Niacin is a water-soluble nutrient belonging to the B complex family. According to Elson Haas, M.D., author of "Staying Healthy with Nutrition," niacin is converted in your body to its active form, nicotinamide adenine dinucleotide, or NAD. NAD and its relative, NADP, function as coenzymes in the metabolism of energy molecules, including carbohydrates, proteins, fats and alcohol. The May 2009 issue of "Dermatology Online Journal" reports that niacin deficiency in the Western world is mostly confined to poor people or alcoholics.
Functions
NAD serves as an electron transfer vehicle in reactions that break down nutrients to produce energy in your cells. It is intimately involved in the Krebs cycle, an enzymatic pathway used by your mitochondria to produce the high-energy molecule called adenosine triphosphate, or ATP. NADP also carries electrons from one molecule to another, but it is more often involved in synthetic reactions that produce large molecules, such as fatty acids or cholesterol. Niacin supports the health of your skin, digestive tract, blood vessels, brain and reproductive system. Many of niacin's functions are impaired in alcoholics.
Sources and Deficiency
Niacin is found in liver and other organ meats, fish, poultry, dried legumes, peanuts, wheat germ, whole grains, milk and eggs. Some of these foods contain both niacin and the amino acid tryptophan, which can be converted to niacin in your body. Alcoholics tend to eat poorly, which limits their intake of both niacin and tryptophan. Niacin deficiency leads to weakness, fatigue, digestive problems and skin breakdown. Severe niacin deficiency results in a condition called pellagra, which is classically characterized by "four Ds": diarrhea, dementia, dermatitis and -- if untreated -- death.
Deficient Tryptophan Conversion
Pellagra is an occasional complication of alcoholism, but mild-to-moderate niacin deficiency is common among alcoholics. Even if niacin and tryptophan are supplied, alcohol interferes with these nutrients' metabolism. Studies published in the June 1974 and June 1982 issues of "The American Journal of Clinical Nutrition" suggested that alcohol preferentially inhibits enzymes that convert tryptophan to niacin while simultaneously enhancing the activity of enzymes that convert tryptophan to other substances, thereby decreasing tissue niacin levels.
Considerations and Recommendations
Alcoholism usually reduces dietary intake of niacin and its precursor, tryptophan. Furthermore, alcohol interferes with the metabolism of tryptophan and niacin when they are consumed, leading to niacin deficiency in many alcoholics. Recommended dietary allowances for niacin vary from 2 mg daily for infants to 18 mg for pregnant women. Initial treatment of niacin deficiency in alcoholics involves oral supplementation with doses of 100 to 300 mg daily in three or four divided doses. As symptoms resolve, your dosage can be reduced to 50 mg to 100 mg daily. Additional nutritional support is also usually required. Ask your physician if you need additional niacin.
References
- "Staying Healthy with Nutrition: Vitamin B3 (Niacin)"; Elson M. Haas, M.D.; 2006
- "Dermatology Online Journal"; Pellagra Associated with Esophageal Carcinoma and Alcoholism; A. Nogueira, et al.; May 2009
- "The American Journal of Clinical Nutrition"; Relationship of Dietary Tryptophan and Niacin to Tryptophan Metabolism in Alcoholics and Nonalcoholics; I.R. Payne, et al.; June 1974
- "The American Journal of Clinical Nutrition"; Tryptophan Metabolism in Alcoholic Pellagra Patients: Measurements of Urinary Metabolites and Histochemical Studies of Related Muscle Enzymes; H. Vannucchi, et al.; June 1982
