Introduction: VITAMIN C (ASCORBIC ACID)
Vitamin C is one is an essential nutrient for mammals, it is found in most fruits and vegetables, as well as being essential for the growth and health of children. ABC of the baby. It is listed as the star vitamin.
History
In 1937, the Nobel Prize in Chemistry was awarded to Walter Haworth for his work in determining the structure of ascorbic acid, (shared with Paul Karrer for his work on vitamins) and the Nobel Prize in medicine was awarded to Albert von Szent -Györgyi Nagyrápolt for his studies about the biological functions of ascorbic acid. A food additive is any substance that, without constituting itself a food or possessing nutritional value, is intentionally added to food and beverages in minimum quantities in order to modify its organoleptic characteristics or facilitate or improve its production or preservation process.
The discovery of vitamin C is associated with scurvy, a disease that was first seen among those who made long trips by sea. In 1497, Vasco da Gama described the symptoms of scurvy among sailors on their historic voyage from Europe to India, bordering the southern tip of Africa; More than half of its crew died due to the disease. Gradually it became clear that scurvy attacked only those who did not consume fresh food. In 1747 James Lind, from Scotland, showed that the disease could be avoided or cured by eating citrus fruits. This finding led to the introduction of fresh foods, especially citrus fruits in sea rations. From there scurvy was less common.
However, in the 19th century, scurvy began to be found among children under one year old who received canned milk, which had recently been introduced, instead of breast milk or fresh cow's milk. Preserved milk contained enough carbohydrates, fat, protein and minerals, but the heat to process it destroyed vitamin C, and therefore cases of scurvy were verified in children. Later it was discovered that vitamin C was ascorbic acid, which had already been identified.
Biosynthesis
A large majority of animals and plants are able to synthesize vitamin C, through a sequence of 4 enzymatic steps, which convert glucose to vitamin C. The glucose needed to produce ascorbate in the liver (in mammals) is extracted from glycogen This is why the synthesis of ascorbate is a glycolysis-dependent process.
In Reptiles and Birds, biosynthesis is carried out in the Kidneys.
Human beings do not possess the enzymatic ability to produce vitamin C. The cause of this phenomenon is that the last enzyme in the synthesis process, L-gulonolactone oxidase is absent because the gene for this enzyme (Pseudogene ΨGULO) is defective. Mutation is not lethal to the body, because vitamin C is abundant in food sources. It has been detected that species with this mutation (including humans) have adapted a recycling mechanism to compensate for it.
Vitamin C can be absorbed as ascorbic acid and as a dehydroascorbic acid at the level of the oral mucosa, stomach and jejunum (small intestine), then it is transported via the portal vein to the liver and then be taken to the tissues that require it. It is excreted by the kidneys (in the urine), mainly in the form of oxalic acid, only the non-absorbed vitamin is eliminated by feces.
It has been observed that the loss of the ability to synthesize ascorbate is surprisingly parallel to the evolutionary loss of the ability to decrease uric acid. Uric acid and ascorbate are strong reducing agents. This has led to the suggestion that in higher primates, uric acid has assumed some functions of ascorbate. Ascorbic acid can be oxidized in the human body by the acid-ascorbic oxidase enzyme.
Vitamin C is the L-enantiomer of ascorbate, the opposite D-enantiomer has no biological significance. Both forms have the same structural molecule. When L-ascorbate, (which is a strong reducing agent), applies its reducing function, it is converted to its oxidized form, L-dehydroascorbate, which can be reduced back to its active form L-ascorbate by enzymatic action of glutathione.
Properties
Ascorbic acid is a white crystalline substance, very soluble in water. It tends to rust easily. It is not affected by light, but excessive heat destroys it, especially when it is in an alkaline solution. As it is a powerful antioxidant and reducing agent, it can therefore reduce the damaging action of free radicals and is also important for improving the absorption of non-heminic iron in plant-based foods.
Ascorbic acid is necessary for the proper formation and maintenance of intercellular material, especially collagen. In simple terms, it is essential to produce part of the substance that binds the cells, just as the cement binds the bricks. In a person who lacks ascorbic acid, capillary endothelial cells lack normal solidity. They are, therefore, fragile and hemorrhages occur. Similarly, the dentin of the teeth and bone bone tissue do not form well. In addition, this property of cellular fixation explains the poor healing and the slowness in the healing process of the wounds that is seen in people with lack of ascorbic acid.
It is a common belief, also mentioned by some scientists, that abundant doses of vitamin C prevent and reduce the symptoms of the common cold (coryza). This statement has not been proven. An extensive study suggests a modest reduction in the severity of symptoms in those who take vitamin C medicinally, but the vitamin did not prevent colds. It is not advisable to take very high therapeutic doses of vitamin C for long periods.
