Vitamin C or L-ascorbic acid, or simply ascorbate (the anion of ascorbic acid), is an essential nutrient for humans and certain other animal species. Vitamin C refers to a number of vitamers that have vitamin C activity in animals, including ascorbic acid and its salts, and some oxidized forms of the molecule like dehydroascorbic acid. Ascorbate and ascorbic acid are both naturally present in the body when either of these is introduced into cells, since the forms interconvert according to pH. Vitamin C is a cofactor in at least eight enzymatic reactions, including several collagen synthesis reactions that, when dysfunctional, cause the most severe symptoms of scurvy. In animals, these reactions are especially important in wound-healing and in preventing bleeding from capillaries. Ascorbate may also act as an antioxidant against oxidative stress. However, the fact that the enantiomer D-ascorbate (not found in nature) has identical antioxidant activity to L-ascorbate, yet far less vitamin activity, underscores the fact that most of the function of L-ascorbate as a vitamin relies not on its antioxidant properties, but upon enzymic reactions that are stereospecific. “Ascorbate” without the letter for the enantiomeric form is always presumed to be the chemical L-ascorbate. In humans, vitamin C is essential to a healthy diet as well as being a highly effective antioxidant, acting to lessen oxidative stress; a substrate for ascorbate peroxidase in plants (APX is plant specific enzyme); and an enzyme cofactor for the biosynthesis of many important biochemicals. Vitamin C acts as an electron donor for important enzymes. The North American Dietary Reference Intake recommends 90 milligrams per day and no more than 2 grams (2,000 milligrams) per day. Other related species sharing the same inability to produce vitamin C require exogenous vitamin C consumption 20 to 80 times this reference intake. There is continuing debate within the scientific community over the best dose schedule (the amount and frequency of intake) of vitamin C for maintaining optimal health in humans. A balanced diet without supplementation usually contains enough vitamin C to prevent scurvy in an average healthy adult, while those who are pregnant, smoke tobacco, or are under stress require slightly more.
Vitamin B complex
Thiamine or thiamin or vitamin B1, named as the “thio-vitamine” (“sulfur-containing vitamin”) is a water-soluble vitamin of the B complex. All living organisms use thiamine, but it is synthesized only in bacteria, fungi, and plants. Animals must obtain it from their diet, and thus, for them, it is an essential nutrient. In mammals, deficiency results in Korsakoff’s syndrome, optic neuropathy, and a disease called beriberi that affects the peripheral nervous system (polyneuritis) and/or the cardiovascular system. Thiamine deficiency has a potentially fatal outcome if it remains untreated. In less severe cases, nonspecific signs include malaise, weight loss, irritability and confusion. The stable and non-hygroscopic salt thiamine mononitrate is the vitamer used for flour and food fortification. Thiamine is on the World Health Organization’s List of Essential Medicines, a list of the most important medication needed in a basic health system. n general, cereal grains are the most important dietary sources of thiamine, by virtue of their ubiquity. Of these, whole grains contain more thiamine than refined grains, as thiamine is found mostly in the outer layers of the grain and in the germ (which are removed during the refining process). For example, 100 g of whole-wheat flour contains 0.55 mg of thiamine, while 100 g of white flour contains only 0.06 mg of thiamine. In the US, processed flour must be enriched with thiamine mononitrate (along with niacin, ferrous iron, riboflavin, and folic acid) to replace that lost in processing. In Australia, thiamine, folic acid, and iodised salt are added for the same reason. The RDA in most countries is set at about 1.4 mg. However, tests on female volunteers at daily doses of about 50 mg have claimed an increase in mental acuity. There are no reports available of adverse effects from consumption of excess thiamine by ingestion of food and supplements. Because the data is inadequate for a quantitative risk assessment, no Tolerable Upper Intake Level (UL) can be derived for thiamine. Thiamine derivatives and thiamine-dependent enzymes are present in all cells of the body, thus a thiamine deficiency would seem to adversely affect all of the organ systems. However, the nervous system is particularly sensitive to thiamine deficiency, because of its dependence on oxidative metabolism.
