Vitamin B3, also known as niacin, is found in beef liver and kidney, dairy products, beets and brewer's yeast. Additionally, many grain products, such as bread and cereals, are fortified with niacin.
Niacin is also found in many types of fish, including salmon, tuna and swordfish. Anchovies have a particularly high niacin content. Legumes, such as peanuts, can be a good source, as can sunflower seeds. Nuts can also be a niacin-rich snack. Some soy products, such as soy milk, are fortified with niacin.
Poultry and lean meats are a good source of niacin in general. Foods that contain tryptophan, such as turkey, can be a good indirect source. Tryptophan is an amino acid that is converted to niacin by the body. Although beef liver is often recommended, liver meat from chicken, turkey and pork also contains significant levels of niacin.
Niacin is also widely available in the form of supplemental pills, but these should only be taken after consulting with a doctor. Large doses of niacin can cause adverse side effects, including flushing, itchiness and a burning or tingling sensation. Niacin can also be dangerous for people with certain health conditions, including diabetes, low blood pressure, liver or kidney disease and stomach ulcers. It can also interact with many medications, including common antibiotics.