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niacin

  ('ə-sĭn) pronunciation
n.

A white crystalline acid, C5H4NCOOH, that is a component of the vitamin B complex found in meat, wheat germ, dairy products, and yeast and is used to treat and prevent pellagra. Also called nicotinic acid.

[NI(COTINIC) AC(ID) + –IN.]


 
 

A vitamin also known as nicotinic acid, a component of the vitamin B complex. It is a white water-soluble powder stable to heat, acid, and alkali, with the structure shown below.

Many animals, including humans, are capable of synthesizing niacin in varying degrees from the amino acid tryptophan. Niacin is widely distributed in foods. Yeasts, wheat germ, and meats, particularly organ meats, are rich sources of the vitamin. Some foods such as milk are relatively poor sources of niacin but contain generous quantities of tryptophan.

Niacin-deficiency disease is known as pellagra and is particularly prevalent among the poor people whose diet is largely corn. The recommended dietary allowance for niacin is 6.6 niacin equivalents per 1000 kcal. See also Vitamin.


 

A vitamin; one of the B complex without a numerical designation. It is sometimes (incorrectly) referred to as vitamin B3, and formerly vitamin PP (pellagra preventative). Deficiency leads to pellagra, which is fatal if untreated. Niacin is the generic descriptor for two compounds that have the biological activity of the vitamin: nicotinic acid and its amide, nicotinamide. In USA niacin is used specifically to mean nicotinic acid, and niacinamide for nicotinamide.

The metabolic function of niacin is in the coenzymes NAD (nicotinamide adenine dinucleotide) and NADP (nicotinamide adenine dinucleotide phosphate), which act as intermediate hydrogen carriers in a wide variety of oxidation and reduction reactions.

Niacin can also be formed in the body from the amino acid tryptophan; on average 60 mg of dietary tryptophan is equivalent to 1 mg of preformed niacin. The total niacin content of foods is generally expressed as mg niacin equivalents; the sum of preformed niacin plus one-sixtieth of the tryptophan. This means that most foods that are good sources of protein are also good sources of niacin. In cereals niacin is largely present as niacytin, which is not biologically available; therefore the preformed niacin content of cereals is generally ignored when calculating intakes. Free niacin is added to white flour and enriched breakfast cereals in many countries.

 

nicotinamide; nicotinic acid; vitamin B3

A water-soluble nutrient belonging to the vitamin B complex. Like other B vitamins, niacin plays an important role in carbohydrate metabolism. It is also indispensable for fat and protein metabolism, and inhibits cholesterol synthesis.

The link between niacin (specifically nicotinic acid) and cholesterol reduction was first made by Dr R. Altschul in 1955, but it was brought to public attention in 1990 by Robert Kowalski in his book entitled The 8-week cholesterol cure. As a result, some people have taken excessive amounts of niacin in the belief that it will protect against high blood cholesterol levels. This practice is potentially dangerous. High doses (greater than 500 mg per day), or slow-release preparations of niacin which elevate blood concentrations for a long time, can lead to irreversible liver damage. Large doses of niacin can also decrease fat mobilization and the ability to do physical work.

Although the precise amount varies depending on energy expenditure, approximately 20 milligrams of niacin are needed per day. The body stores very little. It can synthesize niacin from the amino acid tryptophan. This synthesis may be enough to meet the daily requirement, but niacin can also be obtained from foods such as meat, fish, brown rice, beans, and yeast extract (the richest source, with as much as 67 mg per 100 g). Deficiency can result in a disease called pellagra, early symptoms of which include muscular weakness, general fatigue, loss of appetite, indigestion, and minor skin complaints. Pellagra is unlikely to occur in individuals who eat a balanced diet.

 

n
vitamin B3

trade name: generic niacin (nicotinic acid); drug class: vitamin B3; action: needed for conversion of fats, protein, carbohydrates by oxidation-reduction; acts directly on vascular smooth muscle, causing vasodilation; uses: pellagra, hyperlipidemias, peripheral vascular disease.

