Original Communication
European Journal of Clinical Nutrition (2005) 59, 768–775. doi:10.1038/sj.ejcn.1602138 Published online 4 May 2005
Effect of L-methionine supplementation on plasma homocysteine and other free amino acids: a placebo-controlled double-blind cross-over study
Guarantor: G Jahreis.
Contributors: BD: conception, design, conduct of the study, analysis, statistics, data interpretation, writing the manuscript; RF: conception, design, medical attendance; MB: analysis, data interpretation; RS: analysis, data interpretation, statistics; JG: medical attendance; GJ: conception, design, data interpretation.
B Ditscheid1, R Fünfstück2, M Busch2, R Schubert1, J Gerth2 and G Jahreis1
- 1Department of Nutritional Physiology, Institute of Nutrition, Friedrich Schiller University of Jena, Jena, Germany
- 2Department of Internal Medicine III, Friedrich Schiller University of Jena, Jena, Germany
Correspondence: G Jahreis, Department of Nutritional Physiology, Institute of Nutrition, Friedrich Schiller University of Jena, Dornburger Str. 24, D-07743 Jena, Germany. E-mail: Gerhard.Jahreis@uni-jena.de
Received 4 August 2004; Revised 25 October 2004; Accepted 31 January 2005; Published online 4 May 2005.
Abstract
Objective:
The essential amino acid L-methionine is a potential compound in the prophylaxis of recurrent or relapsing urinary tract infection due to acidification of urine. As an intermediate of L-methionine metabolism, homocysteine is formed. The objective was to study the metabolism of L-methionine and homocysteine, and to assess whether there are differences between patients with chronic urinary tract infection and healthy control subjects.
Design:
A randomized placebo-controlled double-blind intervention study with cross-over design.
Setting:
Department of Nutritional Physiology, Institute of Nutrition in cooperation with the Department of Internal Medicine III, Friedrich Schiller University of Jena, Germany.
Subjects:
Eight female patients with chronic urinary tract infection and 12 healthy women (controls).
Interventions:
After a methionine-loading test, the volunteers received 500 mg L-methionine or a placebo three times daily for 4 weeks.
Main outcome measures:
Serum and urinary concentrations of methionine, homocysteine, cystathionine, cystine, serine, glycine and serum concentrations of vitamin B12, B6 and the state of folate.
Results:
Homocysteine plasma concentrations increased from 9.4
2.7 
mol/l (patients) and 8.91.8 mol/l (controls) in the placebo period to 11.24.1 mol/l (P=0.031) and 11.02.3 mol/l (P=0.000), respectively, during L-methionine supplementation. There were significant increases in serum methionine (53.622.0 mol/l; P=0.003; n=20) and cystathionine (0.620.30 mol/l; P=0.000; n=20) concentrations compared with the placebo period (33.012.0 and 0.300.10 mol/l; n=20). Simultaneously, renal excretion of methionine and homocysteine was significantly higher during L-methionine intake.
Conclusions:
Despite an adequate vitamin status, the supplementation of 1500 mg of L-methionine daily significantly increases homocysteine plasma concentrations by an average of 2.0 mol/l in patients and in control subjects. An optimal vitamin supplementation, especially with folate, might prevent such an increase.
Keywords:
L-methionine, homocysteine, serum amino acids, methionine-loading test
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