High energy adjusted free glutamate
High energy-adjusted free glutamate intake among adults with high education level (above college) or high poverty income ratio (≥3.50) might be a consequence of the difference in intake of some foods such as vegetables and fruits, reflecting upon their socioeconomic status. Previous studies have shown a positive association between income and vegetable consumption , . For children, energy-adjusted free glutamate intake was not significantly different between poverty income ratio groups. It is possible that Go 6983 sale greater participation in the National School Breakfast and Lunch Programs as well as the Summer Food Service Program among children with lower poverty income ratio attenuates potential differences between demographic groups . The Mexican American group had a relatively higher intake of free glutamate, and mixed dishes-Mexican was the major contributor of free glutamate both among Mexican American children and adults. These results suggest that a specific food intake pattern followed by particular race/ethnicity had a significant effect on the free glutamate food sources, especially among Mexican Americans , . We acknowledge that the present study has several limitations that are worth mentioning. First, caution is needed to address the heterogeneity of the values in the FGDB and unrepresentativeness of foods and beverages in the United States. The FGDB was developed based on published literature, including 172 values obtained from food analyses described by 32 published articles and Ajinomoto Co. Inc. These values were obtained using different analytical methods by researchers in different countries and included some works published decades ago. In addition, analysis of foods and beverages by Ajinomoto Co. Inc. was limited to a collection from specific retail stores located in three areas. Furthermore, some foods and beverages had to be purchased at other stores in the same area. These procedures may have resulted in selection bias. However, we excluded literature and values not satisfying our eligibility criteria to maintain a high quality of the database, and we chose to use median value as a representative value to overcome the issue related to variation in the reported values. In addition, the difference of analytical methods among selected articles was considered as negligible because several studies reported good validation among different methods for amino acid analyses , . Second, there were fewer documents written in English and data sources were limited to websites such as PubMed and Web of Science. However, it is unlikely that literature written in other languages would report the analytical results about food items available in the United States. We conducted a thorough literature search in these data sources, subsequently selecting the target literature by screening each title, abstract, and included content. However, it cannot be completely ruled out that some documents describing free glutamate content of foods or beverages might have been missed in this study. Third, although this study focused on natural free glutamate, some analytical values obtained from published literature might include foods to which MSG was added during food processing. However, the number of processed foods and dishes in the FGBD was relatively small, and free glutamate content values for mixed dishes were assigned the values obtained from the FCID recipe instead of the values of dishes or processed foods in the FGBD. Considering this, the effect of contamination of free glutamate from MSG in FGBD would have minimal impact on our estimates. Fourth, a change of free glutamate content during cooking , ,  was not considered in our study due to the lack of available information. Additionally, previous reports revealed that around 15% of children and 25% of adults under-reported their energy intake during NHANES 2003-2012 , . Although primary food sources of free glutamate were generally low energy-dense foods, it is possible that our results might also present underestimated values. Therefore, our results should be interpreted as an approximate estimation of naturally-occurring free glutamate intake, and more information would be needed to improve FGBD for a better assessment of dietary glutamate intake.