Vitamin B3
Vitamin B3 is a vitamin that includes three forms: nicotinamide, niacin, and nicotinamide riboside. All three forms of vitamin B3 are converted within the body to nicotinamide adenine dinucleotide. NAD is required for human life and people are unable to make it within their bodies without either vitamin B3 or tryptophan. Nicotinamide riboside was identified as a form of vitamin B3 in 2004. The group is also occasionally referred to as the vitamin B3 complex.Mechanism of action
NAD, along with its phosphorylated variant nicotinamide adenine dinucleotide phosphate, are utilized in transfer reactions within DNA repair and calcium mobilization.Toxicity
The daily limit for vitamin B3 has been set at 35 mg. At daily doses of as low as 30 mg, flushing has been reported, always starting in the face and sometimes accompanied by skin dryness, itching, paresthesia, and headache. Liver toxicity is the most serious toxic reaction and it occurs at doses >2 grams/day. Fulminant hepatitis has been reported at doses between 3-9 grams/day with needs for liver transplantation. Other reactions include glucose intolerance, hyperuricemia, macular edema, and macular cysts.Deficiency
can cause pellagra, a disease found in many alcoholics in North America. Symptoms include vomiting, loss of appetite, abdominal pain, and general fatigue.
