Niacin is a water-soluble vitamin necessary for many aspects of health, growth, and reproduction. It is part of the vitamin B complex.

Niacin assists in the functioning of the digestive system, skin, and nerves. It is also important for the conversion of food to energy.

Niacin (also known as vitamin B-3) is found in dairy products, poultry, fish, lean meats, nuts, and eggs. Legumes and enriched breads and cereals also supply some niacin.

A deficiency of niacin causes pellagra. The symptoms include inflamed skin, digestive problems, and mental impairment.

Large doses of niacin can cause liver damage, peptic ulcers, and skin rashes. Even normal doses can be associated with skin flushing. It can be prescribed as a treatment for elevated total cholesterol and other types of lipid disorders, but it should only be used with medical supervision due to its potential for severe side effects.

Recommended daily allowances (RDAs) are defined as the levels of intake of essential nutrients that the Food and Nutrition Board judges to be adequate to meet the known nutrient needs of most healthy persons.

The best way to get the daily requirement of essential vitamins is to eat a balanced diet that contains a variety of foods from the food guide pyramid.

Specific recommendations for each vitamin depend on age, gender, and other factors (such as pregnancy). The U.S. Department of Agriculture has a PDF file that lists these recommendations.