 

Description

Niacin, also known as Vitamin B3, is important for the normal function of many bodily processes. Like other B vitamins, it is water-soluble and plays a role in turning food into energy, as well as in the metabolism of fats and carbohydrates. Niacin can also act as an antioxidant within cells, which means it can destroy cell-dam-aging free radicals. In conjunction with riboflavin and pyridoxine, it helps to keep the skin, intestinal tract and nervous system functioning smoothly.

General Use

The recommended daily allowance (RDA) of niacin for infants under six months is 5 mg. Babies from six months to one year of age require 6 mg. Children need 9 mg at one to three years of age, 12 mg at four to six years, and 13 mg at seven to 10 years. Women need 15 mg from 11-50 years, and 13 mg thereafter. Somewhat more is required for pregnancy (17 mg) and lactation (20 mg). Men require 17 mg from 11-14 years of age, 20 mg from 15-18 years, 19 mg from 19-50 years, and 15 mg at 51 years and older.

Niacin in the form of nicotinic acid can be taken in very large doses to decrease blood cholesterol levels and reduce the risk of heart attack. Niacin is an important part of the treatment of familial hyperlipidemia, an inherited disorder characterized by high blood cholesterol levels and increased risk of heart disorders. The amount of niacin required is between 2 and 3 g per day. Although treatment with niacin is considered the best strategy for normalizing blood cholesterol levels as of 2002, it should not be undertaken without professional medical advice and supervision. Niacin has been singled out as a dietary supplement for which people frequently exceed the upper limits of safe intake. One Canadian study found that 47% of adults who were taking dietary supplements were taking niacin above recommended levels.

Certain conditions preclude the use of high doses of niacin. These disorders include gout, diabetes, peptic ulcer, liver or kidney disease, and high blood pressure requiring medication. Even in the absence of these conditions, a patient on high doses of niacin should be closely monitored to be sure the therapy is both effective and without complications. A frequent side effect of this therapy is extreme flushing of the face and neck. It is harmless, but can be unpleasant. An alternative form of nicotinic acid that does not cause flushing is inositol hexaniacinate. "Slow release" niacin also causes less flushing, but should not be taken as there is higher risk of liver inflammation.

There is some evidence that niacinamide used on a long-term basis can prevent the onset of juvenile diabetes in many susceptible children. Those who have been newly diagnosed with juvenile diabetes may also benefit by extending the time that the pancreas continues to produce a small amount of insulin. The advice of a health care provider should be sought for these uses.

Inositol hexaniacinate can be helpful for people suffering from intermittent claudication. This condition causes leg pain with exercise due to poor blood flow to the legs. Dilation of the blood vessels caused by the inositol hexaniacinate relieves this condition to some extent, allowing the patient to walk farther with less pain.

Other conditions that may be benefited by supplemental niacinamide include vertigo, tinnitus, premenstrual syndrome (PMS) headaches, and osteoarthritis. Raynaud's phenomenon reportedly may be improved by large doses of inositol hexaniacinate. A health care provider should be consulted for these uses. Niacin is not effective for the treatment of schizophrenia.

Preparations

Natural Sources

Tuna is one of the best sources of niacin, but many other foods contain the vitamin. Most processed grain products are fortified with niacin, as well as other B vitamins. Although niacin is not destroyed by cooking, it does leach into water, so cooking with minimal liquid best preserves it. The amino acid tryptophan is widely found in foods high in protein, and about half of the tryptophan consumed is used to make niacin. Cottage cheese, milk, fowl, and tuna are some of the foods that are highest in tryptophan.

Supplemental Sources

Niacin can be purchased as an oral single vitamin product. A balanced B complex supplement is preferred over high doses of an individual vitamin unless there is a specific indication. Supplements should be stored in a cool, dry place, away from light, and out of the reach of children.

