Values for evaluating the nutritional status of water-soluble vitamins in humans

Abstract

Previously, we clarified that the amount of urinary excretion of water-soluble vitamins closely reflects the surplus amount of water-soluble vitamins in the body stores of rats and humans. We tried to set a tentative amount of urinary excretion of eight water-soluble vitamins of nine water-soluble vitamins (except vitamin B 12 ) for maintaining health based on experiments in healthy young females administered a semi-chemically defined diet according to Japanese Dietary Reference Intakes and related data. We proposed a tentative value for the amount of urinary excretion of water-soluble vitamins for maintaining health. The values were: 200–2000 nmol/d for vitamin B 1 ; 200–2000 nmol/d for vitamin B 2 ; 2–15 µ mol/d for 4-pyridoxic acid (a catabolite of vitamin B 6 ); 50–300 µ mol/d for the sum of the nicotinamide catabolites N 1 -methylnicotinamide, N 1 -methyl-2-pyridone-5-carboxamide, and N 1 -methyl-4-pyridone-3-carboxamide; 10–30 µ mol/d for pantothenic acid; 15–100 nmol/d for folate; 50–200 nmol/d for biotin; and 100–2000 µ mol/d for vitamin C. By using these values, we attempted to evaluate the nutritional status of water-soluble vitamins for 709 young Japanese females. The percentage within the tentative value of urinary excretion of water-soluble vitamin for maintaining health was 73.6% for vitamin B 1 , 63.5% for vitamin B 2 , 90.0% for vitamin B 6 , 85.6% for niacin, 58.1% for folate, 85.6% for pantothenic acid, 70.2% for biotin, and 65.4% for vitamin C. The percentage beyond the lower limit of detection was 22.4% for vitamin B 1 , 31.3% for vitamin B 2 , 6.2% for vitamin B 6 , 14.0% for niacin, 40.9% for folate, 12.4% for pantothenic acid, 26.2% for biotin, and 33.0% for vitamin C. The percentage over the upper limit of detection was 4.1% for vitamin B 1 , 5.2% for vitamin B 2 , 3.8% for vitamin B 6 , 0.4% for niacin, 1.0% for folate, 2.0% for pantothenic acid, 3.6% for biotin, and 1.6% for vitamin C. Nutritional assessment using urinary excretion amounts of water-soluble vitamins is persuasive, and leads to the transformation of habitual dietary intakes.