Acides gras trans : récents développements

Communication Scientifique et Technique – Direction Développement Iterg, rue Gaspard Monge, Parc Industriel F33600 Pessac

^* o.morin@iterg.com

Abstract

Some recent developments on trans fatty acids (TFA) include aspects like regulation (limited levels in food for Denmark, labelling in USA and Canada), scientific data analysed by different expert committees (Codex Alimentarius, Efsa in Europe, Afssa in France), technology with process solutions already developed (some of them, for more than 10 years) or in progress to decrease their occurrence. While most of the “natural” unsaturated fatty acids (UFA) are in the cis configuration, TFA main dietary origins are: i) products containing fats from ruminant animals (dairy products, meat…), where TFA are produced by the bacterial transformation of UFA in the rumen of animals – ii) partially hydrogenated fats (vegetable and fish oils) – iii) oils heated at high temperature (like deodorisation during refining). If the Codex Alimentarius as well as USA and Canada have adopted a definition of TFA excluding conjugated linoleic acids (CLAs), or in the case of Denmark, excluding also the TFA from “natural” origin, the European and French Authorities (Efsa and Afssa) define TFA as any UFA (MUFA or PUFA) having at least one double bond in the trans configuration. TFA dietary intake surveys show a significant trend to decrease, but all the countries do not start from the same point (USA, Canada four times more than Greece, for instance). Within European countries, TFA consumptions are at least ten times lower than saturated fatty acids (SAFA) intakes. 60% of the TFA intake contributing food are from animal origins (Afssa report). Considering the health effects of TFA, it is well established now that, as for SAFA, higher intakes (when compared to cis MUFA and PUFA) increase the LDL-cholesterol level, and tend to decrease HDL-cholesterol (when compared to SAFA and cis MUFA and PUFA), with a linear dose-response and a probable threshold under which no effect can be observed (Aquitaine study). The nutritional status of CLAs is not that clear, and the expert position remain cautious on their positive impact. Besides these considerations, it has to be noted that the analytical determinations of TFA together with CLAs and other fatty acids (cis) may require some sophisticated methodologies. Moreover, some technical solutions have been found, encouraged by good practice manufacturing codes (like IMACE, FEDIOL) for margarines, spreads formulation and polyunsaturated vegetable oil refining. Nevertheless, some improvements should be made for certain products (bakery, confectionery, crackers…) still contributing to TFA intakes. This specific concern on TFA should not obliterate the fact that, as far as lipids are concerned in nutritional balance, the whole diet must be considered to reach the nutritionist recommendations on SAFA/MUFA/PUFA with an optimal n-6/n-3 ratio of 5.