VARIABILITY OF THE METHIONINE LOADING TEST - NO EFFECT OF A LOW-PROTEIN DIET

The methionine loading test is used for the diagnosis of impaired meth ionine/homocysteine metabolism, in particular the transsulfuration pat hway. Usually this test is performed on a low protein diet to control the intake of methionine. However, this is inconvenient and relatively expensive. In this study we compared the effects of a low protein die t and a standard diet on methionine loading test in 28 subjects (cross over design). The mean difference in homocysteine concentration after methionine loading between the two diets was 1.3 [confidence interval (CI) 95%-1.0-3.6] mu mol/L which demonstrates that a special low prote in diet is not essential in the performance of the methionine loading test. We also observed that 3 weeks after the first methionine loading test, fasting serum concentration of folate was higher and vitamin B- 12 concentration was lower.