Niacin (also known as vitamin B₃, nicotinic acid and vitamin PP) is an organic compound An organic compound is any member of a large class of chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of compounds such as carbonates, simple oxides of carbon and cyanides, as well as the allotropes of carbon, are considered inorganic. The distinction between "organic" and " with the formula A chemical formula or molecular formula is a way of expressing information about the atoms that constitute a particular chemical compound C₅H₄NCO₂H and, depending on the definition used, one of the between forty to eighty essential human nutrients An essential nutrient is a nutrient required for normal body functioning that either cannot be synthesized by the body at all, or cannot be synthesized in amounts adequate for good health , and thus must be obtained from a dietary source. Essential nutrients are also defined by the collective physiological evidence for their importance in the diet,. This colourless, water-soluble solid is a derivative of pyridine Pyridine is a heterocyclic organic compound with the chemical formula C5 , with a carboxyl group Carboxylic acids are organic acids characterized by the presence of at least one carboxyl group. The general formula of a carboxylic acid is R-COOH, where R is some monovalent functional group (COOH) at the 3-position. Other forms of vitamin B₃ include the corresponding amide In chemistry, an amide is usually an organic compound that contains the functional group consisting of an acyl group linked to a nitrogen atom (N). The term refers both to a class of compounds and a functional group within those compounds. The term amide also refers to deprotonated form of ammonia (NH3) or an amine, often represented as anions R2N-, nicotinamide Nicotinamide, also known as niacinamide and nicotinic acid amide, is the amide of nicotinic acid . Nicotinamide is a water-soluble vitamin and is part of the vitamin B group. Nicotinic acid, also known as niacin, is converted to nicotinamide in vivo, and, though the two are identical in their vitamin functions, nicotinamide does not have the same ("niacinamide"), where the carboxyl group has been replaced by a carboxamide group (CONH₂), as well as more complex amides and a variety of esters. The terms niacin, nicotinamide, and vitamin B₃ are often used interchangeably to refer to any member of this family of compounds, since they have the same biochemical activity.

Niacin is converted to nicotinamide and then to NAD Nicotinamide adenine dinucleotide, abbreviated NAD+, is a coenzyme found in all living cells. The compound is a dinucleotide, since it consists of two nucleotides joined through their phosphate groups, with one nucleotide containing an adenine base and the other containing nicotinamide and NADP Nicotinamide adenine dinucleotide phosphate is used in anabolic reactions, such as lipid and nucleic acid synthesis, which require NADPH as a reducing agent in vivo In vivo is experimentation using a whole, living organism as opposed to a partial or dead organism, or an in vitro controlled environment. Animal testing and clinical trials are two forms of in vivo research. In vivo testing is often employed over in vitro because it is better suited for observing the overall effects of an experiment on a living. Although the two are identical in their vitamin activity, nicotinamide does not have the same pharmacological effects as niacin, which occur as side effects of niacin's conversion. Nicotinamide does not reduce cholesterol or cause flushing For a person to flush is to become markedly red in the face and often other areas of the skin, from various physiological conditions. Flushing is generally distinguished, despite a close physiological relation between them, from blushing, which is milder, generally restricted to the face, cheeks or ears, and generally assumed to reflect.^[1] Nicotinamide may be toxic to the liver at doses exceeding 3 g/day for adults.^[2] Niacin is a precursor to NAD+/NADH Nicotinamide adenine dinucleotide, abbreviated NAD+, is a coenzyme found in all living cells. The compound is a dinucleotide, since it consists of two nucleotides joined through their phosphate groups, with one nucleotide containing an adenine base and the other containing nicotinamide and NADP+/NADPH Nicotinamide adenine dinucleotide phosphate is used in anabolic reactions, such as lipid and nucleic acid synthesis, which require NADPH as a reducing agent, which play essential metabolic Metabolism is the set of chemical reactions that happen in living organisms to maintain life. These processes allow organisms to grow and reproduce, maintain their structures, and respond to their environments. Metabolism is usually divided into two categories. Catabolism breaks down organic matter, for example to harvest energy in cellular roles in living cells The cell is the functional basic unit of life. It was discovered by Robert Hooke and is the functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. Some organisms, such as most bacteria, are unicellular . Other organisms, such as humans,.^[3] Niacin is involved in both DNA repair, and the production of steroid hormones Steroid hormones are steroids that act as hormones. Steroid hormones can be grouped into five groups by the receptors to which they bind: glucocorticoids, mineralocorticoids, androgens, estrogens, and progestagens. Vitamin D derivatives are a sixth closely related hormone system with homologous receptors, though technically sterols rather than in the adrenal gland In mammals, the adrenal glands are the triangular-shaped endocrine glands that sit on top of the kidneys. They are chiefly responsible for releasing hormones in conjunction with stress through the synthesis of corticosteroids and catecholamines, including cortisol and adrenaline (epinephrine), respectively.

