Vitamin B-3 deficiency can disrupt dozens of processes in the body and can lead to a disease called pellagra.

Vitamin B-3, also known as niacin, plays a key role in skin, digestive, and mental health, and supports the functions of more than 200 enzymes in the body.

Vitamin B-3 is a combination of two chemicals: nicotinic acid and nicotinamide. The body breaks these chemicals down to produce two additional chemicals: NAD and NADP.

NAD and NADP play a role in a variety of chemical reactions inside the body and also support cell metabolism. So, people who don't get enough vitamin B-3 can experience a range of health problems and symptoms, ranging from minor to life-threatening.

Fast facts on vitamin B-3:

  • Vitamin B-3 is a water-soluble vitamin, which means that the body can't store it.
  • The body also cannot make vitamin B-3.
  • Meats and meat alternatives, such as soy, are the richest sources of vitamin B-3.
  • People with vitamin B-3 deficiency typically need vitamin B-3 supplements.

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Oatmeal, bran cereal, soya milk, and wheat germ cereal are high in vitamin B-3.

The recommended daily intake varies according to age, sex, health goals, or a history of vitamin B deficiency. Vitamin B-3 intake is measured in niacin equivalents (NE).

For most people, the following daily intake guidelines will prevent niacin deficiency:

  • infants 0-6 months: 2 NE
  • infants 7-12 months: 4 NE
  • children 1-3 years: 6 NE
  • children 4-8 years: 8 NE
  • children 9-13 years: 12 NE
  • children 14-18 years: 16 NE for boys; 14 NE for girls
  • adults 19 years and older: 16 NE for men; 14 NE for women
  • pregnant women: 18 NE
  • breast-feeding women: 17 NE

A wide variety of foods are rich in niacin. A few options and their niacin content in NE are as follows:

  • Portobello mushrooms: 6 NE per ½ cup
  • cooked potatoes: 3-4 NE per medium-sized potato
  • 100 percent bran cereal: 3-6 NE per 30-gram serving
  • toasted wheat germ cereal: 4 NE per ¼ cup
  • instant cooked oatmeal: 3-5 NE per ¾ cup
  • cottage cheese: 5-6 NE per cup
  • soya milk: 3 NE per cup
  • liver: 10-17 NE per 2 ½-ounce (oz) serving
  • cooked or canned tuna: 10-20 NE per 2 ½- oz serving
  • soy burgers: 10 NE per 2 ½-oz serving
  • pumpkin seeds: 8 NE per ¼ cup
  • black-eyed peas: 3 NE per ¾ cup

Although the body cannot make vitamin B-3, it can convert an amino acid called tryptophan into vitamin B-3. Tryptophan-rich foods, such as turkey and eggs, also contain lots of vitamin B-3, so including these foods in the diet may also help prevent vitamin B-3 deficiency.

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Red, inflamed, and irritated skin may be a symptom of mild vitamin B-3 deficiency.

Severe vitamin B-3 deficiency causes a condition called pellagra.

Pellagra affects the skin, nervous system, digestive system, and mucous membranes, such as the eyes and nose.

Symptoms of pellagra include:

  • Symmetrical lesions on both sides of the body. The lesions are most visible at pressure points and on areas of the skin exposed to the sun. Some people develop lesions that cover their entire hands or feet.
  • Butterfly-shaped lesions on the face, or a "necklace" of lesions around the neck that develop after spending time in the sun.
  • Pain, swelling, and irritation of the mouth or other mucous membranes, such as the vagina or the urethra. Severe deficiency can cause the tongue to turn red or swell. Some people develop sores under the tongue or on their lips.
  • Pain and burning in the throat, chest, or stomach.
  • Digestive pain, such as swelling, vomiting, nausea, diarrhea, and constipation. Some people develop ulcers in their bowels that cause bloody diarrhea.
  • Changes in personality and mental health, including losing contact with reality (psychosis), confusion, memory problems, depression, and paranoia. Sometimes, these symptoms may be incorrectly diagnosed as mental illness.

Less severe cases of vitamin B-3 deficiency may cause less serious symptoms in the skin, nervous system, digestive system, or mucous membranes. Those symptoms might include:

  • irritated or red skin
  • headaches
  • fatigue
  • unexplained digestive problems
  • mood issues, such as anxiety or depression
  • changes in thinking or the ability to concentrate
  • dizziness
  • poor circulation

Some studies have also linked niacin intake to an increased risk of cancer, especially in women. Changes in niacin intake, whether intake is too much or too little, can affect the way cells grow, fuel themselves, and reproduce. Over time, this can cause cellular changes that lead to cancer.

There are two types of vitamin B-3 deficiency:

Primary vitamin B-3 deficiency

Primary vitamin B-3 deficiency occurs when a person does not eat enough vitamin B-3 or tryptophan. People with access to healthful food who eat a varied diet are not typically at risk of primary vitamin B-3 deficiency.

In regions of the world where maize, sometimes called Indian corn, is a major part of the diet, people may not get enough B-3. This is because the body cannot absorb the B-3 in maize unless it has been treated with alkali.

Tortillas are often treated with alkali, making them a good vitamin B-3 source for people who eat maize-rich diets.

Secondary vitamin B-3 deficiency

Secondary vitamin B-3 deficiency occurs when another condition, such as diarrhea, Hartnup disease, liver disease, or alcoholism, interferes with the body's ability to absorb vitamin B-3.

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Getting vitamin B-3 from a varied diet is considered the ideal option, as supplements may cause side effects.

People who are concerned that they have a minor vitamin B-3 deficiency, but who have no significant symptoms, can try treating the deficiency with dietary changes.

Vitamin B-3 supplements can cause numerous side effects, including

People with kidney disease may accumulate too much niacin. So it's unwise to take vitamin B-3 supplements without a doctor's supervision.

When the deficiency is severe enough to cause pellagra, it is not enough to just eat more vitamin B-3. Doctors prefer to treat niacin deficiency with nicotinamide supplements.

Although side effects are possible, nicotinamide is less likely to cause itching or burning skin. The ideal dosage is 250-500 milligrams per day.

Anyone who experiences symptoms of vitamin B-3 deficiency should visit their doctor. Blood and urine tests can diagnose vitamin B-3 deficiency.

For people who have telltale symptoms of pellagra, however, a doctor may skip testing and immediately recommend supplements.

When symptoms are less severe or are unclear, a physician may take a detailed medical history. In some cases, the symptoms of vitamin B-3 deficiency can mimic other deficiencies, so clear information about a person's diet and lifestyle can support an accurate diagnosis.

Vitamin B-3 deficiency is highly treatable with prompt medical attention. It is not, however, something to manage at home.

Many people with vitamin B-3 deficiency have other deficiencies, too. This can be because of a poor diet or difficulty absorbing vitamins. Someone who has a vitamin B-3 deficiency may need further testing to assess whether they also lack other vital vitamins or nutrients.

Some people may need to make significant dietary and lifestyle changes.