BIOCHEMISTRY OF WATER SOLUBLE VITAMINS: CLASSIFICATION, STRUCTURE, COENZYME FORMS, BIOLOGICAL ACTION, DAY NECESSITY, SOURSES.

HYPO- AND HYPERVITAMINOSIS.

Vitamins are nutrients required in tiny amounts for essential metabolic reactions in the body. The term vitamin does not include other essential nutrients such as dietary minerals, essential fatty acids, or essential amino acids, nor does it encompass the large number of other nutrients that promote health but that are not essential for life.

Vitamins are bio-molecules that act both as catalysts and substrates in chemical reactions. When acting as a catalyst, vitamins are bound to enzymes and are called cofactors. (For example, vitamin K forms part of the proteases involved in blood clotting.) Vitamins also act as coenzymes to carry chemical groups between enzymes. (For example, folic acid carries various forms of carbon groups–methyl, formyl or methylene–in the cell.)/

Until the 1900s, vitamins were obtained solely through food intake. Many food sources contain different ratios of vitamins. Therefore, if the only source of vitamins is food, changes in diet will alter the types and amounts of vitamins ingested. However, as many vitamins can be stored by the body, short-term deficiencies (which, for example, could occur during a particular growing season) do not usually cause disease.

Vitamins have been produced as commodity chemicals and made widely available as inexpensive pills for several decades,^[2] allowing supplementation of the dietary intake.

Difference from water soluble vitamins: water soluble vitamins are included into coenzymes, don't have provitamins, are not included into the membranes, and hypervitaminoses are not peculiar for them.

With exception of vitamin B₆ and B₁₂, they are readily excreted in urine without appreciable storage, so frequent consumption becomes necessary. They are generally nontoxic when present in excess of needs, although symptoms may be reported in people taking megadoses of niacin, vitamin C, or pyridoxine (vitamin B₆). All the B vitamins function as coenzymes or cofactors, assisting in the activity of important enzymes and allowing energy-producing reactions to proceed normally. As a result, any lack of water-soluble vitamins mostly affects growing or rapidly metabolizing tissues such as skin, blood, the digestive tract, and the nervous system. Water-soluble vitamins are easily lost with overcooking.

Water-soluble vitamins and their characteristics.
Common food sources	Major functions	Deficiency symptoms	Overconsumption symptoms	Stability in foods
Vitamin C (abscorbic acid)
Citrus fruits, broccoli, strawberries, melon, green pepper, tomatoes, dark green vegetables, potatoes.	Formation of collagen (a component of tissues), helps hold them together; wound healing; maintaining blood vessels, bones, teeth; absorption of iron, calcium, folacin; production of brain hormones, immune factors; antioxidant.	Bleeding gums; wounds don't heal; bruise easily; dry, rough skin; scurvy; sore joints and bones; increased infections.	Nontoxic under normal conditions; rebound scurvy when high doses discontinued; diarrhea, bloating, cramps; increased incidence of kidney stones.		Most unstable under heat, drying, storage; very soluble in water, leaches out of some vegetables during cooking; alkalinity (baking soda) destroys vitamin C.
Thiamin (vitamin B1 )
Pork, liver, whole grains, enriched grain products, peas, meat, legumes.	Helps release energy from foods; promotes normal appetite; important in function of nervous system.	Mental confusion; muscle weakness, wasting; edema; impaired growth; beriberi.	None known.		Losses depend on cooking method, length, alkalinity of cooking medium; destroyed by sulfite used to treat dried fruits such as apricots; dissolves in cooking water.
Riboflavin (vitamin B2)
Liver, milk, dark green vegetables, whole and enriched grain products, eggs.	Helps release energy from foods; promotes good vision, healthy skin.	Cracks at corners of mouth; dermatitis around nose and lips; eyes sensitive to light.	None known.			Sensitive to light; unstable in alkaline solutions.
Niacin (nicotinamide, nicotinic acid)
Liver, fish, poultry, meat, peanuts, whole and enriched grain products.	Energy production from foods; aids digestion, promotes normal appetite; promotes healthy skin, nerves.	Skin disorders; diarrhea; weakness; mental confusion; irritability.	Abnormal liver function; cramps; nausea; irritability.
Vitamin B6 (pyridoxine, pyridoxal, pyridoxamine)
Pork, meats, whole grains and cereals, legumes, green, leafy vegetables.	Aids in protein metabolism, absorption; aids in red blood cell formation; helps body use fats.	Skin disorders, dermatitis, cracks at corners of mouth; irritability; anemia; kidney stones; nausea; smooth tongue.	None known.			Considerable losses during cooking.