Riboflavin (vitamin B2) is part of the vitamin B group. It is central component of the cofactors FAD and FMN and as such required for a variety of flavoprotein enzyme reactions including activation of other vitamins. It was formerly known as vitamin G. Sources of riboflavin are milk, cheese, leaf vegetables, liver, kidneys, legumes, yeast, mushrooms, and almonds.Yeast extract is considered to be exceptionally rich in vitamin B2. Cereals contain relatively low concentrations of flavins, but are important sources in those parts of the world where cereals constitute the staple diet. It is used in baby foods, breakfast cereals, pastas, sauces, processed cheese, fruit drinks, vitamin-enriched milk products, and some energy drinks. It is difficult to incorporate riboflavin into many liquid products because it has poor solubility in water, hence the requirement for riboflavin-5′-phosphate (E101a), a more soluble form of riboflavin. Riboflavin is also used as a food coloring and as such is designated in Europe as the E number E101. Riboflavin is generally stable during the heat processing and normal cooking of foods if light is excluded. The alkaline conditions in which riboflavin is unstable are rarely encountered in foodstuffs. Riboflavin degradation in milk can occur slowly in dark during storage in the refrigerator. The current RDAs for riboflavin for adult men and women are 1.3 mg/day and 1.1 mg/day, respectively; the estimated average requirement for adult men and women are 1.1 mg and 0.9 mg, respectively. Recommendations for daily riboflavin intake increase with pregnancy and lactation to 1.4 mg and 1.6 mg, respectively (1in advanced). For infants, the RDA is 0.3-0.4 mg/day and for children it is 0.6-0.9 mg/day.
Niacin (also known as vitamin B3 or nicotinic acid) is an organic compound and depending on the definition used, one of the 20 to 80 essential human nutrients. Insufficient niacin in the diet can cause nausea, skin and mouth lesions, anemia, headaches, and tiredness. Chronic niacin deficiency leads to a disease called pellagra. The lack of niacin may also be observed in pandemic deficiency disease, which is caused by a lack of five crucial vitamins (niacin, vitamin C, thiamin, vitamin D, and vitamin A) and is usually found in areas of widespread poverty and malnutrition. Niacin has not been found to be useful in decreasing the risk of cardiovascular disease in those already on a statin but appears to be effective in those not taking a statin. One recommended daily allowance of niacin is 2–12 mg/day for children, 14 mg/day for women, 16 mg/day for men, and 18 mg/day for pregnant or breast-feeding women. Tolerable upper intake levels (UL) for adult men and women is considered to be 35 mg/day by the Dietary Reference Intake system to avoid flushing. In general, niacin status is tested through urinary biomarkers,which are believed to be more reliable than plasma levels.
Pantothenic acid, also called pantothenate or vitamin B5 (a B vitamin), is a water-soluble vitamin. For many animals, pantothenic acid is an essential nutrient. Animals require pantothenic acid to synthesize coenzyme-A (CoA), as well as to synthesize and metabolize proteins, carbohydrates, and fats. It is commonly found as its alcohol analog, the provitamin panthenol (pantothenol), and as calcium pantothenate. Pantothenic acid is an ingredient in some hair and skin care products. Pantothenic acid is used in the synthesis of coenzyme A (CoA). CoA is important in energy metabolism for pyruvate to enter the tricarboxylic acid cycle (TCA cycle) as acetyl-CoA, and for α-ketoglutarate to be transformed to succinyl-CoA in the cycle. CoA is also important in the biosynthesis of many important compounds such as fatty acids, cholesterol, and acetylcholine. CoA is incidentally also required in the formation of ACP, which is also required for fatty acid synthesis in addition to CoA. Small quantities of pantothenic acid are found in most foods. The major food source of pantothenic acid is meat. The concentration found in animal muscle is about half that in human muscle. Whole grains are another good source of the vitamin, but milling removes much of the pantothenic acid, as it is found in the outer layers of whole grains. Vegetables, such as avocados and broccoli, also have an abundance. In animal feeds, the most important sources are alfalfa, cereal, condensed fish solutions, peanut meal, molasses, mushrooms, rice, wheat bran, and yeasts. The most significant sources of pantothenic acid in nature are coldwater fish ovaries and royal jelly. The derivative of pantothenic acid, pantothenol (panthenol), is a more stable form of the vitamin and is often used as a source of the vitamin in multivitamin supplements. Another common supplemental form of the vitamin is calcium pantothenate. Calcium pantothenate is often used in dietary supplements because, as a salt, it is more stable than pantothenic acid in the digestive mentation may improve oxygen utilization efficiency and reduce lactic acid accumulation in athletes. Pantothenate in the form of 4’phosphopantetheine is considered to be the more active form of the vitamin in the body; however, any derivative must be broken down to pantothenic acid before absorption. 10 mg of calcium pantothenate is equivalent to 9.2 mg of pantothenic acid.
