Niacin

Niacin, also known as nicotinic acid or vitamin B3, is a water-soluble vitamin whose derivatives such as NADH play essential roles in energy metabolism in the living cell. The designation vitamin B3 also includes the amide form, nicotinamide or niacinamide. Severe lack of niacin causes the deficiency disease pellagra, whereas a mild deficiency slows down the metabolism, which in turn decreases cold tolerance and is a potential contributing factor towards obesity.

Nicotinic acid was first discovered from the oxidation of nicotine. When the properties of nicotinic acid were discovered, it was thought prudent to choose a name to dissociate it from nicotine and to avoid the idea that either smoking provided vitamins or that wholesome food contained a poison. The resulting name 'niacin' was derived from nicotinic acid + in.

Nicotinic acid reacts with hemoglobin and myoglobin in meat to form a brightly coloured complex, and thus has been used as a food additive, typically to improve the colour of minced (ground) meat. However, sometimes excess niacin is added to the meat during processing. Though still licensed as a food colouring agent in some countries, it is not licensed as such in Europe.

The body can synthesize niacin from the essential amino acid tryptophan, but the synthesis is extremely slow; 60 mg of tryptophan are required to make one milligram of niacin. For this reason, eating lots of tryptophan is not an adequate substitute for consuming niacin. As serotonin synthesis is reliant on tryptophan availability, inadequate dietary intake of vitamin B3 may also therefore lead to depression.

Because niacin in large quantities is a vasodilator, large doses of niacin (either from vitamin B3 tablets or from treated meats) may cause harmless and short-lived but unpleasant symptoms such as extreme skin flushing resembling a sunburn, itching, gastric disturbances, and lowering of blood pressure. The amide form (strictly speaking a provitamin) does not cause these side effects, but is also not as easily assimilated by the body.

Large doses of niacin are sometimes prescribed to combat high blood pressure, and also to lower blood cholesterol levels. Pharmacologic doses of niacin (1.5 to 6 grams/day) reduces LDL cholesterol levels by 10 to 25 percent and triglyceride levels by 20 to 50 percent. HDL cholesterol levels are also increased by 15 to 35 percent.¹

Vitamin B3 has also been used to treat schizophrenia and other mental illnesses by orthomolecular practitioners. Usually the nicotinamide form is used, as it is considered to be more effective. Unfortunately there is little scientific evidence that this treatment is effective.

Because niacin promotes metabolism, some believe that taking large doses will speed up the elimination of THC from the body and produce a negative result for marijuana on a drug test. There is no evidence that this is effective, and niacin is toxic to the skin and liver in overdose.

Biosynthesis

Food Sources

Animal products:

• liver, heart and kidney
• brewer's yeast
• chicken
• fish: tuna, salmon
• milk
• eggs

Plant Products:

• Seeds:
  • nuts
  • whole grain products
  • legumes
  • saltbush seeds
• Fruits and vegetables:
  • leaf vegetables
  • broccoli
  • tomatoes
  • mushrooms
  • carrots
  • dates
  • sweet potatoes
  • asparagus
  • avocados

References

1. Shepherd J, Packard CJ, Patsch JR, Gotto AM Jr, Taunton OD. Effects of nicotinic acid therapy on plasma high density lipoprotein subfraction distribution and composition and on apolipoprotein A metabolism. J Clin Invest. 1979 May;63(5):858-67. (Full text (http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pubmed&pubmedid=221531))

2. Northwestern University Nutrition: http://www.feinberg.northwestern.edu/nutrition/factsheets/vitamin-b3.htmlda:Niacin de:Nicotinsäure es:Vitamina B3 fa:ویتامین ب٣ fr:Vitamine B3 it:Niacina he:ויטמין B3 lb:Vitamin B3 lt:Niacinas ja:ナイアシン nl:Nicotinezuur pl:Witamina B3 pt:Vitamina PP zh:烟酸