Folacin (folic acid)
Liver, kidney, dark green leafy vegetables, meats, fish, whole grains, fortified grains and cereals, legumes, citrus fruits.	Aids in protein metabolism; promotes red blood cell formation; prevents birth defects of spine, brain; lowers homocystein levels and thus coronary heart disease risk.	Anemia; smooth tongue; diarrhea.	May mask vitamin B12 deficiency (pernicious anemia).	Easily destroyed by storing, cooking and other processing.
Vitamin B12
Found only in animal foods: meats, liver, kidney, fish, eggs, milk and milk products, oysters, shellfish.	Aids in building of genetic material; aids in development of normal red blood cells; maintenance of nervous system.	Pernicious anemia, anemia; neurological disorders; degeneration of peripheral nerves that may cause numbness, tingling in fingers and toes.	None known.
Pantothenic acid
Liver, kidney, meats, egg yolk, whole grains, legumes; also made by intestinal bacteria.	Involved in energy production; aids in formation of hormones.	Uncommon due to availability in most foods; fatigue; nausea, abdominal cramps; difficulty sleeping.	None known.	About half of pantothenic acid is lost in the milling of grains and heavily refined foods.

Thiamin (Vitamin B₁)

Thiamine or thiamin, also known as vitamin B1, is a colorless compound with chemical formula C12H17N4OS. It is soluble in water and insoluble in alcohol.

Thiamine decomposes if heated. Its chemical structure contains a pyrimidine ring and a thiazole ring.Thiamine was first discovered in 1910 by Umetaro Suzuki in Japan when researching how rice bran cured patients of Beriberi. He named it aberic acid. Thiamine diphosphate (ThDP) or thiamine pyrophosphate (TPP) is a coenzyme for pyruvate dehydrogenase, α-ketoglutarate dehydrogenase, branched-chain

Thiamin pyrophosphate

alpha-keto acid dehydrogenase, and transketolase. The first two of these enzymes function in the metabolism of carbohydrates, while transketolase functions in the pentose phosphate pathway to synthesize NADPH and the pentose sugars deoxyribose and ribose. In general, TPP functions as a cofactor for enzymes that catalyze the dehydrogenation (decarboxylation and subsequent conjugation to Coenzyme A) of alpha-keto acids. TPP is synthesized by the enzyme thiamine

pyrophosphokinase, which requires free thiamine, magnesium, and adenosine triphosphate.

Good sources: Thiamine is found naturally in the following foods, each of which contains at least 0.1mg of the vitamin per 28-100g (1-3.5oz): Green peas, Spinach, Liver, Beef, Pork, Navy beans, Nuts, Pinto beans, Soybeans, Whole-grain and Enriched Cereals, Breads, Yeast, and Legumes.

Thiamin functions as the coenzyme thiamin pyrophosphate (TPP) in the metabolism of carbohydrate and in conduction of nerve impulses. Thiamin deficiency causes beri-beri, which is frequently seen in parts of the world where polished (white) rice or unenriched white flour are predominantly eaten.

There are three basic expressions of beriberi: childhood, wet, and dry. Childhood beriberi stunts growth in infants and children. Wet beriberi is the classic form, with swelling due to fluid retention (edema) in the lower limbs that spreads to the upper body, affecting the heart and leading to heart failure. Dry beriberi affects peripheral nerves, initially causing tingling or burning sensations in the lower limbs and progressing to nerve degeneration,

muscle wasting, and weight loss. Thiamine-deficiency disease in North America commonly occurs in people with heavy alcohol consumption and is called Wernicke-Korsakoff syndrome. It is caused by poor food intake and by decreased absorption and increased excretion caused by alcohol consumption.

