Niacin, also known as vitamin B3, is a nutrient that supports the function of the entire body. As a water-soluble vitamin, it isn’t stored and must be regularly consumed through diet. Your body gets niacin from food but also produces small amounts from the amino acid tryptophan. The vitamin has two primary chemical forms, nicotinic acid and niacinamide, which are both found in foods and supplements.
The Role of Niacin in the Body
Niacin’s primary role is supporting metabolism by helping convert food into usable energy. It is a component of the coenzymes nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP). These coenzymes are involved in over 400 biochemical reactions, mainly related to energy production from carbohydrates, fats, and proteins.
Beyond energy metabolism, niacin contributes to the health of the nervous and digestive systems. The coenzymes NAD and NADP are active in all bodily tissues, participating in cellular processes like cell signaling and DNA creation and repair. Niacin also functions as an antioxidant, helping protect cells from damage.
Top Food Sources of Niacin
Animal-Based Sources
Animal products are among the most concentrated sources of niacin. Top animal-based sources include:
- Cooked chicken breast
- Tuna, especially light tuna packed in water
- Beef, with beef liver being a particularly rich source
- Pork
- Salmon and turkey
- Eggs, which also provide tryptophan that the body can convert into niacin
Plant-Based Sources
A variety of plant-based foods contain niacin, making it accessible for those following vegetarian or vegan diets. Notable plant sources include:
- Mushrooms, such as portobello
- Peanuts and roasted peanuts
- Whole grains, such as brown rice and whole wheat bread
- Legumes, including lentils and green peas
- Avocados
- Potatoes, particularly with the skin on
Daily Niacin Requirements and Deficiency
The Recommended Dietary Allowance (RDA) for niacin is expressed in milligrams of niacin equivalents (NE). This unit accounts for niacin obtained from food and from the body’s conversion of tryptophan. For adults 19 and older, the RDA is 16 mg NE for men and 14 mg NE for women. Pregnant and lactating women have slightly higher needs, at 18 mg NE and 17 mg NE, respectively.
A severe niacin deficiency leads to a condition known as pellagra. This disease is rare in industrialized nations due to the fortification of foods like cereals but can still occur. Pellagra is characterized by symptoms often called the “three Ds”: dermatitis, diarrhea, and dementia.
The dermatitis typically appears as a dark, scaly rash on skin exposed to sunlight. Digestive issues can manifest as constipation or diarrhea and a bright red tongue. Neurological symptoms may include depression, fatigue, memory loss, headaches, and in severe cases, hallucinations.
Niacin from Food vs. Supplements
For most people, a balanced diet provides sufficient niacin to meet the body’s needs. While getting niacin from food is safe, high-dose supplements can pose risks. Niacin toxicity from food sources is not a concern, but supplements can cause adverse effects like the “niacin flush,” a reaction from 30-50 mg or more that causes reddening, itching, or a burning sensation on the skin.
Higher doses of niacin supplements can lead to more serious health issues, including stomach upset, headaches, and potential liver damage. For this reason, high-dose niacin, often as nicotinic acid, is sometimes used as a prescription medication to manage high cholesterol. This type of supplementation should only be taken under a doctor’s supervision.