Get to Know Vitamin B3

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Get to Know Vitamin B3

Vitamin B3 is part of the B vitamin family. Like its other B vitamin cousins, it helps the body turn food into energy. It plays other roles in the body, as well. Read on to learn more.

What is vitamin B3?

Vitamin B3 is a water-soluble vitamin that also goes by the names “niacin” and “nicotinic acid.” Niacin is also available as a prescription medication (Niaspan or Niacor) to help lower cholesterol levels.

What does vitamin B3 do?

The tissues in the body convert niacin into a metabolically active form, which is a coenzyme called nicotinamide adenine dinucleotide (NAD), according to the Office of Dietary Supplements (ODS), which is part of the National Institutes of Health (NIH). More than 400 enzymes in the body need NAD to carry out various reactions. NAD is also converted into another active form, a coenzyme called nicotinamide adenine dinucleotide phosphate (NADP), which is found in all body tissues except skeletal muscle.

Long story short, NAD helps to transfer the energy in carbohydrate, protein, and fat into something called ATP, which is the primary fuel source for cells. NADP plays a role in helping make cholesterol and fatty acids in the body.

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Other functions of vitamin B3 include:

  • Helping to make sex hormones and stress hormones in the adrenal glands and other parts of the body
  • Supporting circulation
  • Suppressing inflammation

Very high doses (more than 100 times the Recommended Dietary Allowance, or RDA) of nicotinic acid, a form of vitamin B3, taken regularly over time are used to treat a cholesterol issue called dyslipidemia. Dyslipidemia means that levels of blood lipids (fats) are too high or too low. Nicotinic acid may be prescribed to help increase HDL, or “good,” cholesterol levels, along with lowering LDL (“bad”) cholesterol and triglycerides, a type of blood fat. However, nicotinic acid has not been shown in research to lower the risk of having a heart attack, stroke, or sudden cardiac death. People who take a statin, a type of medicine commonly prescribed to help lower cholesterol levels, should not take nicotinic acid.

What foods have vitamin B3?

Vitamin B3 is found in a variety of both plant and animal foods. Top food sources of this vitamin are:

  • Beef liver
  • Beef and pork
  • Chicken and turkey breast
  • Fish
  • Eggs
  • Milk
  • Rice
  • Legumes, including peanuts
  • Enriched breads and cereals
  • Nuts and seeds
  • Bananas

In addition, vitamin B3 is found in multivitamin-mineral supplements, in supplements that contain other B vitamins, and in supplements that contain only vitamin B3. Nicotinic acid and nicotinamide are the two most common forms of niacin in supplements. The amount of vitamin B3 in supplements can far exceed the RDA, and this can cause skin flushing. For this reason, some supplements may contain an extended or time-released form to limit flushing from occurring. A formulation that contains vitamin B3 in the form of inositol hexanicotinate may be labeled as “flush free” but the absorption of the vitamin is about 30% lower than from nicotinic acid or nicotinamide, says the ODS.

How much vitamin B3 do you need?

Vitamin B3 is measured in milligrams (mg) of niacin equivalents (NE). This measurement is used because the body can make vitamin B3 from tryptophan, an amino acid. The mg NE takes into account vitamin B3 from food as well as what the body makes from tryptophan.

The Recommended Daily Allowance for vitamin B3 is as follows:

  • For men age 19 and older: 16 mg NE daily
  • For women age 19 and older: 14 mg NE daily
  • For pregnancy: 18 mg NE daily
  • For lactation: 17 mg NE daily

What are signs of vitamin B3 deficiency?

Vitamin B3 is rare in the United States, as most people consume more than the RDA. The 2015-2016 National Health and Nutrition Examination Survey (NHANES) found that the average vitamin B3 intake from foods was 31.4 mg in men and 21.3 mg in women.

A severe vitamin B3 deficiency can cause pellagra (which is uncommon in industrialized countries). Symptoms of pellagra include:

  • Rough skin that turns red or brown in the sun
  • A bright red tongue
  • Vomiting, constipation, or diarrhea
  • Depression
  • Headaches
  • Extreme tiredness
  • Hallucinations
  • Memory loss
  • Loss of appetite

Pellagra can lead to death if not treated. This disease is treated with high doses of vitamin B3, along with a balanced diet.

Groups of people who are at risk of a vitamin B3 deficiency are:

  • People who eat a very limited diet, in terms of variety and quantity
  • People with alcoholism
  • People with anorexia
  • People with gastrointestinal disorders
  • People who have had weight-loss surgery
  • People with carcinoid syndrome, a type of slow-growing cancer in the digestive tract
  • People with Hartnup disease, a rare genetic disorder
  • People who don’t consume enough vitamin B2, vitamin B6, or iron

What are signs of vitamin B3 toxicity?

There are no known toxic effects of getting too much vitamin B3 from food sources, since this vitamin is water-soluble and excess amounts are excreted in the urine.

However, high intakes (1,000 to 3,000 mg daily) of nicotinic acid and nicotinamide taken as a dietary supplement or as a medication can cause unpleasant or harmful side effects, such as:

  • Skin flushing, which may be accompanied by burning, tingling and itching
  • Low blood pressure
  • Rapid heartbeat
  • Stomach pain
  • Gout
  • Blurry vision

Impaired glucose tolerance and insulin resistance are other possible side effects of high doses vitamin B3; these conditions can cause type 2 diabetes. Higher doses of niacin can lead to liver damage.

The Mayo Clinic advises that people who have liver disease, peptic ulcer disease, or who have severe low blood pressure avoid taking large doses of vitamin B3. In addition, pregnant women should avoid taking prescription niacin for high cholesterol (niacin used to treat a deficiency is safe during pregnancy when taken in recommended amounts).

Other things to know about vitamin B3

Niacin supplements can interact with some substances, including:

  • Alcohol
  • Allopurinol, for gout
  • Blood-thinner drugs and herbal supplements
  • Blood pressure drugs and herbal supplements
  • Zinc
  • Chromium
  • Some diabetes medications
  • Statins

Since many people who have diabetes may be taking diabetes medication, a statin, or chromium, be sure to discuss the use of a niacin supplement with your health care provider. Also, avoid taking high doses of vitamin B3 on your own without first talking with your health care provider.

If your health care provider has prescribed a niacin for you, discuss the best time to take this medicine. It’s generally recommended to take the immediate-release form of niacin after your evening meal, and the extended-release form at bedtime after you’ve eaten a low-fat snack rather than in the morning or on an empty stomach, since doing so could lead to skin flushing or an upset stomach, advises the website GoodRx.

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Amy Campbell, MS, RD, LDN, CDCES

Amy Campbell, MS, RD, LDN, CDCES

Amy Campbell, MS, RD, LDN, CDCES on social media

A Registered Dietitian and Certified Diabetes Educator at Good Measures, LLC, where she is a CDE manager for a virtual diabetes program. Campbell is the author of Staying Healthy with Diabetes: Nutrition & Meal Planning, a co-author of 16 Myths of a Diabetic Diet, and has written for  publications including Diabetes Self-Management, Diabetes Spectrum, Clinical Diabetes, the Diabetes Research & Wellness Foundation’s newsletter,, and

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