Niacin is one of five vitamins associated with a pandemic A pandemic is an epidemic of infectious disease that is spreading through human populations across a large region; for instance a continent, or even worldwide. A widespread endemic disease that is stable in terms of how many people are getting sick from it is not a pandemic. Further, flu pandemics exclude seasonal flu, unless the flu of the season deficiency disease Deficiency diseases are diseases in humans that are directly or indirectly caused by a lack of essential nutrients in the diet. Deficiency diseases are commonly associated with chronic malnutrition. Additionally, conditions such as obesity from overeating can also cause, or contribute to, serious health problems. Excessive intake of some nutrients:

• niacin deficiency (pellagra Pellagra is a vitamin deficiency disease most commonly caused by a chronic lack of niacin in the diet. It can be caused by decreased intake of niacin or tryptophan, and possibly by excessive intake of leucine. It may also result from alterations in protein metabolism in disorders such as carcinoid syndrome. A deficiency of the amino acid lysine)
• vitamin C Vitamin C or L-ascorbic acid or L-ascorbate is an essential nutrient for humans and certain other animal species, in which it functions as a vitamin. In living organisms, ascorbate is an anti-oxidant, since it protects the body against oxidative stress. It is also a cofactor in at least eight enzymatic reactions, including several collagen deficiency (scurvy Scurvy is a disease resulting from a deficiency of vitamin C, which is required for the synthesis of collagen in humans. The chemical name for vitamin C, ascorbic acid, is derived from the Latin name of scurvy, scorbutus, which also provides the adjective scorbutic . Scurvy leads to the formation of spots on the skin, spongy gums, and bleeding)
• thiamin Thiamine or thiamin or vitamin B1 , and named as the "thio-vitamine" ("sulfur-containing vitamin") is a water-soluble vitamin of the B complex. First named aneurin for the detrimental neurological effects of its lack in the diet, it was eventually assigned the generic descriptor name vitamin B1. Its phosphate derivatives are deficiency (beriberi Beriberi is a nervous system ailment caused by a thiamine deficiency (deficiency of vitamin B1) in the diet. Thiamine is involved in the breakdown of energy molecules such as glucose and is also found on the membranes of neurons. Symptoms of beriberi include severe lethargy and fatigue, together with complications affecting the cardiovascular,)
• vitamin D Vitamin D is a group of fat-soluble secosteroids, the two major physiologically relevant forms of which are vitamin D2 and vitamin D3 (cholecalciferol). Vitamin D without a subscript refers to either D2 or D3 or both. Vitamin D3 is produced in the skin of vertebrates after exposure to ultraviolet B light from the sun or artificial sources, and deficiency (rickets Rickets is a softening of bones in children potentially leading to fractures and deformity. Rickets is among the most frequent childhood diseases in many developing countries. The predominant cause is a vitamin D deficiency, but lack of adequate calcium in the diet may also lead to rickets . Although it can occur in adults, the majority of cases)
• vitamin A deficiency Vitamin A deficiency is a lack of vitamin A in humans. It is common in developing countries but rarely seen in developed countries. Night blindness is one of the first signs of vitamin A deficiency. Complete blindness can also occur due to retinal injury - Vitamin A has a major role in phototransduction. Approximately 250,000 to 500,000.

