However, niacin is only effective as a cholesterol treatment at fairly high doses. These doses could pose risks, such as liver damage, gastrointestinal problems, or glucose intolerance. So don't treat yourself with over-the-counter niacin supplements. Instead, get advice from your health care provider, who can prescribe FDA-approved doses of niacin instead if recommended. Both niacin and niacinamide are rapidly absorbed from the stomach and small intestine. [77] Absorption is facilitated by sodium-dependent diffusion, and at higher intakes, via passive diffusion. Unlike some other vitamins, the percent absorbed does not decrease with increasing dose, so that even at amounts of 3-4 grams, absorption is nearly complete. [20] With a one gram dose, peak plasma concentrations of 15 to 30 μg/mL are reached within 30 to 60 minutes. Approximately 88% of an oral pharmacologic dose is eliminated by the kidneys as unchanged niacin or nicotinuric acid, its primary metabolite. The plasma elimination half-life of niacin ranges from 20 to 45 minutes. [23]

Tolerable Upper Intake Levels For Vitamins And Minerals" (PDF). European Food Safety Authority. 2006. Archived (PDF) from the original on 16 March 2016 . Retrieved 9 March 2016. Wit B3 to w rzeczywistości dwa związki chemiczne – kwas nikotynowy oraz nikotynamid (niacynamid). Wykazują one zbliżoną aktywność biologiczną, czyli działanie na organizm, gdyż kwas nikotynowy w procesach metabolicznych może zostać przekształcony do nikotynamidu. Niacin is also a prescription medication. [11] Amounts far in excess of the recommended dietary intake for vitamin functions will lower blood triglycerides and low density lipoprotein cholesterol (LDL-C), and raise blood high density lipoprotein cholesterol (HDL-C, often referred to as "good" cholesterol). There are two forms: immediate-release and sustained-release niacin. Initial prescription amounts are 500mg/day, increased over time until a therapeutic effect is achieved. Immediate-release doses can be as high as 3,000mg/day; sustained-release as high as 2,000mg/day. [11] Despite the proven lipid changes, niacin has not been found useful for decreasing the risk of cardiovascular disease in those already on a statin. [12] A 2010 review had concluded that niacin was effective as a mono-therapy, [13] but a 2017 review incorporating twice as many trials concluded that prescription niacin, while affecting lipid levels, did not reduce all-cause mortality, cardiovascular mortality, myocardial infarctions, nor fatal or non-fatal strokes. [14] Prescription niacin was shown to cause hepatotoxicity [15] and increase risk of type 2 diabetes. [16] [17] Niacin prescriptions in the U.S. had peaked in 2009, at 9.4 million, [ citation needed] declining to 800 thousand by 2020. [18] a b c "Overview on Dietary Reference Values for the EU population as derived by the EFSA Panel on Dietetic Products, Nutrition and Allergies" (PDF). 2017. Archived (PDF) from the original on 28 August 2017 . Retrieved 31 August 2017. That said, deficiency is very rare in most Western countries. People who are malnourished — which may stem from HIV/AIDS, anorexia nervosa, liver failure, alcohol abuse, or other medical problems, or poverty — are most at risk.Chai JT, Digby JE, Choudhury RP (May 2013). "GPR109A and vascular inflammation". Current Atherosclerosis Reports. 15 (5): 325. doi: 10.1007/s11883-013-0325-9. PMC 3631117. PMID 23526298.

