For more than 40 years, niacin in the form of nicotinic acid has been given to patients to treat a condition called dyslipidemia, a major risk factor for cardiovascular diseases CVD such as coronary artery disease, heart attack, and strokes.
Nicotinic acid supplements contain high amounts, up to 1,, mg of niacin taken daily. However, negative side effects skin flushing, stomach upset, diarrhea usually accompany the supplements, resulting in poor compliance from patients. Clinical trials have not consistently shown that nicotinic acid leads to less cardiovascular events or deaths from CVD. A severe niacin deficiency has been associated with cognitive decline such as memory loss and dementia.
Niacin is believed to protect brain cells from stress and injury. It is not yet clear though if smaller variations in dietary niacin intake can negatively affect brain function. Niacin is available as a supplement in the form of nicotinic acid or nicotinamide. Sometimes the amounts in supplements are far beyond the RDA, causing unpleasant side effects of flushing. Niacin supplements are also available as a prescription medicine that is used to treat high cholesterol; this typically comes in an extended release form of nicotinic acid that allows slower, more gradual absorption so that it does not cause flushing.
Because of the very high doses of nicotinic acid needed, up to 2, mg daily, this supplement should only be used when monitored by a physician. A niacin deficiency is rare in the United States and other industrialized countries because it is well-absorbed from most foods with the exception of some cereal grains in which niacin is bound to its fibers, decreasing the absorption and is added to many foods and multivitamins.
Other signs of severe niacin deficiency include:. Toxicity when eating foods containing niacin is rare, but can occur from long-term use of high-dose supplements. A reddened skin flush with itchiness or tingling on the face, arms, and chest is a common sign. Flushing occurs mainly when taking high-dosage supplements in the form of nicotinic acid, rather than nicotinamide. B Vitamins Vitamins and Minerals. The contents of this website are for educational purposes and are not intended to offer personal medical advice.
However, if you are deficient or have another condition that may benefit from higher doses, your doctor may recommend a supplement. In particular, niacin supplements may be recommended for people with high cholesterol and heart disease risk factors but cannot take statins. Since large amounts have many possible side effects, consult with a healthcare professional before taking niacin as part of any supplement.
Also, keep in mind that the FDA does not regulate supplements in the same way it does drugs Niacin supplements may be recommended for certain conditions. However, they can have negative side effects, so you should always discuss with your healthcare provider before taking niacin. Niacin is one of eight B vitamins that are important for every part of your body.
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What is niacin? How does it work? How much do you need? Top food sources. Safety and side effects. Nicotinic acid treatment was associated with a significantly higher risk of gastrointestinal and musculoskeletal adverse events. In addition, four of the studies that examined diabetes as an outcome found that the patients taking niacin had a significantly higher risk of developing the disease.
In their guidelines for lowering blood cholesterol levels, the American College of Cardiology and the American Heart Association advise that nonstatin therapies, compared with or in addition to statin therapy, do not provide atherosclerotic cardiovascular disease risk-reduction benefits that outweigh the potential harms of their adverse effects [ 28 ].
Their joint statement about monitoring supplement users who take niacin to reduce hyperlipidemia risk for adverse effects is described in the Health Risks from Excessive Niacin section below.
In their report, these two professional societies stated what although niacin may be useful in some cases of severe hypertriglyceridemia, it has only mild LDL-lowering effects. The societies therefore do not recommend using it as an add-on drug to statin therapy [ 34 ].
Overall, the evidence indicates that nicotinic acid supplementation improves blood lipid profiles but has no significant effects on risk of cardiovascular events. Although nicotinic acid is a nutrient, if very high doses thousands of mg are taken to treat hyperlipidemias, the supplement is being used as a drug.
Such doses should only be taken with medical approval and supervision. No adverse effects have been reported from the consumption of naturally occurring niacin in foods [ 2 ]. However, high intakes of both nicotinic acid and nicotinamide taken as a dietary supplement or medication can cause adverse effects, although their toxicity profiles are not the same. The flushing is accompanied by burning, tingling, and itching sensations [ 2 , 12 , 35 ].
These signs and symptoms are typically transient and can occur within 30 minutes of intake or over days or weeks with repeated dosing; they are considered an unpleasant, rather than a toxic, side effect. Supplement users can reduce the flushing effects by taking nicotinic acid supplements with food, slowly increasing the dose over time, or simply waiting for the body to develop a natural tolerance.
Many of these effects have occurred in patients taking high-dose nicotinic acid supplements to treat hyperlipidemias. These adverse effects can include hypotension severe enough to increase the risk of falls; fatigue; impaired glucose tolerance and insulin resistance; gastrointestinal effects, such as nausea, heartburn, and abdominal pain; and ocular effects, such as blurred or impaired vision and macular edema a buildup of fluid at the center of the retina.
