Niacin (B3)

What is vitamin B3?

Vitamin B3, or niacin, is essential for overall health and wellbeing. Niacin is a general term that includes nicotinic acid and niacinamide, which are vitamin B3 molecules that differ in their structure but function similarly in the body.¹ Niacin is a water-soluble vitamin, which means it is not stored in the body in large amounts. Since we cannot produce niacin in sufficient quantities, we must get this vitamin through food or supplements.

Why we need it

Nicotinic acid and niacinamide are precursors to nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP). NAD and NADP are coenzymes (substances required by enzymes to carry out reactions) for over 400 reactions in the body.¹ For example, NAD and NADP participate in reactions that produce energy from nutrients like sugar (through a process called the electron transport chain) or fat (through a process called beta oxidation).¹ In this way, niacin helps our bodies generate energy from the food we eat.

Additionally, niacin supports enzymes involved in gene expression and DNA synthesis and repair. These processes allow our cells to carry out their normal functions and fight off diseases associated with DNA damage.

Niacin also acts as an antioxidant, or a substance that defends the body against oxidative stress (a phenomenon that can contribute to aging and chronic disease). For instance, niacin helps restore levels of antioxidant proteins like glutathione and thioredoxin.¹

Where it’s found

Niacin is found in a variety of foods, mainly meat, fish, and fortified or enriched grains. Examples of niacin-rich foods include:²

Tuna
Salmon
Chicken
Beef
Breads and cereals
Lentils

Niacin is also available in supplement form, either alone or as part of a multivitamin or B-complex supplement.

Our bodies can also produce niacin from the amino acid tryptophan. Foods that are rich in tryptophan include milk, cheese, poultry, nuts and seeds, oats, and beans.² Eating both niacin- and tryptophan-rich foods is important for maintaining healthy niacin levels.³

Daily requirements

The Recommended Dietary Allowance (RDA) for niacin (i.e. the amount that is likely to meet the needs of most healthy people) is 16 milligrams (mg) per day for male adults (over the age of 19), and 1.1 mg per day for female adults.⁴ For women who are pregnant or breastfeeding, the RDA increases to 18 mg per day and 17 mg per day, respectively.⁴

Niacin deficiency

Severe niacin deficiency can cause a disease known as pellagra. There are four main signs of pellagra (the “four Ds”) – diarrhea, dermatitis, dementia, and death.¹ Pellagra can affect digestion (causing diarrhea); it can cause the skin to develop blisters, lesions, and hyperpigmentation (characterizing dermatitis); and it may lead to cognitive decline (causing dementia). If left untreated, pellagra may progress to death.

Most people get enough niacin through foods, so deficiency is relatively rare. However, deficiency is still seen in certain populations. For instance, people who do not eat enough niacin-rich foods, people with alcoholism, and people with malabsorptive conditions like diarrhea may be at higher risk for niacin deficiency.¹

Can you get too much niacin?

Niacin can be harmful if consumed in excessive amounts. Niacin toxicity is typically caused by taking large doses of supplements containing nicotinic acid (rather than from eating niacin-rich foods).1 The most common symptom of niacin toxicity is flushing of the skin, which can be seen with niacin doses as low as 30 mg per day.⁵ Other symptoms of niacin toxicity include light-headedness, itching, nausea, vomiting, headache, and stomach pain.4 Niacin toxicity may also cause more serious conditions such as liver damage, also this generally occurs only after consuming extremely high doses (around 3000 mg per day).⁵

To prevent toxicity symptoms, a Tolerable Upper Intake Level (UL) has been established for niacin. The UL for niacin, or the maximum amount that is likely to be safe, is 35 mg per day for adults (male and female).⁴

Fun facts

Niacin may help lower levels of “bad” cholesterol (LDL cholesterol) and raise levels of “good” cholesterol (HDL cholesterol).1 For this reason, niacin is commonly prescribed as a drug treatment for high cholesterol. Niacin may improve cholesterol levels in various ways, such as by inhibiting enzymes involved in LDL production and HDL breakdown.⁶

Coffee beans contain a compound called trigonelline, which contributes to the signature flavor of coffee. When coffee beans are roasted, trigonelline can be converted to niacin. Because of this, the niacin content may be higher in heavily roasted coffee compared to lighter roasted coffee.⁷