In larger doses, niacin can reverse atherosclerosis Atherosclerosis is a condition in which an artery wall thickens as the result of a build-up of fatty materials such as cholesterol. It is a syndrome affecting arterial blood vessels, a chronic inflammatory response in the walls of arteries, in large part due to the accumulation of macrophage white blood cells and promoted by low-density by lowering low-density lipoprotein LDL-density lipoprotein is one of the five major groups of lipoproteins (chylomicrons, VLDL, IDL, HDL, LDL) that enable lipids like cholesterol and triglycerides to be transported within the water-based bloodstream. Medically, estimates of cholesterol content carried by LDL particles are used as part of a cholesterol blood test; direct LDL (LDL) and favorably affecting other compounds.^[4]

History

Niacin was first described by Hugo Weidel Hugo Weidel 13 November 1849 – 7 June 1899) was a Austrian chemist. Famous for inventing Weidel's reaction and describing the structure of niacin. Received Lieben Prize in 1880 in 1873 in his studies of nicotine Nicotine is an alkaloid found in the nightshade family of plants that constitutes approximately 0.6–3.0% of dry weight of tobacco, with biosynthesis taking place in the roots and accumulation occurring in the leaves. It functions as an antiherbivore chemical with particular specificity to insects; therefore nicotine was widely used as an.^[5] The original preparation remains useful: The oxidation of nicotine Nicotine is an alkaloid found in the nightshade family of plants that constitutes approximately 0.6–3.0% of dry weight of tobacco, with biosynthesis taking place in the roots and accumulation occurring in the leaves. It functions as an antiherbivore chemical with particular specificity to insects; therefore nicotine was widely used as an using nitric acid Colorless when pure, older samples tend to acquire a yellow cast due to the accumulation of oxides of nitrogen. If the solution contains more than 86% nitric acid, it is referred to as fuming nitric acid. Fuming nitric acid is characterized as white fuming nitric acid and red fuming nitric acid, depending on the amount of nitrogen dioxide present.^[6] Niacin was extracted from livers by Conrad Elvehjem who later identified the active ingredient, then referred to as the "pellagra-preventing factor" and the "anti-blacktongue factor."^[7] When the biological significance of nicotinic acid was realized, it was thought appropriate to choose a name to dissociate it from nicotine, to avoid the perception that vitamins or niacin-rich food contains nicotine, or that cigarettes contain vitamins. The resulting name 'niacin' was derived from nicotinic acid + vitamin.

Carpenter found in 1951 that niacin in corn is biologically unavailable, and can be released only in very alkaline lime water of pH In chemistry, pH is a measure of the acidity or basicity of a solution. It approximates but is not equal to p[H], the negative logarithm of the molar concentration of dissolved hydronium ions (H3O+); a low pH indicates a high concentration of hydronium ions, while a high pH indicates a low concentration. Crudely, this negative of the logarithm 11.^[8] This process is known as nixtamalization Nixtamalization typically refers to a process for the preparation of maize , or other grain, in which the grain is soaked and cooked in an alkaline solution, usually limewater, and hulled. The term can also refer to the removal via an alkali process of the pericarp from other grains such as sorghum. Maize subjected to the nixtamalization process.^[9]

Niacin is referred to as vitamin B₃ because it was the third of the B vitamins The B vitamins are eight water-soluble vitamins that play important roles in cell metabolism. The B vitamins were once thought to be a single vitamin, referred to as vitamin B . Later research showed that they are chemically distinct vitamins that often coexist in the same foods. In general, supplements containing all eight are referred to as a to be discovered. It has historically been referred to as "vitamin PP" or "vitamin P-P".

Dietary needs

The 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.^[10] The upper limit for adult men and women is 35 mg/day, which is based on flushing as the critical adverse effect.

