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Tuesday, March 10, 2009

The ABC's of Vitamins - Vitamin B3

Much like vitamin B2, vitamin B3 is not a single substance; the nomenclature covers both niacin and niacinamide. Niacin is the generic name used for nicotinic acid, whereas niacinamide is used for the amide structure (-NH2) nicotinamide.

Nicotinamide is the reactive part of the co-enzymes NAD & NADP. NAD & NADP and their associated co-enzymes are involved in many of the body’s oxidative & reductive reactions (example: lactate to pyruvate to Acetyl-CoA). NAD also plays a role in DNA repair.Vitamin B3 can be made by our bodies from the amino acid tryptophan, but we also get it from chicken, tuna, liver, lean red meats, legumes and peanuts. Like so many of the B vitamins, vitamin B3 is also readily found in many cereal grains. Unfortunately much of it (80-90%) is as bound nicotinic acid, which is not very bioavailable, although treatment with acid or alkali can unbind it and make it more available. And vitamin B3 is completely lost in the milling process, which is why cereal & grain products in the US are fortified; all those wonderful vitamins are stripped away in the processing from whole grain to refined grain.

Normal protein intakes, without any other sources will meet our body’s requirement for this vitamin which means deficiency of vitamin B3 is rare, but among those who are extremely malnourished it can still happen. The symptoms associated with deficiency include dementia, diarrhea, dermatitis and eventually death. Interestingly, pregnancy makes the conversion of tryptophan to niacin twice as efficient and contraceptive pills also increase efficiency too (although not quite as much). Toxicity is rare, but at levels greater than 100mg per day, skin flushing occurs and in even higher doses it can cause gouty arthritis and liver damage.

I’ll be moving on down (or is it up?) the list of the B vitamins, so please come back!

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