(01-03-12) Determinants of urinary methylmalonic acid concentration in an elderly population in the United Kingdom1,2,3

1. Janet E Flatley,
2. Clare M Garner,
3. Maha Al-Turki,
4. Nigel J Manning,
5. Simon E Olpin,
6. Margo E Barker, and
7. Hilary J Powers
+Author Affiliations
1. 1From the Human Nutrition Unit, Faculty of Medicine, Dentistry and Health, University of Sheffield, Sheffield, United Kingdom (JEF, CMG, MA-T, MEB, and HJP), and the Department of Clinical Chemistry, Sheffield Children's Hospital National Health Service Trust, Sheffield, United Kingdom (NJM and SEO).
+Author Notes
?? ↵2 Supported by the UK Department of Health (study code NO5R0014).
?? ↵3 Address correspondence to HJ Powers, Human Nutrition Unit, Faculty of Medicine, Dentistry and Health, University of Sheffield, Sheffield S102RX, United Kingdom. E-mail: [email protected].
Abstract
Background: An age-related deterioration of vitamin B-12 status has been well documented. The early detection of deficiency may prevent the development of serious clinical symptoms, but plasma vitamin B-12 concentration is known to be an imperfect measure of vitamin B-12 status. Urinary methylmalonic acid (MMA) may be a more informative biomarker of vitamin B-12 status; however, biochemical, dietary, and other lifestyle determinants are not known.
Objective: We identified determinants of urinary MMA concentrations in free-living men and women aged ??65 y in the United Kingdom.
Design: A cross-sectional study in 591 men and women aged 65?C85 y, with no clinical evidence of vitamin B-12 deficiency, was conducted to determine the demographic, clinical, and lifestyle determinants of urinary MMA concentration expressed as the ratio of micromoles of MMA to millimoles of creatinine (uMMA ratio).
Results: Twenty percent of subjects had plasma vitamin B-12 concentrations <200 pmol/L. Seventeen percent of the variation in the uMMA ratio could be explained by plasma holotranscobalamin and sex; total vitamin B-12 intake and measures of renal function and gastric function made only a small contribution to the model. The uMMA ratio was lower in people with moderately impaired renal function.
Conclusions: Plasma holotranscobalamin and sex were the most important determinants of uMMA ratio in elderly people with no clinical diagnosis of renal impairment. This biomarker might underestimate vitamin B-12 deficiency in a population in which renal impairment is prevalent. This trial was registered at www.controlled-trials.com as ISRCJN83921062.

Source: Am J Clin Nutr March 2012 vol. 95 no. 3 686-693

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