What Is Used For Synthesis Of Niacin? - …
Niacin intakes (expressed in NEs) that would correspond to N1-methyl-nicotinamide excretions of 1.0 mg/day are calculated from the results of four experimental studies in which NEs of 8 to 12 mg/ day were fed (). A study by Patterson and colleagues (1980) was not used because no individual data were provided. In calculating the niacin intakes that would result in the N1-methyl-nicotinamide excretion level of 1 mg/day, a linear relationship was assumed. This approach is conservative; if more niacin was fed, the ratio of niacin to the excretion of N1-methyl-nicotinamide would become somewhat lower. Because all the studies were judged satisfactory in quality, a weighted average of the results was calculated. The overall average intake equivalent to the excretion of 1 mg/day of N1-methyl-nicotinamide is 11.6 ± 3.94 (standard deviation), with a CV of 34 percent.
What Is Used For Synthesis Of Niacin
Data Selection. The data sets used to identify the lowest-observed-adverse-effect level (LOAEL) for niacin included anecdotal reports and clinical trials involving oral intake of niacin by healthy individuals. Studies involving parenteral administration were not considered in the dose-response assessment. Studies involving immediate-release forms of niacin were considered more relevant to niacin intake by the general population than were studies involving sustained-release forms.
Niacin status and dietary requirement can be estimated by using biochemical or clinical endpoints of niacin deficiency. Biochemical changes occur well before the appearance of overt signs of deficiency. Biochemical markers include daily urinary excretion of methylated metabolites, the ratio of 2-pyridone to N1-methyl-nicotinamide in urine, erythrocyte pyridine nucleotides, oral dose uptake tests, erythrocyte nicotinamide adenine dinucleotide (NAD), and plasma 2-pyridone derivative.
Nicotinic Acid (Niacin) for High Cholesterol - WebMD
From , it might be interpreted that women require more niacin per 1,000 kcal than do men. However, the studies are too few and not sufficiently comparable to justify such a conclusion, especially considering a lack of evidence that utilization of niacin is less efficient for women than for men. The studies varied widely in methods, including the types of foods provided, which could have marked effects on the bioavailability of niacin. It is thus assumed that women have a slightly lower requirement than do men because of their size and average energy utilization. Therefore, the EAR is estimated to be 12 mg of NEs for men and 11 mg of NEs for women. Data are not available for determining whether the niacin requirement changes with age in adults.
Niacin is necessary for the synthesis of sex hormones
that is above the minimal excretion at which pellagra symptoms occur. Urinary excretion of N1-methyl-nicotinamide was found to be 1.2 mg/day in men on low but adequate niacin diets that resulted in no signs or symptoms of pellagra (Horwitt et al., 1956; Jacob et al., 1989). Urinary N1-methyl-nicotinamide excretion was found to be 0.6 mg/day in three females on corn-based, niacin-deficient diets that resulted in clinical signs and symptoms of pellagra (Goldsmith et al., 1952, 1955). A urinary excretion value for N1-methyl-nicotinamide of 1.0 mg/day has been chosen as an interpolated level of niacin excretion; it reflects a niacin intake that is above the intake that results in clinical niacin deficiency and thus is minimal or barely adequate.
Niacin is also necessary for the synthesis of fatty acids, ..
(Niacin inhibits hepatocyte diacylglucerol acyltransferase-2, an important enzyme in triglyceride synthesis, making triglycerides less available for uptake into lipoprotein particles and resulting in accelerated degradation of apo B and decreased secretion of VLDL and LDL particles by the liver).
Vitamin B3 / Niacin Side Effects, Benefits & Foods - Dr. …
The best biochemical measure for estimating the average requirement was judged to be niacin metabolite excretion data, namely the metabolites N1-methyl-nicotinamide and its 2-pyridone derivative. These measures have been reported the most extensively. The niacin intakes that result in these measures being above the levels considered barely adequate represent some degree of body pool reserve. Niacin metabolites are not excreted until adequate tryptophan is available to meet needs for the synthesis of protein, nicotinamide adenine dinucleotide, and nicotinamide adenine dinucleotide phosphate (Fu et al., 1989; Vivian et al., 1958). Metabolite excretion measures are more sensitive to niacin depletion than are other biochemical measures, such as blood levels of pyridine nucleotides or tryptophan. Whereas pellagra is prevented with NEs of about 11 mg/day (at 2,500 kcal/day), restoration of niacin metabolite excretion beyond minimal occurs at intakes of NEs of about 12 to 16 mg/ day. Excretion of N1-methyl-nicotinamide rather than the 2-pyridone derivative is preferred as the target measure for estimating the niacin requirement because this metabolite better differentiates marginal from adequate niacin intakes (Jacob et al., 1989), interpretive guidelines exist for this metabolite (ICNND, 1963), and more data are available for this than for other metabolites.