Vitamin B3, also known as niacin or nicotinamide, is an essential nutrient in the human diet.  Some body niacin can be converted from another dietary nutrient called tryptophan.  Deficiency of niacin in well-nourished children is rare.  The deficiency disease is called pellagra.  The symptoms of mild pellagra are non-specific and include: weakness, burning or tingling sensation of the skin, numbness, decreased appetite, and dizziness.  Severe deficiency of niacin can cause the "three D's" - dermatitis, diarrhea, and dementia.  Niacin in foods does not seem to cause ill effects when taken in excess.  Niacin in a pill form may cause problems when too much is taken, such as: burning, tingling, itching, and redness of the skin.

What is vitamin B3 and where is it found?

Vitamin B3 is an essential vitamin found in foods such as: meat, fish, poultry, fortified grains and cereals.  Eggs and milk are a poor source of vitamin B3, but contain tryptophan, which can be converted to a usable form of niacin in the body.

What are the symptoms of vitamin B3 deficiency and who gets it?

Vitamin B3 deficiency is rare in children.  Malnourished children may be at risk for this and other nutrient deficiencies.  Symptoms of defficiency are non-specific and because this deficiency is often found in combination with other vitamin deficiencies, it is often difficult to determine the true source of the symptoms.

Mild deficiency

• Poor appetite
• Weakness
• Loss of energy
• Burning or numbness of the skin
• Dizziness
• Red, sore tongue
• Cracking of the of the skin/lips at the corners of the mouth

Severe deficiency (pellagra)

• Dermatitis
• Diarrhea
• Dementia

What is pellagra?

Pellagra is the disease caused by inadequate vitamin B3 (niacin) in the body. 

The dermatitis (skin inflammation) is characterized by a dry, red, scaling rash.  The rash is made worse by irritants... including sunlight.  The rash may first appear as diffuse redness (like sunburn).  The hands, feet, and neck are common locations for pellagra-related rash.

Diarrhea associated with pellagra may be mild, severe or even absent.

Dementia associated with pellagra causes may be mild or severe.  Other nervous system symptoms include depression, disorientation, insomnia (difficulty sleeping), and irritability.

How is vitamin B3 (niacin) deficiency diagnosed?

• The key clinical features may suggest the diagnosis.
• A urine test may be helpful.
• Rapid resolution of symptoms with niacin supplementation is likely the best way to diagnose the deficiency.

Can too much vitamin B3 be dangerous?

Yes.  Niacin found in foods is unlikely to cause a vitamin B3 overdose.  Excess niacin is removed from the body in the urine.  Excess amounts of niacin in the pill form may cause flushing or abnormal sensation in the skin.  Very large doses may cause diarrhea and liver damage.

Photo credits - 1. Ragesoss WikiMedia Commons. 2008. 2. Images of Memorable Cases - 50 years at the bedside. Herbert L. Fred, MD, Hendrik A. van Dijk.  Accessed Wikimedia Commons June 2010.

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