Dietary Sources of Melamine Exposure Among Participants in the National Health and Nutrition Examination Survey (2003-2004)

Background: Melamine is an industrially synthesized commercial chemical present in animal feed, pesticides, and fertilizers. High levels of melamine exposure due to historical food adulteration events have led to acute renal failure. Low level melamine exposure is pervasive in the general population, and chronic low-level exposure may lead to negative health consequences. Melamine has been detected in foods in the US, including meat and dairy products. This study aimed to determine the food sources associated with urinary melamine concentrations and assess how age might modify the relationship between dietary factors and melamine concentrations. Methods: This analysis used nationally representative data from the National Health and Nutrition Examination Survey (NHANES) 2003-2004 including 10 meat and dairy dietary exposures and 20 non-meat or dairy dietary exposures from 24-hour food recalls, and creatinine-adjusted urinary melamine concentration (n=478). Multivariate linear regression was used to examine the relationship between dietary intake and log-transformed creatinine-adjusted melamine while controlling for sex, age, race, body mass index (BMI) status, family poverty income ratio (PIR), and creatinine. Interaction terms were added to fully adjusted models to examine potential effect modification by age. Results: In fully adjusted models, each additional ounce of processed meat consumed was associated with a 9.64% (95% CI: 2.03, 17.71) higher melamine concentration (p<0.05). Each additional ounce of total meat was associated with 3.74% (-7.29, -0.05) lower melamine (p<0.05) and each ounce of red meat was associated with 5.55% (-11.05, 0.21) lower melamine (p=0.06). We also observed several positive associations between other food groups and melamine, including fruit 10.85% (-1.89, 25.24), whole grain 21.05% (9.2, 34.18), and soy 7.47% (-0.4, 16.07) (p<0.10). The relationships between certain dietary exposures (non-whole grains, white potatoes, starchy vegetables, alcohol (p<0.05), and red meat, solid fat (p<0.10)) and melamine were modified by age. Increasing age appeared to reduce the association between these dietary exposures and melamine. Conclusions: This study identified several food groups that are positively and negatively associated with melamine exposure in the US. Results were mixed for meat intake. Positive associations with fruit, whole grains, and soy suggest that the use of pesticides in food production may contribute to melamine exposure. Our results also suggested that younger age groups may have disproportionately higher urinary melamine in association with certain food groups compared with older ages. Further research, including young children, should be conducted to clarify the dietary sources of melamine in the current US food supply and examine their contribution to total melamine exposure and potential adverse health outcomes.