A Crossover Study of Noodle Soup Consumption in Melamine Bowls and Total Melamine Excretion in Urine

Abstract

Background Melamine exposure remains common even after the 2008 melamine-tainted baby formula incident. Another source of melamine exposure is melamine tableware. Aims To investigate if consumption of hot noodle soup served in melamine bowls would increase total urinary melamine excretion. Methods In a randomized 2 x 2 crossover study, we asked one group (3 men and 3 women, Group A) to consume 500 mL hot noodle soup (initial temperature: 90oC) served in a melamine bowl as breakfast for 30 min. We collected spot urine sample prior to and in 2 hrs intervals for 12 hrs after consumption. Another group (3 men and 3 women, Group B), following the same procedures, consumed the same soup from ceramic bowls. After a 3-week washout, the assigned treatments were reversed. Urinary melamine levels were measured by LC-MS/MS. Total melamine excretion was calculated as melamine concentration of one-spot urine sample ´ amount of that spot urine and the amounts of all the urine samples collected for 12 hrs after the participant consumed hot noodle soup were summed. A Wilcoxon signed ranks test was calculated to examine the absolute differences of total melamine excretion between two groups. P-values were 2-sided; significance a 0.05 level. Results 12 healthy people (6 men, 6 women; aged 20-27 years) participated. All urine samples from all participants were collected after consumption for 12 hrs in both groups. Total melamine excretion (mean ± SE (standard error)) in urine for 12 hrs was 8.35 ± 1.91 mg and 1.31 ± 0.44 mg in melamine bowls and ceramic bowls, respectively. The difference was highly significant (7.04 ± 1.62 mg; P = 0.0005). Conclusions Melamine tableware may release large amounts of melamine when used to serve high temperature foods. Although the clinical significance of what levels of urinary melamine concentration has not yet been established, the consequences of long-term melamine exposure still should be of concern.