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Niacin deficiency is a consequence of a diet low in both niacin and the amino acid tryptophan, a precursor for the vitamin. Low plasma tryptophan is a non-specific indicator, meaning it can have other causes. The signs and symptoms of niacin deficiency start to revert within days of oral supplementation with large amounts of the vitamin. [23] [24]
Diagnosis is typically made based on clinical suspicion and a low zinc level in the blood. Any level below 70 mcg/dL (normal 70-120 mcg/dL) is considered zinc deficiency. However there is a paucity of adequate zinc biomarkers , and the most widely used indicator, plasma zinc, has poor sensitivity and specificity . [ 53 ]
Independently of clinical symptoms, blood level of tryptophan or urinary metabolites such as 2-pyridone/N-methylnicotinamide ratio <2 or NAD/NADP ratio in red blood cells can diagnose pellagra. The diagnosis is confirmed by rapid improvements in symptoms after doses of nicotinamide (250–500 mg/day) or nicotinamide enriched food. [7]
According to the World Health Organization, an alternative mean of expressing urinary N1-methyl-nicotinamide is as mg/g creatinine in a 24-hour urine collection, with deficient defined as <0.5, low 0.5-1.59, acceptable 1.6-4.29, and high >4.3 [10] Niacin deficiency occurs before the signs and symptoms of pellagra appear. [5]
According to the World Health Organization, an alternative mean of expressing urinary N1-methyl-nicotinamide is as mg/g creatinine in a 24-hour urine collection, with deficient defined as <0.5, low 0.5-1.59, acceptable 1.6-4.29, and high >4.3 [11] Niacin deficiency occurs before the signs and symptoms of pellagra appear. [6]
Liver disease or kidney disease: Niacin can accumulate in people with liver or kidney problems, potentially worsening their condition. [ 1 ] Bleeding disorders : Inositol nicotinate may slow blood clotting, increasing the risk of bleeding for individuals with clotting disorders or those undergoing surgery.
Hartnup disease (also known as "pellagra-like dermatosis" [1] and "Hartnup disorder" [2]) is an autosomal recessive [3] metabolic disorder affecting the absorption of nonpolar amino acids (particularly tryptophan that can be, in turn, converted into serotonin, melatonin, and niacin).
Blood tests are performed to rule out other causes and to confirm an elevated level of vitamin B 6 with an absence of hypophosphatasia. [ 14 ] [ 11 ] [ 12 ] [ 57 ] [ 58 ] Examination does not typically show signs of a motor deficit , dysfunction of the autonomic nervous system or impairment of the central nervous system , [ 4 ] [ 3 ] although ...