Food sources
The main sources of vitamin C in most diets are fruits, vegetables and various types of leaves (Photo 14). In nomadic tribes, milk is often the main source. Bananas and bananas are the only staple food that contains adequate portions of vitamin C. Dark green leaves, such as amaranth and spinach contain much more vitamin C than pale leaves such as cabbage and lettuce. Root vegetables and potatoes contain small but useful amounts. Young corn provides some ascorbic acid, as well as sprouted cereals and legumes. Animal products (meat, fish, milk and eggs) have small quantities.
As heat easily destroys vitamin C, prolonged cooking of any food can destroy a large amount of the vitamin C it contains. Ascorbic acid is measured in milligrams of pure vitamin.
Function
In humans, vitamin C is a potent antioxidant, acting to reduce oxidative stress; a substrate for ascorbate peroxidase, as well as an enzymatic cofactor for the biosynthesis of important biochemicals. This vitamin acts as an electron donor agent for 8 different enzymes:
Three enzymes participate in the hydroxylation of collagen. These reactions add hydroxyl groups to the proline or lysine amino acids in the collagen molecule (proline hydroxylase and lysi hydroxylase pathway), thereby allowing the collagen molecule to assume its triple helix structure. In this way, vitamin C becomes an essential nutrient for the development and maintenance of scar tissue, blood vessels, and cartilage.
Two enzymes are necessary for carnitine synthesis. This is necessary for the transport of fatty acids to the mitochondria for the generation of ATP.
The three remaining enzymes have functions in:
Participation in the biosynthesis of norepinephrine from dopamine, through the enzyme dopamine-beta-hydroxylase.
Another enzyme adds amide groups to peptide hormones, greatly increasing its stability.
Another modulates the metabolism of tyrosine.
The biological tissues that accumulate more than 100 times the blood level of vitamin C, are the adrenal glands, pituitary, thymus, corpus luteum, and the retina. Those with 10 to 50 times the concentration present in the plasma include the brain, spleen, lung, testicles, lymph nodes, small intestine mucosa, leukocytes, pancreas, kidney and salivary glands.
Vitamin C helps the development of teeth and gums, bones, cartilage, iron absorption, growth and repair of normal connective tissue (softer skin, by the union of cells that need this vitamin to join), to the Collagen production (acting as a cofactor in the hydroxylation of the amino acids lysine and proline), fat metabolization, wound healing. Its lack causes scurvy, this vitamin is also a potentiating factor for the immune system although some studies cast doubt on the latter activity of vitamin C. White blood cells contain 20 to 80 times more vitamin C than blood plasma, and the same strengthens the cytotoxic capacity of neutrophils (white blood cells).
Vitamin C is essential for the development and maintenance of the body, so its consumption is mandatory to maintain good health. Vitamin C serves to: Prevent premature aging (protect connective tissue, the "skin" of blood vessels).
It facilitates the absorption of other vitamins and minerals.
Antioxidant
Avoid degenerative diseases such as arteriosclerosis, cancer, Alzheimer's disease. Avoid heart disease. From the discoveries of Linus Pauling it was asserted that vitamin C reinforced the immune system and prevented the flu, but research carried out in the 1990s seems to refute this theory and, in any case, has shown that excessive consumption (as opposed to what was recommended by Pauling and his followers) of vitamin C supplements are not recommended, because, among other things, excessive consumption can cause gastrointestinal disturbances.
Needs in humans
Opinions about human needs differ greatly. It seems clear that up to 75 mg daily is needed for the body to remain fully saturated with vitamin C. However, people seem to stay healthy with intakes as low as 10 mg per day. Figures of 25 mg for adults, 30 mg for adolescents, 35 mg in pregnancy and 45 mg during breastfeeding appear to be reasonable amounts.
Lack
Scurvy and other clinical manifestations due to a lack of vitamin C are described in Chapter 19. Scurvy is currently not a predominant disease. Outbreaks have occurred in famine areas and recently in several refugee camps in Africa. In its early stages, vitamin C deficiency can cause bleeding gums and slow wound healing.
Myth or truth: Once you have read all this content it is important to recognize that you should have an adequate consumption of fruits or supplements of this vitamin, but being water soluble this vitamin is not really stored and that is why we must maintain a constant intake, which can help our immune system to defenses that is why we should consume it but not excess.
Bibliography:
• Dr. Alejandro Schroeder - Forever Living Products Vitamin-C - https://www.ecured.cu/Vitamina_C
• http://www.fao.org/3/w0073s/w0073s0f.htm