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Abstract
The definition and evaluation of trans fatty acids (TFA) with regard to foodstuffs and health hazard are not consistent. Based on the current situation, the term should be restricted only to TFA with isolated double bonds in trans-configuration. Conjugated linoleic acids (CLA) should be separately assessed. Ideally, the origin of the consumed fat should be declared, i.e., ruminant TFA (R-TFA) and industrial TFA (non-ruminant; I-TFA). In ruminant fat, more than 50% of R-TFA consists of vaccenic acid (C18:1 t11). In addition, natural CLA, i.e., c9,t11 CLA is also present. Both are elevated in products from organic farming. In contrast to elaidic acid (t9) and t10, which occur mainly in partially hydrogenated industrial fat, t11 is partially metabolized into c9,t11 CLA via Δ9-desaturation. This is the major metabolic criterion used to differentiate between t11 and other trans C18:1. t11 indicates health beneficial effects in several studies. Moreover, CLA in milk fat is associated with the prevention of allergy and asthma. An analysis of the few studies relating to R-TFA alone makes clear that no convincing adverse physiological effect can be attributed to R-TFA. Only extremely high R-TFA intakes cause negative change in blood lipids. In conclusion, in most European countries, the intake of R-TFA is assessed as being low to moderate. Restriction of R-TFA would unjustifiably represent a disadvantage for organic farming of milk.
ACKNOWLEDGMENT
The authors would like to thank Dr. Ulrich Schäfer for the proofreading and Nasim Krögel for the language editing of the manuscript.
CONFLICT OF INTEREST
The authors declare that they have no competing interests.
AUTHOR CONTRIBUTIONS
GJ and KK initiated the review. KK was responsible for the literature review and organization of the review, composition of the unpublished results and tables, statistical analysis, created the manuscript, and worked through the submission process. CD conducted a portion of the literature review, provided unpublished data, and served as editor for the manuscript. GJ created a portion of the manuscript, provided unpublished data, and served as editor for the manuscript. All authors read and approved the manuscript.
ABBREVIATIONS
| CLA | = | Conjugated linoleic acids |
| CLnA | = | Conjugated linolenic acids |
| CVD | = | Cardiovascular disease |
| I-TFA | = | Industrially derived trans fatty acids (non-ruminant) |
| PHVO | = | Partially hydrogenated vegetable oils |
| PUFA | = | Polyunsaturated fatty acids |
| R-CLA | = | Ruminant-derived CLA |
| R-TFA | = | Ruminant-derived trans fatty acids; |
| SFA | = | Saturated fatty acids |
| t11 | = | Vaccenic acid (C18:1 trans11) |
| t9 | = | Elaidic acid (C18:1 trans9) |
| TAG | = | Triacylglycerides |
| TC | = | Total cholesterol |