Niacin

Niacin, also known as nicotinic acid, is an organic compound and a form of vitamin B3, an essential human nutrient. It has the formula C6H5NO2 and belongs to the group of the pyridinecarboxylic acid. Niacin is obtained in the diet from a variety of whole and processed foods, with highest contents in fortified packaged foods, tuna, some vegetable and other animal sources. Some countries require its addition to grains. Supplemental niacin is primarily used to treat high blood cholesterol and pellagra (niacin deficiency). Not enough niacin can cause nausea, skin and mouth lesions, anemia, headaches, and tiredness. This lack of niacin may also be observed in pandemic deficiency diseases, which are caused by a lack of five crucial vitamins (niacin, vitamin C, thiamin, vitamin D, and vitamin A) and are usually found in areas of widespread poverty and malnutrition. Niacin supplementation has not been found useful for decreasing the risk of cardiovascular disease in those already on a statin, but appears to be effective in those not taking a statin. Although niacin and nicotinamide are identical in their vitamin activity, nicotinamide does not have the same pharmacological effects (lipid-modifying effects) as niacin. Nicotinamide does not reduce cholesterol or cause flushing. As the precursor for NAD and NADP, niacin is also involved in DNA repair. In 2016 it was the 277th most prescribed medication in the United States with more than a million prescriptions.It has the European food additive series E number of E375. Niacin and niacinamide are used for prevention and treatment of pellagra. Niacin has sometimes been used in addition to other lipid-lowering medications. Systematic reviews found no effect of niacin on cardiovascular disease or death, in spite of raising HDL cholesterol, and reported side effects including an increased risk of diabetes. Niacin is contraindicated with active liver disease, persistent elevated serum transaminases, active peptic ulcer disease, or arterial bleeding. The most common adverse effects of niacin at relatively low doses (50–500 mg) are flushing (e.g., warmth, redness, itching or tingling), headache, abdominal pain, diarrhea, dyspepsia, nausea, vomiting, rhinitis, pruritus and rash. These can be minimized by initiating therapy at low dosages, increasing dosage gradually, and avoiding administration on an empty stomach. The acute adverse effects of high-dose niacin therapy (1–3 grams/day) – which is commonly used in the treatment of hyperlipidemias – further include hypotension, fatigue, glucose intolerance and insulin resistance, heartburn, blurred or impaired vision, and macular edema. With long-term use, the adverse effects of high-dose niacin therapy also include hepatic dysfunction (associated with fatigue, nausea, and loss of appetite), hepatitis, and acute liver failure; these hepatotoxic effects of niacin occur more often when extended-release dosage forms are used. The long-term use of niacin at high doses (2 grams/day) also significantly increases the risk of cerebral hemorrhage, ischemic stroke, gastrointestinal ulceration and bleeding, diabetes, dyspepsia, and diarrhea.