Deficiency

A serious deficiency of niacin causes a condition called pellagra. Once quite common in all countries, it has become rare outside of areas in which poor nutrition is still the norm. Affected groups include refugees displaced by war as well as populations affected by such emergency situations as famine. The symptoms of pellagra include dermatitis, dementia, and diarrhea.

Milder deficiencies of niacin can cause similar, but less severe symptoms. Dermatitis, especially around the mouth, and other rashes may occur, along with fatigue, irritability, poor appetite, indigestion, diarrhea, headache, and possibly delirium.

Risk Factors for Deficiency

Severe niacin deficiency is uncommon in most parts of the world, but some people may need more than the RDA in order to maintain good health. Vegans, and others who do not eat animal protein, should consider taking a balanced B vitamin supplement. Others that may need extra niacin and other B vitamins may include people under high stress, including those experiencing chronic illnesses, liver disease, sprue, or poor nutritional status. People over 55 years old are more likely to have a poor dietary intake. Certain metabolic diseases also increase the requirement for niacin. Those who abuse nicotine, alcohol or other drugs are very frequently deficient in B vitamins, but use of niacin with alcohol can cause seriously low blood pressure. A health care professional can determine if supplementation is appropriate.

Precautions

Niacin should not be taken by anyone with a B vitamin allergy, kidney or liver impairment, severe hypotension, un-stable angina, arterial hemorrhage, or coronary artery disease. Supplemental niacin can exacerbate peptic ulcers. Diabetics should use caution as supplements of either niacin or niacinamide can alter medication requirements to control blood glucose. Supplements can raise uric acid levels, and aggravate gout in people with this condition. Pregnant women should not take high doses of niacin, or any supplement, except on the advice of a health care provider.

Health care should be sought immediately if certain symptoms occur following niacin supplementation. These include abdominal pain, diarrhea, nausea, vomiting, yellowing of the skin, faintness, or headache. Such symptoms may indicate excessively low blood pressure or liver problems. Heart palpitations and elevated blood sugar are also potential effects.

Side Effects

High doses of niacin can cause a harmless but un-pleasant flushing sensation as well as darkening of the urine. The "no-flush" form can lessen this complication.

Interactions

Niacin supplements should not be taken by anyone on medication for high blood pressure, due to the potential for hypotension. Isoniazid, a drug used to treat tuberculosis, inhibits the body's ability to make niacin from tryptophan. Extra niacin may be required. Supplements may also be needed by women taking oral contraceptives. Concomitant use of niacin with statin class drugs to lower cholesterol can cause myopathy. Cholestyramine and cholestipol, older medications to lower cholesterol, should be taken at a different time than niacin or they will reduce its absorption. Transdermal nicotine used with niacin is likely to cause flushing and dizziness. Carbamazepine, an antiseizure medication, is more likely to cause toxicity in combination with niacin.

Resources

Books

Bratman, Steven, and David Kroll. Natural Health Bible. Prima Publishing, 1999.

Griffith, H. Winter. Vitamins, Herbs, Minerals & supplements: the complete guide. Arizona: Fisher Books, 1998.

Jellin, Jeff, Forrest Batz, and Kathy Hitchens. Pharmacist's letter/Prescriber's Letter Natural Medicines Comprehensive Database. California: Therapeutic Research Faculty, 1999.

Pressman, Alan H., and Sheila Buff. The Complete Idiot's Guide to Vitamins and Minerals. New York: alpha books, 1997.

Periodicals

Batiste, M. C., and E. J. Schaefer. "Diagnosis and Management of Lipoprotein Abnormalities." Nutrition in Clinical Care: An Official Publication of Tufts University 5 (May-June 2002): 115-123.

Gotto, A. M. Jr. "Management of Dyslipidemia." American Journal of Medicine 112 (June 3, 2002) (Supplement 8A): 10S-18S.

Hopkins, P. M. "Familial Hypercholesterolemia." Curren Treatment OPtions in Cardiovascular Medicine 4 (April 2002): 121-128.