Riboflavin (Vitamin B₂)

Riboflavin is stable when heated in ordinary cooking, unless the food is exposed to ultraviolet radiation (sunlight). To prevent riboflavin breakdown, riboflavin-rich foods such as milk, milk products, and cereals are packaged in opaque containers. Riboflavin is a component of two coenzymes—flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD)—that act as hydrogen carriers when carbohydrates and fats are used to produce energy. It is helpful in maintaining good vision and healthy hair, skin and nails, and it is necessary for normal cell growth.

Thiamin pyrophosphate

Riboflavin deficiency causes a condition known as ariboflavinosis, which is marked by cheilosis (cracks at the corners of the mouth), oily scaling of the skin, and a red, sore tongue. In addition, cataracts may occur more frequently with riboflavin deficiency. A deficiency of this nutrient is usually a part of multinutrient deficiency and does not occur in isolation. In North America, it is mostly observed in alcoholics, elderly persons with low income or depression, and people with poor eating habits, particularly those who consume highly refined and fast foods and those who do not consume milk and milk products.

Unlike fat-soluble vitamins, water-soluble vitamins are easily lost during cooking and processing. The body does not store excess quantities of most water-soluble vitamins, so foods bearing them must be consumed frequently.

Niacin (Vitamin B₅)

Niacin

Nicotinamide	Nicotinic Acid

Niacin exists in two forms, nicotinic acid and nicotinamide. Both forms are readily absorbed from the stomach and the small intestine. Niacin is stored in small amounts in the liver and transported to tissues, where it is converted to coenzyme forms. Any excess is excreted in urine. Niacin is one of the most stable of the B vitamins. It is resistant to heat and light, and to both acid and alkali environments. The human body is capable of converting the amino acid tryptophan to niacin when needed. However, when both tryptophan and niacin are deficient, tryptophan is used for protein synthesis.

Structure of NAD⁺

There are two coenzyme forms of niacin: nicotinamide adenine dinucleotide (NAD⁺) and nicotinamide adenine dinucleotide phophate (NADP⁺). They both help break down and utilize proteins, fats, and carbohydrates for energy. Niacin is essential for growth and is involved in hormone synthesis.

Pellagra results from a combined deficiency of niacin and tryptophan. Long-term deficiency leads to central nervous system dysfunction manifested as confusion, apathy, disorientation, and eventually coma and death. Pellagra is rarely seen in industrialized countries, where it may be observed in people with rare disorder of tryptophan metabolism (Hartnup's disease), alcoholics, and those with diseases that affect food intake. The liver can synthesize niacin from the essential aminoacid tryptophan, but the synthesis is extremely slow; 60 mg of tryptophan are required to make one milligram of niacin. Dietary niacin deficiency tends to occur only in areas where people eat corn, the only grain low in niacin, as a staple food, and that don't use lime during maize (corn) meal/flour production. Alkali lime releases the tryptophan from the corn so that it can be absorbed in the gut, and converted to niacin.

Niacin plays an important role in the production of several sex and stress-related hormones, particularly those made by the adrenal gland. Niacin, when taken in large doses, increases the level of high density lipoprotein (HDL) or "good" cholesterol in blood, and is sometimes prescribed for patients with low HDL, and at high risk of heart attack. Niacin (but not niacinamide) is also used in the treatment of hyperlipidemia because it reduces very low density lipoprotein (VLDL), a precursor of low density lipoprotein (LDL) or "bad" cholesterol, secretion from the liver, and inhibits cholesterol synthesis.

The main problem with the clinical use of niacin for dyslipidemia is the occurrence of skin flushing, even with moderate doses.

Recommended intake is expressed as milligrams of niacin equivalents (NE) to account for niacin synthesized from tryptophan. High doses taken orally as nicotinic acid at 1.5 to 2 grams per day can decrease cholesterol and triglyceride levels, and along with diet and exercise can slow or reverse the progression of heart disease.

The nicotinamide form of niacin in multivitamin and B-complex tablets do not work for this purpose. Supplementation should be under a physician's guidance.

