Niacin (Vitamin B3)
Niacin (nicotinic acid and nicotinamide) is water-soluble and required to form the coenzymes:
– NAD (nicotinamide adenine dinucleotide)
– NADP (nicotinamide adenine dinucleotide phosphate)
NAD and NADP are required for the proper function of over 200 enzymes in the body, mainly to donate or accept electrons in redox reactions. They are essential for the breakdown of carbohydrates, fats, proteins, and alcohol for energy and in the synthesis of fatty acids and cholesterol.
NAD is also required for the formation of three key enzymes:
– poly-ADP-ribosepolymerase: Involved in cell-signaling and DNA replication, repair and cell differentiation
– ADP-ribosyl cyclase: Involved in cell-signaling through the release of calcium ions.
Niacin can be formed in the body from tryptophan. 60 mg of tryptophan can be converted to 1 mg niacin if there is enough B6 and riboflavin (B2).
There are conflicting results that higher doses (3 grams a day in adults) of nicotinamide can protect the beta cells in the pancreas for new onset diabetics. Large doses (up to 3 grams daily) of nicotinic acid but not nicotinamide, reduce cholesterol and serum Lp(a) lipoprotein, shifting lipoproteins to the larger more beneficial sizes and increasing the protective HDL (high-density lipoproteins).
SYMPTOMS OF DEFICIENCY
Pellagra is the classic disease of niacin deficiency which we learned in medical school as the 4 D’s:
– Dermatitis (thick scaly rash with increased pigment in the sun exposed surfaces)
– Diarrhea (GI symptoms including diarrhea, red tongue, and vomiting)
– Dementia (neurological symptoms include disorientation, memory loss, apathy, depression, headache, and fatigue)
– Death (rare and only in severe untreated cases)
Niacin deficiency is typically only seen where diets are almost exclusively refined corn. Those with Hartnup’s Disease (defective tryptophan absorption) or carcinoid syndrome (increased serotonin and other catecholamines from tumors) and those on prolonged isoniazid (antituberculosis medication) can also develop niacin deficiency.
Whole grains or fortified cereals, fish and meats, legumes including peanuts, seeds, potatoes, yeasts, and nutritional supplements.
SAFETY AND TOXICITY
Nicotinic acid causes skin flushing, itching, and sometimes nausea and vomiting. Elevated liver function, or even hepatitis, has been seen typically at doses above 3 grams a day but as low as 500 mg daily.
Nicotinamide is generally better tolerated with less flushing of the skin, but liver toxicity has been seen with prolonged doses above 3 grams a day.
Tolerable Upper Limits
Infants not established
Children 10 – 20 mg/ day
Teens/Adults 30 mg/day
Use of the high doses mentioned for treating diabetes or high cholesterol, should be supervised by a physician with monitoring of liver functions.
Learn more about Niacin here…