What are the trans fatty acids issues in foods after discontinuation of industrially produced trans fats? Ruminant products, vegetable oils, and synthetic supplements

Adverse health effect of trans fatty acids (TFAs) are well recognized, which has precipitated efforts to reduce their content in food products. With the decline of dietary TFAs derived from partial oil hydrogenation, interest is focused on the remaining sources of dietary TFAs derived from ruminants (rTFA), deodorized vegetable oils, trans isomerization during frying, and synthetic conjugated FA (CFA) supplements. Partial hydrogenation and heat-treated oils result in a random distribution of TFA isomers, whereas rTFAs contain specific isomers resulting from enzymatic processes. Reviews of human observational and metabolic intervention studies have suggested that consumption of rTFAs at current levels should not raise health concerns. However, these studies were not based on rTFA levels currently sold in retail markets. Current feeding practices of ruminants result in higher total TFAs with trans-18:1 isomers other than vaccenic acid, and many CFAs other than rumenic acid. The definition of TFA adopted by several countries does not distinguish among isolated TFAs of concern and ignores CFAs that should be included in total TFA due to their negative health effects. Accurate TFA definition establishment and nutritional assessment of individual TFA isomers is needed for labeling purposes. Also required are adoptions of analytical methods to resolve all TFA isomers. This information can then be used to construct a database and as a basis for meaningful recommendations. Practical applications: Areas that require further investigations have been identified: 1) Establish a uniform TFA nomenclature based on chemical structure. 2) Standardize, assess and normalize appropriate methodologies for the analysis of TFAs. 3) Synthesize pure reference standards for TFA identification. 4) Report total TFA levels with undesirable biological activities rather than total TFA content. 5) Assess the nutritional characteristics of individual TFAs independent of their origin. 6) Develop strategies to increase the content of desirable TFA isomers in ruminants. 7) Identify potential bioactive trans metabolites produced from PUFAs in ruminants. 8) Develop labeling regulations based on specific chemical structures and physiological effects regardless of their origin. 9) Construct an accurate database complemented with specific surveys of ruminant product fatty acid (FA) composition that can be accessed by regulatory agencies to make appropriate TFA recommendations.