Pantothenic Acid (Vitamin B₃)

Pantothenic Acid

Pantothenic Acid

Pantothenic acid, also called vitamin B3, is a water-soluble vitamin required to sustain life. Pantothenic acid is needed to form coenzyme-A (CoA), and is critical in the metabolism and synthesis of carbohydrates, proteins, and fats. Its name

is derived from the Greek pantothen meaning "from everywhere" and small quantities of pantothenic acid are found in nearly every food, with high amounts in

whole grain cereals, legumes, eggs, meat, and royal jelly

Pantothenic acid is stable in moist heat. It is destroyed by vinegar (acid), baking soda (alkali), and dry heat. Significant losses occur during the processing and refining of foods. Pantothenic acid is released from coenzyme A in food in the small intestine. After absorption, it is transported to tissues, where coenzyme A is resynthesized. Coenzyme A is essential for the formation of energy as adenosine triphosphate (ATP) from carbohydrate, protein, alcohol, and fat.

Coenzyme A is also important in the synthesis of fatty acids, cholesterol, steroids, and the neurotransmitter acetylcholine, which is essential for transmission of nerve impulses to muscles.

Coenzyme A

Dietary deficiency occurs in conjunction with other B-vitamin deficiencies. Pantothenic acid is used in the synthesis of coenzyme A (abbreviated as CoA). Coenzyme A may act as an acyl group carrier to form acetyl-CoA and other related compounds; this is a way to transport carbon atoms within the cell. The transfer of carbon atoms by coenzyme A is important in cellular respiration, as well as the biosynthesis of many important compounds such as fatty acids, cholesterol, and acetylcholine. Dietary deficiency occurs in conjunction with other B-vitamin deficiencies. In studies, experimentally induced deficiency in humans has resulted in headache, fatigue, impaired muscle coordination, abdominal cramps, and vomiting.

In studies, experimentally induced deficiency in humans has resulted in headache, fatigue, impaired muscle coordination, abdominal cramps, and vomiting.

Biotin (Vitamin B₈)

Biotin

Biotin is a water soluble vitamin and a member of Vitamin B complex.  Also known as Vitamin H, Bios II, Co-enzyme R.  Its natural form is D-biotin.  It was isolated from liver in 1941 by Dr. Paul Gyorgy.

FUNCTION

• co-enzyme in wide variety of body metabolic reactions
• needed for production of energy from carbohydrates, fats and proteins
• needed for interconversions
• essential for maintenance of healthy skin, hair, sweat glands, nerves, bone marrow and glands producing sex hormones

FOOD SOURCE

• Brewer's Yeast
• cheese
• eggs
• maize
• fish, fatty, white
• meats, especially pig liver and kidney
• milk
• oats
• wheat bran
• wheat germ
• wholemeal grains
• unpolished brown rice
• vegetables
• yoghurt

EFFECTIVE WITH

INCREASED INTAKES NEEDED

• by newborn children being fed on dried milk
• during stress situations
• when on antibiotic therapy

USED FOR

• seborrheic dermatitis
• Leiner's Disease
• alopecia (hair falling out in handfuls)
• scalp disease
• skin complaints
• preventing cot death (given to babies)

DESTROYED BY

• leaching into cooking
• drying of milk for baby foods

SYMPTOMS OF DEFICIENCY

In babies:

• dry scaling of the scalp and face
• persistent diarrhea

In adults:

• depression
• diminished reflexes
• fatigue
• hair loss
• increase in blood cholesterol levels
• loss of appetite
• muscular pains
• nausea
• pale, smooth tongue
• sleepiness

DEFICIENCY LEADS TO

• specific anemia
• deficiency may be induced by excessive intake of raw egg whites, which contain the protein Avidin which immobilizes Biotin

SYMPTOMS OF TOXICITY

• toxicity unknown

High quality Vitamin B (Biotin) can be purchased from Global Herbal Supplies

Biotin is the most stable of B vitamins. It is commonly found in two forms: the free vitamin and the protein-bound coenzyme form called biocytin. Biotin is absorbed in the small intestine, and it requires digestion by enzyme biotinidase, which is present in the small intestine. Biotin is synthesized by bacteria in the large intestine, but its absorption is questionable. Biotincontaining coenzymes participate in key reactions that produce energy from carbohydrate and synthesize fatty acids and protein.