Prinzo, Z. W., Z. W. Prinzo, and D. Benoist. "Meeting the Challenges of Micronutrient Deficiencies in Emergency-Affected Populations." Proceedings of the Nutrition Society 61 (May 2002): 251-257.

Troppmann, L., K. Gray-Donald, and T. Johns. "Supplement Use: Is There Any Nutritional benefit?" Journal of the American Dietetic Association 102 (June 2002): 818-825.

Organizations

American Dietetic Association. 216 West Jackson Blvd., Chicago, IL 60606. (312) 899-0040. .

World Health Organization (WHO). Avenue Appia 20, 1211 Geneva 27, Switzerland. (+41 22) 791-2111. .

[Article by: Judith Turner; Rebecca J. Frey, PhD]

 

Water-soluble vitamin of the vitamin B complex, essential to growth and health in animals, including humans. It is found in the body only in combined form as a coenzyme, nicotinamide adenine dinucleotide (NAD), which is involved in the metabolism of carbohydrates and the oxidation of sugar derivatives and other substances. One of the most stable vitamins, it survives most cooking and most preserving processes. It is widely found in dietary sources, especially lean meat. Deficiency causes pellagra. It is used as a drug to reduce high cholesterol levels in the blood.

For more information on niacin, visit Britannica.com.

 

nicotinic acid; vitamin B3

A water-soluble vitamin belonging to the B-complex. It is a component of nicotinamide adenine dinucleotide). NAD and plays an important role in respiratory metabolism. When niacin is present in the blood in high concentrations it has insulin-like effects and inhibits fat mobilization. Enteric bacteria may produce some niacin in the intestine. Meat and yeast products are rich sources of niacin. Deficiency causes pellagra, characterized by diarrhoea, dermatitis, and mental disturbance.

 

A water-soluble vitamin of the B complex found in various animal and plant tissues. Essential for normal carbohydrate metabolism. Most natural animal feeds have high enough content to avoid need for supplementation, except for pigs fed a heavy corn diet. Called also nicotinic acid, vitamin PP. See also nicotinamide.

  • n. nutritional deficiency — causes hemorrhagic diarrhea, dermatitis, anemia and a severe stomatitis with ulceration of the mouth and tongue (‘black tongue’). In cats, the signs are diarrhea, emaciation and death. Called also pellagra.
  • n. production — a test for differentiating Mycobacteria tuberculosis (positive) and M. avium (negative).


 
Wikipedia: niacin
For the band, see Niacin (band).
Niacin
Niacin_structure.svg
IUPAC name nicotinic acid
Other names pyridine-3-carboxylic acid
Identifiers
CAS number 59-67-6
PubChem 937
MeSH Niacin
SMILES C1=CC(=CN=C1)C(=O)[O-]
Properties
Molecular formula C6H5NO2
Molar mass 122.102
Melting point

236.6 °C

Boiling point

decomposes

Except where noted otherwise, data are given for
materials in their standard state
(at 25 °C, 100 kPa)

Infobox disclaimer and references

Niacin, also known as nicotinic acid or vitamin B3, is a water-soluble vitamin whose derivatives such as NADH, NAD, NAD+, and NADP play essential roles in energy metabolism in the living cell and DNA repair.[1] The designation vitamin B3 also includes the corresponding amide nicotinamide (or "niacinamide"), whose chemical formula is C6H6NO2.

Other functions of niacin include removing toxic chemicals from the body,[2] and assisting in the production of steroid hormones made by the adrenal gland, such as sex hormones and stress-related hormones.

History

Niacin was first discovered from the oxidation of nicotine to form nicotinic acid. When the properties of nicotinic acid were discovered, it was thought prudent to choose a name to dissociate it from nicotine, in order to avoid the perception that vitamins or niacin-rich food contains nicotine. The resulting name 'niacin' was derived from nicotinic acid + vitamin.

Niacin is also referred to as Vitamin B3 because it was the third of the B vitamins to be discovered. It has historically been referred to as "vitamin PP", a name derived from the term "pellagra-preventing factor", because the disease pellagra is due to a deficiency of niacin in the diet.