In general, niacin status is tested through urinary biomarkers A biomarker, or biological marker, is in general a substance used as an indicator of a biological state. It is a characteristic that is objectively measured and evaluated as an indicator of normal biological processes, pathogenic processes, or pharmacologic responses to a therapeutic intervention. It is used in many scientific fields,^[11] which are believed to be more reliable than plasma levels.^[12]

Deficiency

At the present time, niacin deficiency is rarely seen in developed countries but it is usually apparent in conditions of poverty, malnutrition, and chronic alcoholism^[13]. It also tends to occur in areas where people eat maize Maize , known in many English-speaking countries as corn, is a grass domesticated by indigenous peoples in Mesoamerica in prehistoric times. The Aztecs and Mayans cultivated it in numerous varieties throughout central and southern Mexico, to cook or grind in a process called nixtamalization. Later the crop spread through much of the Americas (corn, the only grain low in niacin) as a staple food. A special cooking technique called nixtamalization Nixtamalization typically refers to a process for the preparation of maize , or other grain, in which the grain is soaked and cooked in an alkaline solution, usually limewater, and hulled. The term can also refer to the removal via an alkali process of the pericarp from other grains such as sorghum. Maize subjected to the nixtamalization process is needed to increase the bioavailability of niacin during maize meal/flour production.

Mild niacin deficiency has been shown to slow metabolism, causing decreased tolerance to the cold.

Severe deficiency of niacin in the diet causes the disease pellagra Pellagra is a vitamin deficiency disease most commonly caused by a chronic lack of niacin in the diet. It can be caused by decreased intake of niacin or tryptophan, and possibly by excessive intake of leucine. It may also result from alterations in protein metabolism in disorders such as carcinoid syndrome. A deficiency of the amino acid lysine which is characterized by diarrhea, dermatitis, and dementia as well as “necklace” lesions on the lower neck, hyperpigmentation, thickening of the skin, inflammation of the mouth and tongue, digestive disturbances, amnesia, delirium, and eventually death, if left untreated^[14]. Common psychiatric symptoms of niacin deficiency include irritability, poor concentration, anxiety, fatigue, restlessness, apathy, and depression^[14]. Studies have indicated that, in patients with alcoholic pellagra, niacin deficiency may be an important factor influencing both the onset and severity of this condition. Alcoholic patients typically experience increased intestinal permeability leading to negative health outcomes .

Hartnup’s disease is a hereditary Heredity is the passing of traits to offspring . This is the process by which an offspring cell or organism acquires or becomes predisposed to the characteristics of its parent cell or organism. Through heredity, variations exhibited by individuals can accumulate and cause a species to evolve. The study of heredity in biology is called genetics, nutritional disorder resulting in niacin deficiency^[14]. This condition was first identified in the 1950s by the Hartnup family in London. It is due to a deficit in the intestines and kidneys, making it difficult for the body to break down and absorb dietary tryptophan. The resulting condition is similar to pellagra, including symptoms of red, scaly rash, and sensitivity to sunlight. Oral niacin is given as a treatment for this condition in doses ranging from 40–200 mg, with a good prognosis if identified and treated early^[14]. Niacin synthesis is also deficient in carcinoid syndrome Carcinoid syndrome refers to the array of symptoms that occur secondary to carcinoid tumors, because of metabolic diversion of its precursor tryptophan Tryptophan is one of the 20 standard amino acids, as well as an essential amino acid in the human diet. It is encoded in the standard genetic code as the codon UGG. Only the L-stereoisomer of tryptophan is used in structural or enzyme proteins, but the D-stereoisomer is occasionally found in naturally produced peptides (for example, the marine to form serotonin Serotonin or 5-Hydroxytryptamine (5-HT) is a monoamine neurotransmitter, biochemically derived from tryptophan, that is primarily found in the gastrointestinal (GI) tract, platelets, and central nervous system (CNS) of humans and animals. It is a well-known contributor to feelings of well-being.

Lipid-modifying effects

In pharmacological doses, niacin has been proven to reverse atherosclerosis by reducing total cholesterol, triglyceride, very-low-density lipoprotein (VLDL), and low-density lipoprotein (LDL); and increasing high-density lipoprotein (HDL). It has been proposed that niacin has the ability to lower lipoprotein(a) Lipoprotein (also called Lp(a)) is a lipoprotein subclass. Studies have identified Lp(a) as a putative risk factor for atherosclerotic diseases such as coronary heart disease and stroke, which is beneficial at reducing thrombotic tendency.^[15]

