such as unrefined cereals, tubers, fruits and vegetables, which also provide proteins, vitamins, minerals and fats.
Fats are important in the diet as a source of energy, since they produce 9 kcal per gram. In developed countries, 40% or more of total energy consumption usually comes from fat. It is a higher percentage than what is considered advisable for health, excessive fat consumption is associated with obesity, heart and gallbladder diseases and some types of cancer. The nutritional lines, therefore, recommend not to ingest more than 30% of energy through fat.
In less developed countries, fats can provide less than 15% energy, a level of consumption in which it is difficult to eat enough to meet energy needs. Fat is also important for the absorption of the fat-soluble vitamins A, D, E and K. Much of the flavor of food is contained in fat.
To help people reduce their fat intake, a variety of low-fat products have been created to partially or fully replace butter and margarine (containing 80-82% fat) in the diet. Spreads are made with melted cream and vegetable oil and contain 72-75% fat, while the same low-fat products are mainly vegetable oils that contain 60-70% fat, and can be used for the kitchen just like butter or margarine.
Low fat (37-40%) and very low fat (20-25%) contain milk fat and vegetable oils and are not suitable for cooking. Those that are very low in fat (5%) are made using a fat substitute such as Simplesse, a modified protein, or Olestra (both are trademarks), a sugary polyester that is not digested.
Fats are divided into saturated and unsaturated, depending on whether the chemical bonds between the carbon atoms of the molecules contain all the hydrogen atoms that they can have (saturated) or have capacity for more atoms (unsaturated), due to the presence of double or triple bonds. Saturated fats are generally solid at room temperature; unsaturated and polyunsaturated are liquid. Unsaturated fats can be converted to saturated fats by adding hydrogen atoms.
When solid saturated fats are added to the diet, the amount of cholesterol in the blood increases, but if the solid fats are replaced by liquid unsaturated fats or oils (specifically the polyunsaturated type), the amount of cholesterol decreases.
Although rarer than carbohydrates, fats produce more than twice the energy. As it is a compact fuel, fats are stored very well to be used later in case the carbohydrate intake is reduced.
Lack of all vitamins.
This has a strong impact on enzymatic activity; it is particularly noticeable at the time of re-nutrition, when demand is sharply increased.
Retinol deficiency is particularly important, whose contribution is lacking due to low protein intake. The provision of carotene, however, does not compensate either, because the intestine converts little into retinol, with which twilight vision falls (less rhodopsin), colors are poorly recognized, there are Bitot's spots and xerophthalmia (dry atrophy of ocular conjunctiva ).
In our setting, however, keratomalacia and corneal ulcer are not frequent. As less retinoic acid is also formed, less mucus is formed for sebaceous secretions and local cutaneous immunity is lowered; this is aggravated by epithelial cell atrophy and increased keratinization, which occludes the hair follicles.
In primary malnutrition, the lack of thiamine blocks the conversion of pyruvic acid. In developing countries the most conspicuous clinical manifestation is beriberi. Thiamine is also necessary to metabolize branched-chain amino acids.
The lack of riboflavin affects the synthesis of flavo proteins, necessary for deamlination, the oxidation of fatty acids and the respiratory chain. This is aggravated by the lack of supply of niacin, which also acts as an electron transporter and cannot be compensated by the metabolism of tryptophan, since it is an essential amino acid and its contribution is also diminished.
The lack of pyridoxine compromises the operation of a large number of enzymatic reactions. On the other hand, the deficiency of folates is very frequent, which are essential for the synthesis of the nuclei of all cells, which can be witnessed by the diagnosis of macro-sciatic anemia. The cobalamin deficiency is compensated by strong hepatic reserves by diffusion absorption and by the low contribution of intrinsic factor.
Menadione deficiency is compensated by intestinal bacterial synthesis; but in the newborn there is little contribution from breastfeeding, this flora is lacking and a tendency to hemorrhage appears.
A hiccupthesis To explain the action of tocopherols, he postulates that the phytyl chain interacts with the unsaturated fatty acids of the membranes.