Avidin is a protein in raw egg white, which can bind to the biotin in the stomach and decrease its absorption. Therefore, consumption of raw whites is of concern due to the risk of becoming biotin deficient. Cooking the egg white, however, destroys avidin. Deficiency may develop in infants born with a genetic defect that results in reduced levels of biotinidase. In the past, biotin deficiency was observed in infants fed biotin-deficient formula, so it is now added to infant formulas and other baby foods.

Vitamin B₆

Vitamin B₆

Pyridoxal

Pyridoxal, pyridoxamine and pyridoxine are collectively known as vitamin B₆. All three compounds are efficiently converted to the biologically active form of vitamin B₆, pyridoxal phosphate. This conversion is catalyzed by the ATP requiring enzyme, pyridoxal kinase.

Pyridoxal Phosphate

Vitamin B₆ is present in three forms: pyridoxal, pyridoxine, and pyridoxamine. All forms can be converted to the active vitamin-B₆ coenzyme in the body. Pyridoxal phosphate (PLP) is the predominant biologically active form. Vitamin B₆ is not stable in heat or in alkaline conditions, so cooking and food processing reduce its content in food. Both coenzyme and free forms are absorbed in the small intestine and transported to the liver, where they are phosphorylated and released into circulation, bound to albumin for transport to tissues. Vitamin B₆ is stored in the muscle and only excreted in urine when intake is excessive.

PLP participates in amino acid synthesis and the interconversion of some amino acids. It catalyzes a step in the synthesis of hemoglobin, which is needed to transport oxygen in blood. PLP helps maintain blood glucose levels by facilitating the release of glucose from liver and muscle glycogen. It also plays a role in the synthesis of many neurotransmitters important for brain function. This has led some physicians to prescribe megadoses of B₆ to patients with psychological problems such as depression and mood swings, and to some women for premenstrual syndrome (PMS). It is unclear, however, whether this therapy is effective. PLP participates in the conversion of the amino acid tryptophan to niacin and helps avoid niacin deficiency. Pyridoxine affects immune function, as it is essential for the formation of a type of white blood cell.

Populations at risk of vitamin-B₆ deficiency include alcoholics and elderly persons who consume an inadequate diet. Individuals taking medication to treat Parkinson's disease or tuberculosis may take extra vitamin B₆ with physician supervision. Carpal tunnel syndrome, a nerve disorder of the wrist, has also been treated with large daily doses of B₆. However, data on its effectiveness are conflicting.

Folic Acid, Folate, Folacin (Vitamin B₉)

Folic Acid

Folacin or folate, as it is usually called, is the form of vitamin B₉ naturally present in foods, whereas folic acid is the synthetic form added to fortified foods and supplements. Both forms are absorbed in the small intestine and stored in the liver. The folic acid form, however, is more efficiently absorbed and available to the body. When consumed in excess of needs, both forms are excreted in urine and easily destroyed by heat, oxidation, and light.

Folic acid is a water soluble vitamin and is a member of the Vitamin B complex. Also known as Folacin, pteroyl-L-glutamic acid (PGA), vitamin Bc or vitamin M. Folic acid and its derivatives (mostly the tri and heptaglutamyl peptides) are widespread in nature. It is a specific growth factor for certain micro-organisms.  Found in yeast and liver in 1935.

All forms of this vitamin are readily converted to the coenzyme form called tetrahydrofolate (THFA), which plays a key role in transferring single-carbon methyl units during the synthesis of DNA and RNA, and in interconversions of amino acids. Folate also plays an important role in the synthesis of neurotransmitters. Meeting folate needs can improve mood and mental functions.

