1284 Am J Clin Nutr 1988;48: 1284-90. Printed in USA. © 1988 American Society for Clinical Nutrition Effect of age on changes in plasma, erythrocyte, and urinary B-6 vitamers after an oral vitamin B-6 load13 Ashima K Kant, PhD; Phylis B Moser- Veillon, PhD; and Robert D Reynolds, PhD ABSTRACF We investigated the effect ofage on indices ofvitamin B-6 metabolism in 36 fasting males aged 25-35, 45-55, and 65-75 y who ingested 17. 15 imol vitamin B-6. There were no significant differences among groups in dietary vitamin B-6 intake, base-line erythro- cyte pyridoxal 5’-phosphate (PLP), and total vitamin B-6 concentrations, and 24-h and base- line urinary excretion oftotal vitamin B-6 and 4-pyridoxic acid (4-PA). Base-line plasma PLP and total vitamin B-6 were higher (p < 0.05) in the youngest group. Increased serum alkaline phosphatase (AP) and decreased dietary vitamin B-6 intake were correlated with decreased base-line plasma PLP and total vitamin B-6. Changes in plasma and erythrocyte PLP concen- trations and excretion of4-PA and total vitamin B-6 postboad were not different among groups. Indices of vitamin B-6 absorption, phosphorybation, and excretion were not affected by age. Am J Clin Nutr 1 988;48: 1284-90. KEY WORDS Vitamin B-6, pyridoxal 5’-phosphate, 4-pyridoxic acid, age, aging, absorp- tion, erythrocytes Introduction Numerous investigators have suggested that there is a high incidence ofmarginal vitamin B-6 nutritional status in elderly people as measured by dietary intake (1-9) and biochemical indices (1, 3, 4, 9-17). A variety of biochem- ical indices of vitamin B-6 nutritional status, namely plasma pyridoxal 5’-phosphate (PLP) (4, 10-12, 18), plasma total vitamin B-6 (16-18), and crythrocyte and serum aminotransferases, were depressed (1-4, 9-11, 1 3-1 7) and urinary xanthurenic acid excretion was in- creased after a tryptophan load (9, 10) in the aged. Some reports (4, 10, 18) suggested that age differences in di- etary vitamin B-6 intake may not be the sole cause for the biochemical changes discussed above and that other age-related mechanisms, including impaired absorption, phosphorybation, and/or increased urinary excretion, may be involved. The purpose ofthis study was to inves- tigate the effect of age on indices of vitamin B-6 absorp- tion, phosphorylation, and excretion as determined by changes in plasma, erythrocytc, and urinary B-6 vita- mers after the ingestion ofa small vitamin B-6 load. Subjects and methods Subjects Thirty-six free-living, apparently healthy male volunteers in the age groups 25-35, 45-55, and 65-75 y (n = 12 per group) were recruited. Informed written consent was obtained from all volunteers. All the procedures followed were approved by the Institutional Review Board for review ofresearch using hu- man subjects ofthe University ofMaryland, College Park. Individuals reporting the presence of liver disease, tubercu- bosis, ceiac disease, kidney disease, or diabetes or a history of gastrointestinal surgery were excluded from the study. None of the subjects was using drugs that are known to affect vitamin B-6 metabolism. Individuals with liver function tests (serum alanine aminotransferase [ALT], aspartate aminotransferase [AST], and albumin) above the normal range or with glucose or protein in the urine were also excluded from the study. All subjects were instructed to discontinue any vitamin-mineral supplement use at least 4 wk before the study. Characteristics of the subjects and the selected biochemical profile are pre- sented in Table I. Experimental procedures All subjects were instructed to keep a record of their usual daily food intake for 3 d preceding the study day. A uniform set of oral and written instructions and forms for recording food intake were provided to each subject. A 24-h urine collec- 1 From the Department ofFood, Nutrition and Institution Admims- tration, University of Maryland, College Park and the Human Nutri- tion Research Center, United States Department ofAgriculture, Belts- ville, MD. 2 Supported in part by grant 1 R03 AG528 1-01 from the National Institute on Aging. 3 Address reprint requests to P Moser-Veillon, Department FNIA, University ofMaryland, College Park, MD 20742. Received September 23, 1987. Accepted for publication December 1, 1987. by guest on July 10, 2011 www.ajcn.org Downloaded from