Vitamin B6 refers to a group of chemically very similar compounds which can be interconverted in biological systems. Vitamin B6 is part of the vitamin B complex group, and its active form, Pyridoxal 5′-phosphate (PLP) serves as a cofactor in many enzyme reactions in amino acid, glucose, and lipid metabolism. PLP, the metabolically active form of vitamin B6, is involved in many aspects of macronutrient metabolism, neurotransmitter synthesis, histamine synthesis, hemoglobin synthesis and function, and gene expression. PLP generally serves as a coenzyme (cofactor) for many reactions including decarboxylation, transamination, racemization, elimination, replacement, and beta-group interconversion. The liver is the site for vitamin B6 metabolism.
Biotin, also known as vitamin H or coenzyme R, is a water-soluble B-vitamin. Biotin is necessary for cell growth, the production of fatty acids, and the metabolism of fats and amino acids. Biotin assists in various metabolic reactions involving the transfer of carbon dioxide. It may also be helpful in maintaining a steady blood sugar level. Biotin is often recommended as a dietary supplement for strengthening hair and nails, though scientific data supporting this outcome are weak. Nevertheless, biotin is found in many cosmetics and health products for the hair and skin.
Folic acid is a B vitamin. Vitamin B9 is essential for numerous bodily functions. Humans cannot synthesize folates de novo; therefore, folate (folic acid) has to be supplied through the diet to meet their daily requirements. The human body needs folate to synthesize DNA, repair DNA, and methylate DNA as well as to act as a cofactor in certain biological reactions. It is especially important in aiding rapid cell division and growth, such as in infancy and pregnancy. Children and adults both require folate to produce healthy red blood cells and prevent anemia. A lack of dietary folates can lead to folate deficiency. A complete lack of dietary folate takes months before deficiency develops as normal individuals have about 500–20,000 µg of folate in body stores. This deficiency can result in many health problems, the most notable one being neural tube defects in developing embryos. Common symptoms of folate deficiency include diarrhea, macrocytic anemia with weakness or shortness of breath, nerve damage with weakness and limb numbness (peripheral neuropathy), pregnancy complications, mental confusion, forgetfulness or other cognitive deficits, mental depression, sore or swollen tongue, peptic or mouth ulcers, headaches, heart palpitations, irritability, and behavioral disorders.
Vitamin B12 also called cobalamin, is a water-soluble vitamin with a key role in the normal functioning of the brain and nervous system, and for the formation of blood. It is one of the eight B vitamins. It is normally involved in the metabolism of every cell of the human body, especially affecting DNA synthesis and regulation, but also fatty acid metabolism and amino acid metabolism. Neither fungi, plants, nor animals are capable of producing vitamin B12. Only bacteria and archaea have the enzymes required for its synthesis, although many foods are a natural source of B12 because of bacterial symbiosis. The vitamin is the largest and most structurally complicated vitamin and can be produced industrially only through bacterial fermentation-synthesis. The dietary reference intake for an adult ranges from 2 to 3 µg per day (US), and 1.5 µg per day (UK). But according to a new study, the DRI should be 4 to 7 µg per day. The Center for Food Safety and Applied Nutrition recommends 6 µg per day, based on a caloric intake of 2,000 calories, for adults and children four or more years of age. Vitamin B12 is believed to be safe when used orally in amounts that do not exceed the recommended dietary allowance (RDA). There have been studies that showed no adverse consequences of doses above the RDA. The RDA for vitamin B12 in pregnant women is 2.6 µg per day and 2.8 µg during lactation periods. There is insufficient reliable information available about the safety of consuming greater amounts of vitamin B12 during pregnancy.