Function

• involved in the formation of new cells
• involved in the metabolism of ribonucleic acids (RNA) and deoxyribonucleic acids (DNA), essential for protein synthesis, formation of blood and transmission of genetic code
• essential during pregnancy to reduce the risk of neural tube defects (birth defects affecting the brain and/or spinal cord)essential for the normal growth and development of the fetus
• involved in the biosynthesis of purines, serines and glycine
• involved in some functions associated with Vitamin B12
• necessary for building resistance to diseases in the thymus gland of new born babies and infants
• may reduce the risk of cervical dysplasia
• necessary for red blood cell production

Food Source

• bananas
• Brewers's Yeast
• citrus fruits, peeled
• eggs
• fatty fish
• fresh nuts
• green leafy vegetables
• meats, especially pig liver and kidney
• milk
• oats
• pulses, such as lentils
• roasted nuts
• soy products, such as tofu
• unpolished brown rice
• wheat germ
• wheat bran
• wheat grains

Effective With

• B-Complex
• B12
• Biotin
• Pantothenic Acid
• Vitamin C

Increased Intakes Needed

• by alcohol drinkers
• by the elderly
• during pregnancy and breastfeeding
• if taking contraceptive pill
• if taking the drugs, Aspirin, Cholestyramine,  Isethionate, Isoniazid, Methotrexate,  Pentamidime, Phenytoin (may be neutralized), Primidone, Pyrimethamine, Triamterene,Trimethoprim

Used For

• malabsorption in geriatric patients
• megaloblastic anemia
• mental deterioration
• psychosis
• schizophrenia

Destroyed By

• leached into cooking water
• processing and cooking of vegetables, fruits and dairy products
• unstable to oxygen at high temperatures but protected by Vitamin C

Symptoms of Deficiency

• breathlessness
• fatigue
• irritability
• sleeplessness
• weakness

Deficiency Leads To

Various conditions relating to childbirth:

• abortion
• birth defects, such as neural tube defect which causes spina bifida
• hemorrhage following birth
• premature birth
• premature separation of the placenta from the uterus
• toxemia

As well as:

• megaloblastic anemia (red blood cells are large and uneven with a shortened life span)
• mild mental symptoms, such as forgetfulness and confusion

Symptoms of Toxicity

Folic Acid has a low toxicity but occasionally the following symptoms occur:

• abdominal distension
• flatulence (gas/wind)
• irritability
• loss of appetite
• nausea
• over-activity
• sleep disturbance
• symptoms of fever
• temperature rise

Long term high doses may cause Vitamin B12 losses from the body

Folate deficiency is one of the most common vitamin deficiencies. Early symptoms are nonspecific and include tiredness, irritability, and loss of appetite. Severe folate deficiency leads to macrocytic anemia, a condition in which cells in the bone marrow cannot divide normally and red blood cells remain in a large immature form called macrocytes. Large immature cells also appear along the length of the gastrointestinal tract, resulting in abdominal pain and diarrhea.

Pregnancy is a time of rapid cell multiplication and DNA synthesis, which increases the need for folate. Folate deficiency may lead to neural tube defects such as spina bifida (failure of the spine to close properly during the first month of pregnancy) and anencephaly (closure of the neural tube during fetal development, resulting in part of the cranium not being formed). Seventy percent of these defects could be avoided by adequate folate status before conception, and it is recommended that all women of childbearing age consume at least 400 micrograms (μg) of folic acid each day from fortified foods and supplements. Other groups at risk of deficiency include elderly persons and persons suffering from alcohol abuse or taking certain prescription drugs.

Vitamin B₁₂

Vitamin B₁₂ is found in its free-vitamin form, called cyanocobalamin, and in two active coenzyme forms. Absorption of vitamin B₁₂ requires the presence of intrinsic factor,

a protein synthesized by acid-producing cells of the stomach. The vitamin is absorbed in the terminal portion of the small intestine called the ileum. Most of body's supply of vitamin B₁₂ is stored in the liver.

Vitamin B12

Cyanocobalamin

Vitamin B₁₂ is defficiently conserved in the body, since most of it is secreted into bile and reabsorbed. This explains the slow development (about two years) of deficiency in people with reduced intake or absorption. Vitamin B₁₂ is stable when heated and slowly loses its activity when exposed to light, oxygen, and acid or alkaline environments.

