Circulatory and Urinary B-Vitamin Responses to Multivitamin Supplement Ingestion Differ between Older and Younger Adults

Multivitamin and mineral (MVM) supplements are frequently used amongst older populations to improve adequacy of micronutrients, including B-vitamins, but evidence for improved health outcomes are limited and deficiencies remain prevalent. Although this may indicate poor efficacy of supplements, this could also suggest the possibility for altered B-vitamin bioavailability and metabolism in older people. This open-label, single-arm acute parallel study, conducted at the Liggins Institute Clinical Research Unit in Auckland, compared circulatory and urinary B-vitamer responses to MVM supplementation in older (70.1 +/- 2.7 y, n = 10 male, n = 10 female) compared to younger (24.2 +/- 2.8 y, n = 10 male, n = 10 female) participants for 4 h after the ingestion of a single dose of a commercial MVM supplement and standardized breakfast. Older adults had a lower area under the curve (AUC) of postprandial plasma pyridoxine (p = 0.02) and pyridoxal-5 ' phosphate (p = 0.03) forms of vitamin B-6 but greater 4-pyridoxic acid AUC (p = 0.009). Urinary pyridoxine and pyridoxal excretion were higher in younger females than in older females (time x age x sex interaction, p < 0.05). Older adults had a greater AUC increase in plasma thiamine (p = 0.01), riboflavin (p = 0.009), and pantothenic acid (p = 0.027). In older adults, there was decreased plasma responsiveness of the ingested (pyridoxine) and active (pyridoxal-5 ' phosphate) forms of vitamin B-6, which indicated a previously undescribed alteration in either absorption or subsequent metabolic interconversion. While these findings cannot determine whether acute B-6 responsiveness is adequate, this difference may have potential implications for B-6 function in older adults. Although this may imply higher B vitamin substrate requirements for older people, further work is required to understand the implications of postprandial differences in availability.