What is niacin (vitamin B3)?
Niacin, also known as vitamin B3, is an essential vitamin that performs many functions in the body. It is a water-soluble vitamin like the other B vitamins, which means that it is not readily stored in the body and needs to be consumed on a regular basis to ensure optimal health outcomes. There are many forms of niacin, including nicotinic acid, nicotinamide, and nicotine riboside.
Where is niacin found?
Niacin can be found in many foods. Some plant-based sources of niacin include grains, legumes, and nuts. Bread and breakfast cereals are often fortified with extra niacin, so those can also be a good source. Some animal-derived sources of vitamin B3 include poultry, fish, and beef.
In addition, niacin can be synthesized from the amino acid tryptophan in the body at a ratio of about one to 60, so consuming foods rich in tryptophan can provide a source of niacin. Some foods rich in tryptophan include turkey, eggs, dairy products, tofu, peanuts, and seeds. Finally, niacin can be found in multivitamins, B-complex vitamins, and niacin supplements.
Why is niacin important?
Niacin plays many important roles in health maintenance. Niacin is converted to the enzyme nicotinamide adenine dinucleotide (NAD), which catalyzes over 400 biochemical reactions in the body. In particular, this enzyme focuses on catabolic reactions, which means that they break larger, more complex compounds into smaller, simpler compounds. One example is breaking down carbohydrates, fat, and protein into smaller molecules to provide energy to the cells.
NAD is also converted to NAD phosphate (NADP), which mainly catalyzes anabolic reactions in the body. This means that they build larger compounds from smaller, simpler compounds. One example is synthesizing cholesterol and fatty acids.
What is the RDA for niacin?
The Recommended Dietary Allowance (RDA) for niacin (vitamin B3) is 16 mg for men, 14 mg for women, and 18 mg and 17 mg for pregnant and lactating women, respectively. The RDA for children between nine and thirteen years is 12 mg, 8 mg for children between four and eight years, 6 mg for children between one and three years, 4 mg for infants between seven and twelve months, and 2 mg for infants under six months. Niacin can be passed through breast milk, and it is also supplemented in fortified infant formula.
These values are given by the National Institutes of Health, and the RDA represents the daily intake sufficient to meet the dietary needs of 97-98% of healthy individuals. Three ounces of chicken breast contains 64% of the daily value of niacin, and one cup of cooked brown rice contains 33% of the daily value of niacin.
How much is too much?
The Tolerable Upper Intake Level (UL) for niacin is 35 mg for men and women, 30 mg for adolescents, 20 mg for children between nine and thirteen years, 15 mg for children between four and eight years, and 10 mg for children between one and three years. The UL is not established for infants. The UL represents the maximum daily intake that is unlikely to cause negative health effects.
There is no data on adverse effects of excess niacin obtained from food, as it is very rare. However, some adverse effects can be observed by taking excessively large doses of niacin from dietary supplements.
High doses of nicotinic acid between 30 and 50 mg can cause flushing of the face due to dilation of blood vessels, headache, and decreased blood pressure. These symptoms can be mitigated by taking the supplements with food or starting with a tiny dose and increasing it over time. When extreme doses of nicotinic acid between 1,000 and 3,000 mg daily are taken long term, a variety of adverse effects can occur; it can be damaging to the liver, and it can cause nausea, heartburn, and vision impairments.
What are the benefits of niacin?
Niacin supplementation can be beneficial for reducing the symptoms of cardiovascular disease. High-dose nicotinic acid supplements are often given to help improve blood lipid profiles. Studies show that this treatment can reduce LDL cholesterol, or bad cholesterol, by 10-25% and increase HDL cholesterol, or good cholesterol, by 10-30%. These combined effects could potentially reduce the risk of having a heart attack in those with cardiovascular disease. However, since high-dose nicotinic acid supplements increase the risk of adverse effects, physicians need to determine whether the benefits outweigh the risks.
Some groups have a higher risk of niacin deficiency than others. People who are malnourished due to poverty, eating disorders, alcoholism, or digestive disorders may have an increased risk of niacin deficiency due to not eating enough food. People with low intakes of vitamin B2 (riboflavin), vitamin B6 (pyroxidine), and iron can also be at an increased risk as these nutrients are needed to convert tryptophan to niacin.
Some conditions can also increase the risk of niacin deficiency. Hartnup disease is a rare condition that reduces tryptophan absorption in the small intestine, which means that less tryptophan is converted to niacin in the body. Carcinoid syndrome also decreases tryptophan absorption, increasing the risk of niacin deficiency.
Serious niacin deficiency over prolonged periods of time can result in pellagra. The symptoms of pellagra may include skin discoloration, digestive problems, and damage to the nervous system resulting in depression, fatigue, hallucinations, and memory loss. Pellagra can be fatal if left untreated.
Pellagra can fortunately be corrected with niacin supplementation; the recommended dose is taking a supplement containing 50-100 mg of niacin or niacinamide three times a day for five days. Skin discoloration and neurological symptoms may improve in as little as two days. Pellagra can also be prevented by meeting the RDA for niacin on a daily basis, either through food or niacin supplements.
If you think you have niacin deficiency or are at an increased risk, consider getting your blood levels tested. As always, consult your doctor before you begin taking any vitamin or mineral supplement, to make sure your medications or health conditions don’t make it a serious risk.
MacKay, D., Hathcock, J., & Guarneri, E. (2012). Niacin: Chemical Forms, Bioavailability, and Health Effects. Nutr Rev,70(6), 357-366. doi:10.1111/j.1753-4887.2012.00479.x
Office of Dietary Supplements – Niacin. (2020, June 3). Retrieved July 10, 2020, from https://ods.od.nih.gov/factsheets/Niacin-HealthProfessional/
Pellagra. (n.d.). Retrieved July 10, 2020, from https://www.aocd.org/page/Pellagra