Niacin and Blood Pressure

Niacin, also known as vitamin B3 or nicotinic acid, is a colorless, water-soluble organic compound with the formula C5H4NCO2H. This vitamin is essential for various biochemical processes to take place in the body, one being the metabolism of fat. Niacin may also lower blood pressure, particularly at higher doses administered over a longer period of time. Additionally, there is another common form of B3 called niacinamide.

See also: Herbs for High Blood Pressure

How Does Niacin Work?

Niacin and the lowering of blood pressure

Immediate-release niacin may lower blood pressure because of its vasodilatory effects. Some clinical studies have found that niacin may lower BP when administered over an extended period of time. Niacin activates the G protein-coupled GPR109A receptors on cells such as adipocytes, which may impact on lipid metabolism. These receptors are also found on epidermal Langerhans cells in the skin, and generate prostaglandins such as PGD2, which in turn, stimulate PGD2 type 1 (PD1) receptors on vascular smooth-muscle cells in dermal arterioles, resulting in vasodilatation and flushing. GPR109A activation on Langerhans cells may also produce PGE2 and possibly other mediators that could potentially influence vascular tone and thus may also contribute to a lowering of blood pressure. Additionally, niacin could potentially activate its receptor on other cell types (including other components of the cardiovascular system) that could lead to haemodynamic changes. Additionally, niacin could have other effects (not mediated by GPR109A) that could have a positive impact on high blood pressure.

Niacin and the lowering of cholesterol and triglycerides

Niacin is recommended by some experts to help lower low-density lipoprotein (LDL) or bad cholesterol levels within the body. Because of its ability to promote the break down of fats niacin has a potential role to play in the prevention and treatment of cardiovascular disease. Some cardiologists prescribe 3 grams of niacin per day or even higher amounts for patients with very high cholesterol levels. Unfortunately, at this high level, niacin has negative side effects. It should be noted that numerous studies have shown that for 67% of patients a dose of 3,000 mgs or more of daily niacin still did not promote the lowering of cholesterol. Additionally, the other form of Vitamin B3, niacinamide had no effect on cholesterol what so ever.

Other studies involving pharmacological doses of niacin have indicated that it can reverse atherosclerosis by reducing total cholesterol, triglyceride, very-low-density lipoprotein (VLDL), and LDL; and increase high-density lipoprotein (HDL). It has been proposed that niacin has the ability to lower lipoprotein(a) which is beneficial in reducing thrombotic tendency.

Niacin, prescribed at doses between 1000 and 2000 mg taken two to three times daily, blocks the breakdown of fats in adipose tissue, more specifically VLDL, the precursor of LDL. Because niacin blocks the breakdown of fats, it results in a decrease in free fatty acids in the blood and, as a consequence, decreased secretion of VLDL and cholesterol by the liver.

By lowering VLDL levels, niacin also increases the level of HDL or “good” cholesterol in the blood, and therefore it is sometimes prescribed for patients with low HDL, that are also at high risk of a heart attack.

Niacin side effects

When used at lower doses, such as those found in a daily multi-vitamin (20 mg daily = 100% of RDA), niacin is very safe. However, pharmacological doses of niacin (1.5 – 6 g per day) often result in side effects that include:

Dermatological effects: Skin flushing due to dilation of blood vessels lasting about 15 to 30 minutes and itching, dry skin, skin rashes. Skin flushing is mediated by prostaglandin and can be blocked by ingesting 300 mg of aspirin about 30 minutes before taking niacin, or by taking one tablet of ibuprofen per day. Taking niacin with meals also helps to diminish this side effect. One clinical study demonstrated that the incidence of flushing was significantly lower with a sustained release niacin formulation, although doses above 2 g per day have been associated with liver damage, particularly with slow-release formulations.

Gastrointestinal effects: Dyspepsia (indigestion) and liver toxicity (fulminant hepatic failure).

Elevated blood sugar: High-dose niacin may also elevate blood sugar, thereby worsening diabetes mellitus.

Gout: Hyperuricemia is another side effect of taking high-dose niacin, and may exacerbate gout.

Birth defects: Niacin used at pharmacological doses has been associated with birth defects in laboratory animals, with possible consequences for infant development in pregnant women.

Maculopathy: Niacin taken at extremely high doses can also cause maculopathy, a thickening of the macula and retina which leads to blurred vision and blindness. This can be reversed by terminating niacin intake.

Also, avoid alcohol or hot beverages near the time of the niacin dose.

How to take niacin

Take this medication with food to prevent stomach upset. Follow any special dietary recommendations made by a doctor or nutritionist while taking this medication. If prescribed bile acid resin drugs (e.g. colestipol, cholestyramine) leave at least a 6 hours before taking niacin. Since alcohol can intensify drug side effects, ask a doctor or pharmacist about drinking alcohol while taking high dose niacin. If niacin is being used as a cholesterol treatment, breast-feeding is not recommended due to possible infant side effects. Consult a doctor before you breast-feeding.

Niacin dosage

The recommended daily dose 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. The upper limit for adult men and women is 35 mg/day which is based on flushing as the critical side effect, at 10 to 20 minutes after niacin is taken.

Niacin drug interactions

Inform a doctor if taking over-the-counter or prescription drugs especially: high blood pressure drugs, diabetes medicine, fibrates (e.g. gemfibrozil, fenofibrate) or statins (e.g. lovastatin, atorvastatin). If taking insulin or oral diabetes medication, the dosage may need to be altered due to increased blood sugar levels caused by niacin. Do not start or stop any medicine without doctor or pharmacist approval.

Niacin in food

Niacin is found in variety of foods including liver, chicken, beef, fish, cereal, nuts, mushrooms, brewer’s yeast, avocados, dates, tomatoes, leaf vegetables, broccoli, carrots, sweet potatoes, asparagus, dairy products and eggs.

NOTE: This information is given for educational purposes only and should not be used for the diagnosis, treatment or prevention of disease. It should not be used to replace the services of a qualified practitioner.