High doses of nicotinic acid taken over months or years can also be hepatotoxic; effects can include increased levels of liver enzymes; hepatic dysfunction resulting in fatigue, nausea, and anorexia; hepatitis; and acute liver failure [ 2 , 12 , 28 , 36 ]. Hepatotoxicity is more likely to occur with the use of extended-release forms of nicotinic acid [ 12 , 37 , 38 ]. To minimize the risk of adverse effects from nicotinic acid supplementation or to identify them before they become serious, the American College of Cardiology and the American Heart Association recommend measuring hepatic transaminase, fasting blood glucose or hemoglobin A1C, and uric acid levels in all supplement users before they start therapy, while the dose is being increased to a maintenance level, and every 6 months thereafter [ 28 ].
The societies also recommend that patients not use nicotinic acid supplements or stop using them if their hepatic transaminase levels are more than two or three times the upper limits of normal; if they develop persistent hyperglycemia, acute gout, unexplained abdominal pain, gastrointestinal symptoms, new-onset atrial fibrillation, or weight loss; or if they have persistent and severe skin reactions, such as flushing or rashes.
Nicotinamide does not cause skin flushing and has fewer adverse effects than nicotinic acid, and these effects typically begin with much higher doses [ 12 ]. The FNB has established ULs for niacin that apply only to supplemental niacin for healthy infants, children, and adults [ 2 ].
These ULs are based on the levels associated with skin flushing. The FNB acknowledges that although excess nicotinamide does not cause flushing, a UL for nicotinic acid based on flushing can prevent the potential adverse effects of nicotinamide [ 2 ]. The UL, therefore, applies to both forms of supplemental niacin.
However, the UL does not apply to individuals who are receiving supplemental niacin under medical supervision [ 2 ]. Niacin can interact with certain medications, and several types of medications might adversely affect niacin levels.
A few examples are provided below. Individuals taking these and other medications on a regular basis should discuss their niacin status with their healthcare providers. In addition, isoniazid can interfere with niacin's conversion to NAD [ 42 ]. Although pellagra can occur in patients with tuberculosis treated with isoniazid, it can be prevented with increased intakes of niacin.
Antidiabetes medications Large doses of nicotinic acid can raise blood glucose levels by causing or aggravating insulin resistance and increasing hepatic production of glucose [ 42 ]. Some studies have found that nicotinic acid doses of 1. People who take any antidiabetes medications should have their blood glucose levels monitored if they take high-dose nicotinic acid supplements concomitantly because they might require dose adjustments [ 42 ].
The federal government's — Dietary Guidelines for Americans notes that "Because foods provide an array of nutrients and other components that have benefits for health, nutritional needs should be met primarily through foods. In some cases, fortified foods and dietary supplements are useful when it is not possible otherwise to meet needs for one or more nutrients e. For more information about building a healthy dietary pattern, refer to the Dietary Guidelines for Americans and the U.
Department of Agriculture's MyPlate. This fact sheet by the Office of Dietary Supplements ODS provides information that should not take the place of medical advice.
We encourage you to talk to your healthcare providers doctor, registered dietitian, pharmacist, etc. Any mention in this publication of a specific product or service, or recommendation from an organization or professional society, does not represent an endorsement by ODS of that product, service, or expert advice. Updated: March 26, History of changes to this fact sheet.
Find ODS on:. Strengthening Knowledge and Understanding of Dietary Supplements. Health Information Health Information. Niacin Fact Sheet for Health Professionals. Present Knowledge in Nutrition, 10th ed. Washington, DC: Wiley-Blackwell; Institute of Medicine. Food and Nutrition Board. Kirkland JB. Modern Nutrition in Health and Disease, 11th ed.
Bourgeois C, Moss J. Encyclopedia of Dietary Supplements, 2nd ed. Gibson, RS. Principles of Nutritional Assessment, Second Edition. New York: Oxford University Press. Copyright Methods in Enzymology ; Biochemical assessment of niacin deficiency among carcinoid cancer patients.
American Journal of Gastroenterology ; Biochemical markers for assessment of niacin status in young men: Levels of erythrocyte niacin coenzymes and plasma tryptophan. J Nutr ; Department of Agriculture, Agricultural Research Service. FoodData Central , Food and Drug Administration. National Institutes of Health. Dietary Supplement Label Database. Niacin: chemical forms, bioavailability, and health effects. Nutr Rev ; Journal of Clinical Lipidology ;
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