Variability in the trans fatty acid content of foods within a food category: Implications for estimation of dietary trans fatty acid intakes

Objective: Currently, the published information on trans fatty acid composi tion of foods is incomplete and of questionable accuracy. Detailed fatty ac id analysis of over 200 foods was undertaken for the purpose of determining the variability in trans fatty acid content among foods within a product c ategory, and the significance of this variability to the estimation of tran s fatty acids intakes from analysis of dietary intake data. Methods: The analysis of food fatty acids used gas-liquid chromatography wi th 100 m capillary columns and standardized methodologies for food sampling , fat extraction, separation and quantification of trans fatty acid isomers . For the purposes of this report, trans refers to all non-naturally occurr ing isomers including trans, cis-trans, geometric and positional isomers. Results: The results show that the amount of trans fatty acids varies consi derably among foods within a category, reflecting differences in the fats a nd oils used in the manufacturing or preparation process. For example, the range of trans fatty acids in 17 brands of crackers was 23 to 51% total fat ty acids, representing differences of from 1 to 13 g trans fatty acids per 100 g cracker. The large errors that may arise in estimates of the trans fa tty acid intake of an individual are illustrated by analyses of the potenti al trans fatty acid intake in a sample diet, for each food as calculated us ing the minimum and maximum values for trans fatty acids within a given cat egory. The results of these analyses show estimates of trans fatty acid int ake from a low of 1.4 to 25.4 g a day for the same diet. Conclusion: This study shows that the wide variability in trans fatty acid content of different foods may result in large errors in the estimation of trans fatty acid intake of individuals and, potentially, groups.