Dietary needs

The recommended daily allowance of niacin is 2-12 mg a day for children, 14 mg a day for women, 16 mg a day for men, and 18 mg a day for pregnant or breast-feeding women.[3]

Severe deficiency of niacin in the diet causes the disease pellagra, whereas mild deficiency slows down the metabolism, causing decreased tolerance to cold.

Dietary niacin deficiency tends to occur only in areas where people eat corn (maize), the only grain low in niacin, as a staple food, and that do not use lime during meal/flour production. Alkali lime releases the tryptophan from the corn in a process called nixtamalization so that it can be absorbed in the intestine, and converted to niacin.[2]

Pharmacological uses

Niacin, when taken in large doses, blocks the breakdown of fats in adipose tissue, thus altering blood lipid levels. Niacin is used in the treatment of hyperlipidemia because it reduces very-low-density lipoprotein (VLDL), a precursor of low-density lipoprotein (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.[4]

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.[5][6] An extended release formulation of niacin for this indication is marketed by Abbott Laboratories under the trade name Niaspan.

Niacin is sometimes consumed in large quantities by people who wish to fool drug screening tests, particularly for lipid-soluble drugs such as marijuana.[7] It is believed to "promote metabolism" of the drug and cause it to be "flushed out." Scientific studies have shown it does affect drug screenings, but can pose a risk of overdose, causing arrhythmias, metabolic acidosis, hyperglycemia, and other serious problems (see below).

Toxicity

People taking pharmacological doses of niacin (1.5 - 6 g per day) often experience a syndrome of side-effects that can include one or more of the following:[8]

Facial flushing is the most commonly-reported side-effect.[9] It lasts for about 15 to 30 minutes, and is sometimes accompanied by a prickly or itching sensation. This effect is mediated by prostaglandins 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 1 to 2 weeks of a stable dose, most patients no longer flush. Slow- or "sustained"-release forms of niacin have therefore been developed to lessen these side-effects.[10][11] [12] One study showed the incidence of flushing was 4.5x lower (1.9 vs. 8.6 episodes in the first month) with a sustained-release formulation.[13]

Doses above 2 g per day have been associated with liver damage, particularly with slow-release formulations. [14]

High-dose niacin may also elevate blood sugar, thereby worsening diabetes mellitus.[15] Hyperuricemia is another side-effect of taking high-dose niacin; thus niacin may worsen gout[citation needed].

Niacin at doses used in lowering cholesterol has been associated with birth defects in laboratory animals and should not be taken by pregnant women.[16]

Niacin at extremely high doses can have life-threatening acute toxic reactions. One patient suffered vomiting after taking eleven 500-milligram niacin tablets over 36 hours, and another was unresponsive for several minutes after taking five 500-milligram tablets over two days.[17][18] Extremely high doses of niacin can also cause niacin maculopathy, a thickening of the macula and retina which leads to blurred vision and blindness.[19]

Inositol hexanicotinate

One popular form of dietary supplement is inositol hexanicotinate, usually sold as "flush-free" or "no-flush" niacin (although those terms are also used for regular sustained-release.) While this form of niacin does not cause the flushing associated with the nicotinic acid form, it is not clear whether it is pharmacologically equivalent in its positive effect [20].

Biosynthesis

The liver can synthesize niacin from the essential amino acid tryptophan (see below), but the synthesis is extremely inefficient; 60 mg of tryptophan are required to make one milligram of niacin.[21]

The 5-membered aromatic heterocycle of the essential amino acid, tryptophan, is cleaved and rearranged with the alpha amino group of tryptophan into the 6-membered aromatic heterocycle of niacin by the following reaction:

Biosynthesis: Tryptophan → kynurenine →  niacin
Enlarge
Biosynthesis: Tryptophankynurenine → niacin

Food sources

Animal products: Fruits and vegetables: Seeds: Fungi:

