Niacin

Niacin is one form of vitamin B3. Niacinamide and inositol hexanicotinate are the other two forms of B3 that exist; these forms are generally used to treat different conditions within the body. B vitamins ultimately help the body utilize fats and proteins; they also help convert food into fuel which is then used to produce energy.^[1] B vitamins are water-soluble by nature; niacin can be absorbed easily when taken with or dissolved in water.^[2] Common food sources of niacin include eggs, bran, peanuts, meat, poultry, fish, legumes, seeds, cereal grains, and yeast. Most people are easily able to meet the body’s needs for B3 through diet alone.^[3]

Deficiency

Alcoholism and gastrointestinal disease are the main causes of niacin deficiency in the developed world.^[4] Symptoms of mild deficiency include indigestion, fatigue, canker sores, vomiting, and depression.^[1] Niacin deficiency can also cause an uncommon condition known as pellagra. Pellagra is virtually nonexistent in Western countries, but is still an issue in some developing countries of the world.^[2] Pellagra is characterized by the “3 D” symptoms of dermatitis, dementia, and diarrhea. This condition may also progress to a state of death. The dermatitis of pellagra is symmetrical and found in areas that are exposed to the sun. Pellagra dermatitis resembles second-degree burns, with the formation of vesicles and bullae. Meanwhile, stools are watery, and blood or mucus may also be present. Dementia often presents as confusion, disorientation, and delirium.^[3]

Side Effects

The most common side effect of taking niacin is flushing. Symptoms of flushing include burning, itching, tingling, along with redness in the affected areas. The flushing reaction generally causes discomfort and can be minimized, or even possibly avoided, once the body gets used to taking niacin regularly. Alcohol is known to make the flushing reaction worse; it is therefore not recommended to drink alcohol while taking niacin supplements.^[2] Meanwhile, high doses of niacin (greater than 3 g/d) can cause serious side effects, including liver damage, gout, GI ulcers, stomach upset, high blood sugar, loss of vision, dizziness, headaches, and/or irregular heartbeat.^[2]

Therapeutic Uses
Cardiovascular Disease

Studies show that niacin has a beneficial effect on blood lipid levels. In one randomized controlled trial, 3414 patients taking statin drugs were assigned to also receive either niacin (1718 participants) or placebo (1696 participants). Niacin was shown to have an overall improvement; it raised HDL cholesterol levels by 25% following two years of continuous use, whereas HDL levels had only increased 9.8% in the placebo group. In addition, it was found that triglyceride levels decreased by 28.6% in the niacin group and by 5.5% in the placebo group. Extended-release niacin plus simvastatin, as compared to simvastatin alone, was associated with significant increases in HDL cholesterol and decreases in triglyceride levels.^[5] Niacin is currently the most effective therapy available for the treatment of low HDL cholesterol. Similarly, another study also showed an increase in HDL cholesterol levels for those taking niacin following 12 months; HDL-C levels remained unchanged for the placebo group. Triglyceride levels decreased significantly. In addition, carotid-intima media thickness was significantly increased in the placebo group. It therefore appears as though niacin was able to slow the progression of atherosclerosis among individuals with known coronary heart disease.^[6] An additional study investigated the use of extended-release niacin (N) in combination with ezetimide and simvastatin (E/S). This study occurred over the course of 24 weeks, and 1220 hyperlipidemic participants were randomized to one of the following groups of interventions: E/S and N (combination), N, or E/S. Coadministered E/S and N resulted in significantly greater reductions in LDL cholesterol compared to either therapy alone. Also, HDL-C levels were significantly higher in the combination group and high-sensitivity C-reactive protein (hs-CRP) levels were reduced.^[7] The level of CRP rises in the blood when there is inflammation present throughout the body.^[8]

Alzheimer’s Disease

Niacin has clearly established relations with deterioration of mental state. A large prospective study examined whether dietary intake of niacin was associated with Alzheimer’s disease. Cognitive tests were administered to study participants at three-year intervals in a six-year follow-up. Nutrient intake was determined by food-frequency questionnaires. Niacin appeared to have a protective effect on the development of Alzheimer’s and cognitive decline; intake from foods was inversely associated with Alzheimer’s. The study concluded that higher food intake was associated with a slower annual rate of cognitive decline.^[4] Meanwhile, Glen Green, M.D., took the time to acknowledge the mental symptoms in patients with vitamin B3 deficiency, who all responded well to treatment with niacin supplements.^[9] Lastly, researchers at the Rush Institute for Healthy Aging in Chicago followed the diets of over 3,500 people 65 years of age and older for 5½ years: results revealed that those who got the least amount of niacin were 70 percent more likely to have Alzheimer’s disease; participants who took niacin supplements and ate niacin-rich foods showed less cognitive decline.^[10]

Dermatology

Niacin appears to be beneficial for a variety of skin conditions; it is found in a variety of skin creams for this very reason. Niacin appears to have protective effects against skin damage induced by ultraviolet (UV) radiation. Niacin effectively suppresses UV-induced cell death and apoptosis in human skin keratinocytes. Apoptosis is the process of programmed cell death, which involves a series of morphological changes within the cell. In one study, UV treatment caused a significant decrease in cell viability; meanwhile, cell viability was markedly recovered in the presence of niacin. Improvements in cell viability occurred alongside graded increases in niacin concentrations.^[11] Niacin is water-soluble and thus has difficulty crossing the fat-soluble skin barrier. However, when niacin’s fatty esters cross the skin barrier, they increase skin nicotinamide adenine dinucleotide (NAD) levels; an increase in NAD improves skin thickness and barrier function, which in turn improves immune defenses and function.^[12]

Conclusion

There are many suggested uses for niacin, but only a select few were touched upon. Evidence shows that niacin is useful for lowering blood lipid levels and increasing HDL cholesterol. Niacin may also be good for the treatment of skin conditions and prevention of Alzheimer’s disease. Niacin is a relatively uncommon deficiency in the western world. A niacin deficiency can cause pellagra, which can be life-threatening. Niacin supplements should be used with caution as severe side effects can occur, including liver damage.