Niacin (Vitamin B3)

Niacin, also known as vitamin B3, is the only B vitamin your body can produce from another nutrient — the amino acid tryptophan.

Types

Niacin is a group of related nutrients. The most common forms are:

Nicotinic acid: The most common form in supplements. Also found in both plant- and animal-sourced foods. High-dose nicotinic acid supplements may cause a condition called niacin flush.

Nicotinamide (niacinamide): Found in supplements and foods.

The compound nicotinamide riboside also has vitamin B3 activity. It is found in trace amounts in whey protein and baker’s yeast.

Role and Function

• All dietary forms of niacin are eventually converted into nicotinamide adenine dinucleotide (NAD+) or nicotinamide adenine dinucleotide phosphate (NADP+), which act as coenzymes.
• Like the other B vitamins, it functions as a coenzyme in the body, playing an essential role in cellular function and acting as an antioxidant.
• One of its most important roles is to drive a metabolic process known as glycolysis, the extraction of energy from glucose (sugar).

Dietary Sources

• Niacin is found in both plants and animals. The chart below shows the niacin content of a few of its best sources.
• Yeast extract spread is exceptionally rich in niacin, providing around 128 mg in every 100 grams.
• Other good sources include fish, chicken, eggs, dairy products and mushrooms. Niacin is also added to breakfast cereals and flour.
• Additionally, your body can synthesize niacin from the amino acid tryptophan. Scientists have estimated that 60 mg of tryptophan can be used to create 1 mg of niacin.

Recommended Intake

The table below shows the RDA or adequate intake for niacin. These values are the estimated amount of niacin that most people (97.5%) need to get from their diets every day.

It also shows the tolerable upper intake limit (UL), which is the highest daily intake considered safe for most people.

RDA (mg/day)      UL (mg/day)

Infants        0–6 months           2*                         –

7–12 months        4*                         –

Children      1–3 years              6                           10

4–8 years              8                           15

9–13 years            12                         20

Women       14+ years              14                         30

Men             14+ years              16                         30

Pregnancy                               18                         30–35

Lactation                                 17                         30–35

*Adequate intake

Deficiency

• Niacin deficiency, known as pellagra, is uncommon in developed countries.
• The main symptoms of pellagra include inflamed skin, mouth sores, diarrhea, insomnia and dementia. Like all deficiency diseases, it is fatal without treatment.
• Fortunately, you can easily get all the niacin you need from a varied diet.
• Deficiency is much more common in developing countries where people commonly follow diets that lack diversity.
• Cereal grains are especially low in available niacin, since most of it is bound to fiber in the form of niacytin.
• However, your body can synthesize it from the amino acid tryptophan. As a result, severe niacin deficiency can often be avoided on a high-protein diet.

Side Effects and Toxicity

• Naturally occurring niacin from food does not appear to have any adverse effects.
• However, high supplemental doses of niacin may cause niacin flush, nausea, vomiting, stomach irritation and liver damage.
• Niacin flush is a side effect of immediate-release nicotinic acid supplements. It is characterized by a flush in the face, neck, arms and chest.
• Liver damage is associated with the long-term use of very high doses (3–9 grams per day) of sustained-release or slow-release nicotinic acid.
• Additionally, taking niacin supplements for a long time may increase insulin resistance and raise blood sugar levels.
• Nicotinic acid may also increase the circulating levels of uric acid, worsening symptoms in people who are predisposed to gout.

Benefits of Supplements

• Nicotinic acid supplements at doses ranging from 1,300–2,000 mg per day are commonly used to normalize blood lipid levels.
• They bring down high levels of “bad” low-density-lipoprotein (LDL) cholesterol, while raising levels of “good” high-density-lipoprotein (HDL) cholesterol when they are low. Triglyceride levels may also drop in those taking supplements.
• Some studies also suggest nicotinic acid reduces heart disease risk, but its benefits are controversial and study results have been inconsistent.
• Preliminary evidence also indicates that niacin supplements may improve cognition, but further studies are needed before strong claims can be made.

Summary of Niacin

• Niacin, also known as vitamin B3, is a group of two related compounds — niacinamide and nicotinic acid. They serve many vital functions in the body.
• Niacin is found in many different foods, such as liver, fish, poultry, eggs, dairy products, sunflower seeds and peanuts, to name few. Additionally, it is commonly added to processed food like flour and breakfast cereals.
• Deficiency is rare in Western nations. People who eat low-protein diets that lack diversity are at an increased risk.
• High-dose nicotinic acid supplements are commonly used to normalize blood lipid levels, although some scientists doubt the vitamin’s benefits for heart health.
• But supplements may also have some negative side effects, such as liver damage, reduced insulin sensitivity and niacin flush.