Vitamins / Витамины
Vitamins are a group of organic substances required in our diets in small amounts for growth and nutrition. They are usually found in foodstuffs or taken as supplements. Yet vitamins probably present a wider gap between myth and reality in the layman’s understanding than almost any other area of our diet. Most people have a recognition that Vitamin C prevents scurvy, that Vitamin A is found in fish-liver oils, or that Vitamin D is found in dairy products; many people believe that Vitamin E preserves youth and prevents sterility, or that Vitamin C can present colds and cancer. Beyond this, however, there is still considerable ignorance and widespread myth. The reality behind the common practice of taking vitamin supplements is less dramatic, although vitamins do represent an important component of the necessary human diet.
The word vitamin was formed from the Latin word «vita» («life») and the Greek word «amine», because 19th century scientists believed that they were formed only from amino acids. Amino acids are the twenty essential code elements which arrange themselves in varied sequences or chains to form complex proteins, the basic foodstuff of life. These organic acids (containing the essential ingredient NH2), in conjunction with the nucleic acids (DNA material being composed of the four bases adenine, guanine thymine and cytosine), «translate» the genetic instructions from the DNA of the chromosome to the RNA transcript, and in turn transfer these instructions from the transcript to proteins.
If proteins are the building blocks of life, then amino acids are the building blocks of proteins. Plant cells form amino acids from the compounds which the plant draws up from the ground, such as the nitrates and ammonia salts. Animals, however, cannot perform this conversion of simple inorganic substances to amino acids, so they must ingest them in the form of food — with herbivorous animals consuming plant proteins in vegetables and carnivorous animals consuming animal proteins in the bodies of their prey.
Vitamins are essential aids in many body processes, converting food the energy, building and maintaining cells, and other functions.
Vitamins can thus be looked at as a crucial ingredient in a the long-term maintenance of health. Vitamins come in two main forms — water soluble and fat soluble. The fat soluble vitamins, including A, D E, and K, «are absorbed by the body with the aid of fat and then stored in body fat». Because they are stored in this way, we do not need to take these vitamins daily, and it is usually possible to maintain adequate amounts in the body through a normal, well-balanced diet. But for the same reason, it is possible to overdose on these vitamins by taking too many as supplements, in which case they can build up to toxic levels and actually cause harm to the person taking them.
The water soluble vitamins, including Vitamin C and all of the B complex vitamins, are «used up quickly or excreted in urine and perspiration; they are not stored and should be consumed daily. They break down quickly and can be partially lost through premature harvesting, long and improper storage, processing, overcooking, and cooking in water». The high amounts of both water-soluble and fat-soluble vitamins found in raw vegetables and fruits are often lost when they are processed, with a few exceptions such as carrots, which actually gain in vitamin A by being cooked.
The best sources of the different vitamin groups are now well-known. Vitamin A, including retinol and «provitamin caretenoids,» is found in liver, butter, whole milk, cheese and egg yolks (retinol) and in carrots, leafy greens, sweet potatoes, pumpkins, cantaloupes, and so on (provitamin caretenoids). Vitamin A is extremely important in formation and maintenance of skin and mucous membranes, in visual functions, and in bone and tooth development. A deficiency of Vitamin A can cause impaired growth, nigh-blindness, diarrhea, and increased mortality in the worst cases. Experiments in giving large Vitamin A supplements for malnourished children have had mixed results; some reported a reduction in infant and child mortality, but a recent study of Sudanese children between 9 and 72 months found little difference in a test group that was given megadoses of A (200,000 units), and a placebo group that was given only small amounts of Vitamin E.
Vitamin D (calciferol), found mostly in fortified dairy products but also in fish oils an egg yolks, is particularly important for hardening of bones and teeth, and aiding in the intestine’s absorption of calcium. Deficiencies of D can cause rickets in children and more rarely, oseomalacia in adults; overdoses are known to cause retarded growth, kidney damage and calcium deposits in the soft tissues. Vitamin E (Tocopherol), is found in vegetable oil, green leafy vegetables, wheat germ, egg yolk, butter, and liver. It functions as an «antioxidant» for other vitamins, preventing C and A and other fatty-acid proteins from being burnt up prematurely; in this way it helps prevent cell-membrane damage. Most experts believe that Vitamin E deficiency can only occur in extreme causes of malnutrition, but this doesn’t mean that supplements might not be useful. One recent study found that Vitamin E-rich blood helped to prevent angina (cardiovascular distress), for reasons not yet understood.
The B vitamin group is very important. B1 or thiamin, found in meats, whole grains and nuts, serves in carbohydrate metabolism and production of ribose for RNA and DNA. B2 or Riboflavin, in liver, milk, cheese, meat and fortified grains, functions as a coenzyme to help cells use oxygen to get energy from food. B6 or pyroxidine, found in meats, shellfish, whole grains and vegetables, also serves as a coenzyme in protein metabolism. B12, found in the same foods and in milk products, serves as a coenzyme in nucleic acid synthesis and development of red blood cells. Deficiencies of the B group can cause anemia, skin problems and other diseases.
Other vitamins include niacin, folacin (folic acid), biotin, and pantothenic acid, all of which serve as coenzymes to help synthesize fat, form vital chemicals in the life processes, or assist in energy metabolism for the body processes. Some typical symptoms of deficiency are fatigue, depression, or anemia. Recently, it has been found that Vitamin K, a fat-soluble substance, is essential in the blood-clotting process, and it is hoped that it can be applied to treatment of hemophilia, wound or surgery recovery, and other medical problems.
As a group, vitamins are often confused with the many hundreds of minerals (inorganic substances) that are also need for basic growth and maintenance functions of the body. Like vitamins, most minerals can also be found in foods, but shortages of minerals are also possible. There have also been unproven claims for vitamins in general, such as that supplements increase children’s IQ. Probably the greatest confusion exists about Vitamin C (ascorbic acid), a substance found in many vegetables and fruits, and needed for holding body cells together, healing wounds and broken bones, and resisting infection. Many extravagant claims, such as curing cancer and preventing common colds, have been made for Vitamin C. While some evidence exists of side-benefits, long-term studies have failed to give conclusive evidence that C can produce miracles. Like other water-soluble vitamins, however, C is easily depleted from the body, and any diet without sufficient C from fresh fruits and vegetables will need supplements.
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