Vitamin B₁₂ coenzymes help recycle folate coenzymes involved in the synthesis of DNA and RNA, and in the normal formation of red blood cells. Vitamin B₁₂ prevents degeneration of the myelin sheaths that cover nerves and help maintain normal electrical conductivity through the nerves.

Active center of tetrahydrofolate (THF). Note that the N⁵ position is the site of attachment of methyl groups, the N¹⁰ the site for attachment of formyl and formimino groups and that both N⁵ and N¹⁰ bridge the methylene and methenyl groups

Vitamin-B₁₂ deficiency results in pernicious anemia, which is caused by a genetic problem in the production of intrinsic factor. When this occurs, folate function is impaired, leading to macrocytic anemia due to interference in normal DNA synthesis. Unlike folate deficiency, the anemia caused by vitamin-B₁₂ deficiency is accompanied by symptoms of nerve degeneration, which if left untreated can result in paralysis and death.

Since vitamin B₁₂ is well conserved in the body, it is difficult to become deficient from dietary factors alone, unless a person is a strict vegan and consumes a

diet devoid of eggs and dairy for several years. Deficiency is usually observed when B₁₂ absorption is hampered by disease or surgery to the stomach or ileum, damage to gastric mucosa by alcoholism, or prolonged use of anti-ulcer medications that affect secretion of intrinsic factor. Agerelated decrease in stomach-acid production also reduces absorption of B₁₂ in elderly persons. These groups are advised to consume fortified foods or take a supplemental form of vitamin B₁₂.

Choline

For many years, choline was not considered a vitamin because the body makes enough of it to meet its needs in most age groups. However, research now shows that choline production in the body is not enough to cover requirements. Choline is not considered a B vitamin because it does not have a coenzyme function and the amount in the body is much greater than other B vitamins. Choline not only helps maintain the structural integrity of membranes surrounding every cell in the body, but also can play a role in nerve signaling, cholesterol transport, and energy metabolism. An "adequate intake" is 550 milligrams per day for men and 425 milligrams per day for women. Choline is widely found in foods, so it is unlikely that a dietary deficiency will occur.

Vitamin C (Ascorbic Acid)

Ascorbic Acid

In 1746, James Lind, a British physician, conducted the first nutrition experiment on human beings in an effort to find a cure for scurvy.

James Lind

James Lind (1716 – 1794),a British Royal Navy surgeon who, in 1774, identified that a quality in fruit prevented the disease of scurvy in what was the first recorded controlled experiment

However, it was not until nearly 200 years later that ascorbic acid, or vitamin C, was discovered. Vitamin C participates in many reactions by donating electrons as hydrogen atoms. In a reducing reaction, the electron in the hydrogen atom donated by vitamin C combines with other participating molecules, making vitamin C a reducing agent, essential to the activity of many enzymes. By neutralizing free radicals, vitamin C may reduce the risk of heart disease, certain forms of cancer, and cataracts.

Vitamin C is needed to form and maintain collagen, a fibrous protein that gives strength to connective tissues in skin, cartilage, bones, teeth, and joints. Collagen is also needed for the healing of wounds.

When added to meals, vitamin C increases intestinal absorption of iron from plant-based foods. High concentration of vitamin C in white blood cells enables the immune system to function properly by providing protection against oxidative damage from free radicals generated during their action against bacterial, viral, or fungal infections.

Vitamin C also recycles oxidized vitamin E for reuse in cells, and it helps folic acid convert to its active form, (THF). Vitamin C helps synthesize carnitine, adrenaline, epinephrine, the neurotransmitter serotonin, the thyroid hormone thyroxine, bile acids, and steroid hormones.

A deficiency of vitamin C causes widespread connective tissue changes throughout the body. Deficiencies may occur in people who eat few fruits and vegetables, follow restrictive diets, or abuse alcohol and drugs. Smokers also have lower vitamin-C status. Supplementation may be prescribed by physicians to speed the healing of bedsores, skin ulcers, fractures, burns, and after surgery. Research has shown that doses up to 1 gram per day may have small effects on duration and severity of the common cold, but not on the prevention of its occurrence.