References

  1. ^ Northwestern University Nutrition
  2. ^ a b
  3. ^ Jane Higdon, "Niacin", Micronutrient Information Center, Linus Pauling Institute
  4. ^ T. Katzung, Basic and Clinical Pharmacology, 9th ed. p. 570.
  5. ^ Postgraduate Medicine
  6. ^ Canner PL, Berge KG, Wenger NK, et al. Fifteen year mortality in Coronary Drug Project patients: long-term benefit with niacin. J Am Coll Cardiol. 1986;8(6):1245-1255.
  7. ^ Niacin abuse in the attempt to alter urine drug tests. Pharmacist's Letter/Prescriber's Letter 2007;23(6):230606.
  8. ^ J.G. Hardman et al., eds., Goodman and Gilman's Pharmacological Basis of Therapeutics, 10th ed., p.991.
  9. ^ NIH Medline Plus: Niacin. http://www.nlm.nih.gov/medlineplus/ency/article/002409.htm.
  10. ^ J.G. Hardman et al., eds., Goodman and Gilman's Pharmacological Basis of Therapeutics, 10th ed., p.991.
  11. ^ T. Katzung, Basic and Clinical Pharmacology, 9th ed. p. 570.
  12. ^ Options for therapeutic intervention: How effective are the different agents? European Heart Journal Supplements Vol 8 Suppl F Pp. F47-F53 [1]
  13. ^ Chapman M, Assmann G, Fruchart J, Sheperd J, Sirtori C. Raising high-density lipoprotein cholesterol with reduction of cardiovascular risk: the role of nicotinic acid - a position paper developed by the European Consensus Panel on HDL-C. Cur Med Res Opin. 2004 Aug;20(8):1253-68. PubMed
  14. ^ J.G. Hardman et al., eds., Goodman and Gilman's Pharmacological Basis of Therapeutics, 10th ed., p.992.
  15. ^ J.G. Hardman et al., eds., Goodman and Gilman's Pharmacological Basis of Therapeutics, 10th ed., p.991.
  16. ^ J.G. Hardman et al., eds., Goodman and Gilman's Pharmacological Basis of Therapeutics, 10th ed., p.992.
  17. ^ Hazards: Niacin to Pass a Drug Test Can Have Dangerous Results, By ERIC NAGOURNEY, New York Times, April 17, 2007[2]
  18. ^ Mittal MK, Florin T, Perrone J, Delgado JH, Osterhoudt KC. Toxicity From the Use of Niacin to Beat Urine Drug Screening. Ann Emerg Med. 2007 Apr 4. PubMed[3]
  19. ^ JD Gass, Nictonic Acid Maculopathy, Am. J. Opthamology, 1973;76:500-10
  20. ^ No-Flush Niacin for the Treatment of Hyperlipidemia
  21. ^ Oxidization Reactions of Niacin from the Linus Pauling Institute at Oregon State University Linus Pauling Institute.

External links



 
Translations: Translations for: Niacin

Dansk (Danish)
n. - nikotinsyre

Nederlands (Dutch)
niacine/ nicotinezuur (vitamine B5)

Français (French)
n. - acide nicotinique

Deutsch (German)
n. - (chem.) Nikotinsäure

Ελληνική (Greek)
n. - νικοτινικό οξύ

Italiano (Italian)
niacina

Português (Portuguese)
n. - ácido (m) nicotínico (Biol.)

Русский (Russian)
никотиновая кислота

Español (Spanish)
n. - niacina, ácido nicotínico

Svenska (Swedish)
n. - nikotinsyra, niacin

中文(简体) (Chinese (Simplified))
烟碱酸的商品名, 尼亚新

中文(繁體) (Chinese (Traditional))
n. - 煙鹼酸的商品名, 尼亞新

한국어 (Korean)
n. - 니코틴산

日本語 (Japanese)
n. - ナイアシン

العربيه (Arabic)
‏(الاسم) الحامض النيكوتيني‏

עברית (Hebrew)
n. - ‮ניאצין (ויטמין\חומצה)‬


 
 

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