Pesticides (e.g., alternariol, dieldrin, endosulfan, fenarimol, HPTE, methiocarb, methoxychlor, triclocarban, triclosan) Altschul R, Hoffer A, Stephen JD (February 1955). "Influence of nicotinic acid on serum cholesterol in man". Archives of Biochemistry and Biophysics. 54 (2): 558–9. doi: 10.1016/0003-9861(55)90070-9. PMID 14350806. The acute adverse effects of high-dose niacin therapy ( 1–3grams per day) – which is commonly used in the treatment of hyperlipidemias– can further include hypotension, fatigue, glucose intolerance and insulin resistance, heartburn, blurred or impaired vision, and macular edema. [3] [5] With long-term use, the adverse effects of high-dose niacin therapy (750mg per day) also include liver failure (associated with fatigue, nausea, and loss of appetite), hepatitis, and acute liver failure; [3] [5] these hepatotoxic effects of niacin occur more often when extended-release dosage forms are used. [3] [5] The long-term use of niacin at greater than or equal to 2grams per day also significantly increases the risk of cerebral hemorrhage, ischemic stroke, gastrointestinal ulceration and bleeding, diabetes, dyspepsia, and diarrhea. [5] Flushing [ edit ]Niacin is water-soluble, so your body does not store it. This also means that your body can excrete excess amounts of the vitamin through urine if they are not needed ( 1). Malik S, Kashyap ML (November 2003). "Niacin, lipids, and heart disease". Curr Cardiol Rep. 5 (6): 470–6. doi: 10.1007/s11886-003-0109-x. PMID 14558989. S2CID 27918392. Palawaththa, S., Islam, R. M., Illic, D., Rabel, K., Lee, M., Romero, L., Leung, X. Y., & Karim, Md. N. (2022). Effect of maternal dietary niacin intake on congenital anomalies: A systematic review and meta-analysis. European Journal of Nutrition, 61(3), 1133–1142. https://doi.org/10.1007/s00394-021-02731-9

Niacin in medicinal doses can cause modest elevations in serum transaminase and unconjugated bilirubin, both biomarkers of liver injury. The increases usually resolve even when drug intake is continued. [15] [70] [71] However, less commonly, the sustained release form of the drug can lead to serious hepatotoxicity, with onset in days to weeks. Early symptoms of serious liver damage include nausea, vomiting and abdominal pain, followed by jaundice and pruritus. The mechanism is thought to be a direct toxicity of elevated serum niacin. Lowering dose or switching to the immediate release form can resolve symptoms. In rare instances the injury is severe, and progresses to liver failure. [15] Diabetes [ edit ] Nutritional Yeast Flakes (two tablespoons = 16 grams". NutritionData.Self.com. Archived from the original on 11 April 2020 . Retrieved 13 May 2020. Casal G (1945). "The natural and medical history of the principality of the Asturias". In Major RH (ed.). Classic Descriptions of Disease (3rded.). Springfield: Charles C Thomas. pp.607–12. Vitamin B3 (Niacin)". VivaHealth.org. 2000. Archived from the original on 4 August 2020 . Retrieved 12 May 2020. It also takes high doses of niacin, typically 1,500 mg or greater, to achieve blood fat level improvements, which increases the risk of experiencing unpleasant or potentially harmful side effects ( 6).

W 1981 r. zaobserwowano, że codzienne przyjmowanie niacyny w dawce 3 × 1 g przez 5 tygodni doprowadziło do spadku poziomu cholesterolu o 22% [27]. Side effects. Niacin can cause flushing, especially when you first begin taking it. Your health care provider will probably suggest increasing the dose slowly to reduce this problem. They might also offer a time-release prescription formulation to control flushing. Niacin can cause upset stomach and diarrhea. However, all of these side effects tend to fade over time. The mechanism behind niacin increasing HDL-C is not totally understood, but seems to occur in various ways. Niacin increases apolipoprotein A1 levels by inhibiting the breakdown of this protein, which is a component of HDL-C. [54] [55] It also inhibits HDL-C hepatic uptake by suppressing production of the cholesterol ester transfer protein (CETP) gene. [47] It stimulates the ABCA1 transporter in monocytes and macrophages and upregulates peroxisome proliferator-activated receptor gamma, resulting in reverse cholesterol transport. [56] Combined with statins [ edit ] In one observational study of over 12,000 adults, researchers found that each 1 mg increase in daily niacin intake was associated with a 2% decrease in high blood pressure risk — with the lowest overall high blood pressure risk seen at a daily niacin intake of 14.3 to 16.7 mg per day ( 8). Adequate Intake (AI): when there is not enough evidence to develop an RDA, the AI is set at a level that is thought to ensure enough nutrition.