Ascorbic acid

Ascorbic acid is required in the diet of only a few vertebrates — man, monkeys, the guinea pig, and certain fishes. Some insects and other invertebrates also require ascorbic acid, but most other higher animals and plants can synthesize ascorbic acid from glucose or other simple precursors. Ascorbic acid is not present in microorganisms, nor does it seem to be required.

Ascorbic acid is a strong reducing agent, readily losing hydrogen atoms to become dehydroascorbic acid, which also has vitamin C activity. However, vitamin activity is lost when the lactone ring of dehydroascorbic acid is hydrolyzed to yield diketogulonic acid.

Ascorbic Dehydroascorbic Diketogulonic

acid acid acid

Biological role of ascorbic acid:

- acts as a cofactor in the enzymatic hydroxylation of proline to hydroxyproline and in other hydroxylation reactions;

- inhibits the oxidation of hemoglobin;

- accelerates the oxidation of glucose in pentose phosphate pathway;

- reduces the disulfide bonds to sulfhydryl bonds;

- is necessary for hydroxylation of cholesterol;

- takes part in metabolism of adrenaline;

- is necessary for the metabolism of mineral elements (Fe, Ca);

- accelerates the synthesis of glycogen in liver.

While at sea in May 1747, Lind provided some crewmembers with two oranges

and one lemon per day, in addition to normal rations, while others continued on cider, vinegar or seawater, along with their normal rations. In the history of science this is considered to be the first example of a controlled experiment comparing results on two populations of a factor applied to one group only with all other factors the same.

In the hypovitaminosis of vitamin C the disease scurvy is developed. Main clinical symptoms of scurvy: delicacy, vertigo, palpitation, tachycardia, pain in the area of heart, dyspnea, petechias, odontorrhagia, dedentition.

Ascorbic acid and products of its decomposition are excreted from the organism via kidneys. In normal conditions 20-30 mg or 113,5-170,3 mkmol of ascorbic acid is excreted per day with urine.

In animal and plant tissues rather large concentrations of ascorbic acid are present, in comparison with other water-soluble vitamins; e.g., human blood plasma contains about 1 mg of ascorbic acid per 100 ml. Ascorbic acid is especially abundant in citrus fruits, tomatoes, currant, onion, garlic, cabbage, fruits of wild rose, needles of a pine-tree.

Sources of vitamin C

Vitamin C is obtained through the diet by the vast majority of the world's population. The richest natural sources are fruits and vegetables, and of those, the camu camu fruit and the billygoat plum contain the highest concentration of the vitamin. It is also present in some cuts of meat, especially liver. Vitamin C as ascorbic acid is the most widely taken nutritional supplement and is available in a variety of forms from tablets and drink mixes to pure ascorbic acid crystals in capsules or as plain powder.

Plant sources

Rose hips are a particularly rich source of vitamin C Citrus fruits (orange, lemon, grapefruit, lime), tomatoes, and potatoes are good common sources of vitamin C. Other foods that are good sources of vitamin C include papaya, broccoli, brussels sprouts, black currants, strawberries, cauliflower, spinach, cantaloupe, kiwifruit, cranberries and red peppers. Ascorbic acid in food is largely destroyed by cooking.

Although the symptoms of scurvy in man can be prevented by as little as 20 mg of ascorbic acid per day, there are evidences that far larger amounts may be required for completely normal physiological function and well-being. Day necessity of vitain C: 50 - 70 mg. But in different diseases, pregnancy, in hard physical and mental work, in growing organism, after operations the day requirement of vitamin C increased.

Vitamin P (bioflavonoids).

This is the group of compounds (rutin, hesperedin, katecholamines) supporting the elasticity of capillaries, strengthen their walls and decrease the permeability.

Vitamin P takes part in the oxidative-reduction processes. It oppresses the activity of enzyme hyaluronidase protecting the hyaluronic acid which is necessary for elasticity of vessel walls.

The deficiency of vitamin P in organism results in the petechias (dot hemorrhages on skin).

Day necessity of vitamin P is not clear exactly (about 25-50 mg). In some diseases 1-2 g per day of vitamin P is administrated.