Nicotinamide adenine dinucleotide niacin source

Rice bran is the richest natural source of B-complex vitamins. Considerable amounts of thiamin (Bl), riboflavin (B2), niacin (B3), pantothenic acid (B5) and pyridoxin (B6) are available in rice bran (Table 17.1). Thiamin (Bl) is central to carbohydrate metabolism and kreb s cycle function. Niacin (B3) also plays a key role in carbohydrate metabolism for the synthesis of GTF (Glucose Tolerance Factor). As a pre-cursor to NAD (nicotinamide adenine dinucleotide-oxidized form), it is an important metabolite concerned with intracellular energy production. It prevents the depletion of NAD in the pancreatic beta cells. It also promotes healthy cholesterol levels not only by decreasing LDL-C but also by improving HDL-C. It is the safest nutritional approach to normalizing cholesterol levels. Pyridoxine (B6) helps to regulate blood glucose levels, prevents peripheral neuropathy in diabetics and improves the immune function. 

Nicotinamide adenine dinucleotide (NAD+ in its oxidized form) and its close analog nicotinamide adenine dinucleotide phosphate (NADP+) are composed of two nucleotides joined through their phosphate groups by a phosphoanhydride bond (Fig. 13-15a). Because the nicotinamide ring resembles pyridine, these compounds are sometimes called pyridine nucleotides. The vitamin niacin is the source of the nicotinamide moiety in nicotinamide nucleotides. 

Niacin, a water-soluble vitamin vital for oxidation by living cells, functions in the body as a component of two important coenzymes nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP). NAD and NADP are involved in the release of energy from carbohydrate, fat, and protein, and in the synthesis of protein, fat, and pentoses for nucleic acid formation. Milk is a poor source of preformed niacin, containing about 0.08 mg per 100 g. However, milk s niacin value is considerably greater than indicated by its niacin content (Horwitt et al. 1981). Not only is the niacin in milk fully available, but the amino acid tryptophan in milk can be used by the body for the synthesis of niacin. For every 60 mg of tryptophan consumed, the body synthesizes 1 mg of niacin. Therefore, the niacin equivalents in 100 g milk equal 0.856 mg including that from pre-... 

Nicotinamide-adenine dinucleotide (NAD diphosphopyri-dine nucleotide) and nicotinamide-adenine dinucleotide phosphate (NADP also termed triphosphopyridine nucleotide) represent most of the niacin activity found in good sources that include yeast, lean meats, liver, and poultry. Milk, canned salmon, and several leafy green vegetables contribute lesser amounts but are still sufficient to prevent deficiency. Additionally, some plant foodstuffs, especially cereals such as corn and wheat, contain niacin bound to various peptides and sugars in forms nutritionally not readily available (niacinogens or niacytin). Because tryptophan is a precursor of niacin, protein provides a considerable portion of niacin equivalent. As much as two thirds of niacin required by adults can be derived from tryptophan metaboHsm via nicotinic acid ribonucleotide... 

The Federal Enrichment Act of 1942 required the millers of flour to restore iron, niacin, thiamin and riboflavin lost in the milling process. Enriched flours and baked goods made from them are now excellent sources of niacin. Niacin may also be found in meat, poultry, fish, whole grains, and peanut butter. Besides direct niacin intake, humans can convert the amino acid tryptophan to niacin. Many people take daily vitamin supplements to ensure they get enough niacin and other essential nutrients, see also Coenzyme Nicotinamide Adenine Dinucleotide. 

Nicotinic acid (niacin) and various nicotinamides are sources of the coenzyme nicotinamide adenine dinucleotide, synthesized in the mitochondria and vital for oxidative energy production in many metabolic reactions. The RDA is 15-20 mg, normally acquired from a balanced diet of meat, fish, whole cereals and yeast. Peas, beans, nuts, fruit and vegetables are all good sources of this vitamin. 

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