Niacin, prescribed in doses between 1000 and 2000 mg two to three times daily,^[16] blocks the breakdown of fats Fats consist of a wide group of compounds that are generally soluble in organic solvents and largely insoluble in water. Chemically, fats are generally triesters of glycerol and fatty acids. Fats may be either solid or liquid at room temperature, depending on their structure and composition. Although the words "oils", "fats", in adipose tissue In histology, adipose tissue or body fat or just fat is loose connective tissue composed of adipocytes. It is technically composed of roughly only 80% fat; fat in its solitary state exists in the liver and muscles. Adipose tissue is derived from lipoblasts. Its main role is to store energy in the form of fat, although it also cushions and, more specifically the very-low-density lipoprotein Very-low-density lipoprotein is a type of lipoprotein made by the liver. VLDL is one of the five major groups of lipoproteins (chylomicrons, VLDL, intermediate-density lipoprotein, low-density lipoprotein, high-density lipoprotein) that enable fats and cholesterol to move within the water-based solution of the bloodstream. VLDL is assembled in the (VLDL), precursor of low-density lipoprotein LDL-density lipoprotein is one of the five major groups of lipoproteins (chylomicrons, VLDL, IDL, HDL, LDL) that enable lipids like cholesterol and triglycerides to be transported within the water-based bloodstream. Medically, estimates of cholesterol content carried by LDL particles are used as part of a cholesterol blood test; direct LDL (LDL) or "bad" cholesterol. Because niacin blocks breakdown of fats, it causes a decrease in free fatty acids in the blood and, as a consequence, decreased secretion of VLDL and cholesterol by the liver.^[17]

By lowering VLDL levels, niacin also increases the level of high-density lipoprotein (HDL) or "good" cholesterol in blood, and therefore it is sometimes prescribed for patients with low HDL, who are also at high risk of a heart attack.^[18][19]

The ARBITER 6-HALTS study, reported at the 2009 annual meeting of the American Heart Association and in the New England Journal of Medicine^[20] concluded that, when added to statins, 2000 mg/day slow-release niacin was more effective than ezetimibe (Zetia) in reducing carotid intima-media thickness, a marker of atherosclerosis.^[21]

As of August 2008^[update], a combination of niacin with laropiprant is tested in a clinical trial. Laropiprant reduces facial flushes induced by niacin. ^[22]

Toxicity

Pharmacological doses of niacin (1.5 - 6 g per day) often lead to side effects that can include dermatological conditions such as skin flushing and itching, dry skin, skin rashes including acanthosis nigricans. Gastrointestinal complaints, such as dyspepsia (indigestion) and liver toxicity [fulminant hepatic failure], have also been reported. Side effects of hyperglycemia, cardiac arrhythmias and "birth defects in experimental animals" have also been reported.^[23] The flush lasts for about 15 to 30 minutes, and is sometimes accompanied by a prickly or itching sensation, in particular, in areas covered by clothing. This effect is mediated by prostaglandin and can be blocked by taking 300 mg of aspirin half an hour before taking niacin, or by taking one tablet of ibuprofen per day. Taking the niacin with meals also helps reduce this side effect. After several weeks of a consistent dose, most patients no longer flush.^[24] Slow- or "sustained"-release forms of niacin have been developed to lessen these side effects.^[17][25] One study showed the incidence of flushing was significantly lower with a sustained release formulation^[26] though doses above 2 g per day have been associated with liver damage, in particular, with slow-release formulations.^[23] Flushing is often thought to involve histamine, but histamine has been shown not to be involved in the reaction.^[27] Prostaglandin (PGD₂) is the primary cause of the flushing reaction, with serotonin appearing to have a secondary role in this reaction.^[27]

High-dose niacin may also elevate blood sugar, thereby worsening diabetes mellitus.^[23]

Hyperuricemia is another side effect of taking high-dose niacin, and may exacerbate gout.^[28]

Niacin at doses used in lowering cholesterol has been associated with birth defects in laboratory animals, with possible consequences for infant development in pregnant women.^[23]

Niacin at extremely high doses can have life-threatening acute toxic reactions.^[29] Extremely high doses of niacin can also cause niacin maculopathy, a thickening of the macula and retina, which leads to blurred vision and blindness. This maculopathy is reversible after stopping niacin intake.^[30]

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