A survey of the total content of trans-18:1 acids and their detailed profile in French food lipids was conducted in 1995-1996, and 1999. For this purpose, 37 food items were chosen from their label indicating the presence of partially hydrogenated vegetable oils (PHVO) in their ingredients. The content as well as the detailed profile of these isomers was established by a combination of argentation thin-layer chromatography and gas liquid chromatography (GLC) on long polar capillary columns. With regard to the mean trans-18:1 acid contents of extracted PHVO, a significant decrease was observed between the two periods, i.e., from 26.9 to 11.8% of total fatty acids. However, only minor differences were noted in the mean relative distribution profiles of individual trans-18:1 isomers with ethylenic bonds between positions delta4 and delta16 for the two periods. The predominant isomer was delta9-18:1 (elaidic) acid, in the wide range 15.2-46.1% (mean, 27.9+/-7.2%) of total trans-18:1 acids, with the delta10 isomer ranked second, with a mean of 21.3% (range, 11.6 to 27.4%). The content of the unresolved delta6 to delta8 isomer group was higher than the delta11 isomer (vaccenic acid), representing on average 17.5 and 13.3%, respectively. Other isomers delta4, delta5, delta12, delta13/delta14, delta15, and delta16, were less than 10% each: 1.0, 1.6, 7.4, 7.1, 1.8, and 1.0%, respectively. However, considering individual food items, it was noted that none of the extracted PHVO were identical to one another, indicating a considerable diversity of such fats available to the food industry. A comparison of data for French foods with similar data recently established for Germany indicates that no gross differences occur in PHVO used by food industries in both countries. Estimates for the absolute mean consumption of individual isomers from ruminant fats and PHVO are made for the French population and compared to similarly reconstructed hypothetical profiles for Germany and North America. Differences occur in the total intake of trans-18:1 acids, but most important, in individual trans-18:1 isomer intake, with a particular increase of the delta6-delta8 to delta10 isomers with increasing consumption of PHVO. It is inferred from the present and earlier data that direct GLC of fatty acids is a faulty procedure that results (i) in variable underestimates of total trans-18:1 acids, (ii) in a loss of information as regards the assessment of individual isomeric trans-18:1 acids, and (iii) in the impossibility of comparing data obtained from human tissues if the relative contribution of dietary PHVO and ruminant fats is not known.

If an increased consumption of alpha-linolenic acid (ALA) is to be promoted in parallel with that of n-3 long-chain-rich food, it is necessary to consider to what extent dietary ALA can be absorbed, transported, stored, and converted into long-chain derivatives. We investigated these processes in male hamsters, over a broad range of supply as linseed oil (0.37, 3.5, 6.9, and 14.6% energy). Linoleic acid (LA) was kept constant (8.5% energy), and the LA/ALA ratio was varied from 22.5 to 0.6. The apparent absorption of individual FA was very high (>96%), and that of ALA remained almost maximum even at the largest supply (99.5%). The capacity for ALA transport and storage had no limitation over the chosen range of dietary intake. Indeed, ALA intake was significantly correlated with ALA level not only in cholesteryl esters (from 0.3 to 9.7% of total FA) but also in plasma phospholipids and red blood cells (RBC), which makes blood components extremely reliable as biomarkers of ALA consumption. Similarly, ALA storage in adipose tissue increased from 0.85 to 14% of total FA and was highly correlated with ALA intake. As for bioconversion, dietary ALA failed to increase 22:6n-3, decreased 20:4n-6, and efficiently increased 20:5n-3 (EPA) in RBC and cardiomyocytes. EPA accumulation did not tend to plateau, in accordance with identical activities of delta5- and delta6-desaturases in all groups. Dietary supply of ALA was therefore a very efficient means of improving the 20:4n-6 to 20:5n-3 balance.

Apports alimentaires en acides linoléique et alpha-linolénique d'une population d'Aquitaine Linoleic and alpha-linolenic acids supplied by food in a population group in AquitaineOléagineux, Corps Gras, Lipides. Résumé : Les apports alimentaires quotidiens en acides linoléique (18:2 n-6) et alpha-linolénique (18:3 n-3) ont fait récemment l'objet de recommandations pour la population française (ANC 2001). Cependant, peu d'informations sont actuellement disponibles sur la situation réelle, en particulier vis-à-vis du 18:3 n-3. Cette étude montre que la consommation de 18:2 n-6, en Aquitaine (n = 140 femmes), représente en moyenne 4,4 % (± 1,8) de l'apport énergétique total (AET), valeur acceptable par rapport aux ANC (4 %). En revanche, l'apport en 18:3 n-3 est insuffisant (0,34 ± 0,1 % au lieu de 0,8 % recommandé). Dans cette population, le 18:3 n-3 est à 75 % d'origine animale. La contribution des huiles est faible (9 %). La teneur moyenne en 18:2 n-6 et 18:3 n-3 du tissu adipeux des sujets est respectivement égale à 14 % et 0,5 % des acides gras totaux. Dans le plasma, ce sont les esters de cholestérol (EC) qui en véhiculent le plus (53 % de 18:2 n-6 et 0,42 % de 18:3 n-3). Cette étude met en évidence une corrélation positive entre les pourcentages de 18:2 n-6 dans les EC plasmatiques et ceux du tissu adipeux (r = 0,606 et p < 0,001), confirmant que cette fraction plasmatique est un « marqueur » non invasif des apports en acide linoléique.Mots-clés : consommation française, acide linoléique, acide alpha-linolénique, biomarqueurs. Summary :The levels of dietary supply with linoleic acid (LA) and alpha-linolenic acid (LNA) have been revised for French people. However, few data of real intake are actually available, especially regarding LNA. This study shows that, in Aquitaine (n = 140 women), average LA supply (4.4 ± 1,8% of total energy) is in accordance with the recommended value (4%), whereas LNA supply is too low (0.34 ± 0.1% versus 0.8%). Three quarters of total LNA are provided by animal fats. In adipose tissue, LA and LNA levels represent respectively 14% and 0.5% of total fatty acids. In plasma, these fatty acids are mainly incorporated into cholesterol esters (CE) (53% LA and 0.42% LNA). Moreover, LA percentage value in CE is positively correlated with that found in adipose tissue (r = 0.606; p < 0.001). Therefore, plasma CE could be used as a non-invasive indicator of LA intake.

This study reports the fatty acid composition of subcutaneous adipose tissue in French women with special emphasis on the content of trans fatty acids originating from two main dietary sources, ruminant fats and partially hydrogenated vegetable oils (PHVO). Adipose tissue trans fatty acid levels from 71 women, recruited between 1997 and 1998, were determined using a combination of capillary gas chromatography and silver nitrate thin-layer chromatography. Results indicate that on average cis monounsaturates accounted for 47.9% of total fatty acids, saturates for 32.2%, and linoleic acid for 14.4%. Cis n-3 polyunsaturates represented only 0.7%. Total content of trans fatty acids was 2.32 +/- 0.50%, consisting of trans 18:1 (1.97 +/- 0.49%), trans 18:2 (0.28 +/- 0.08%), and trans 16:1 (0.06 +/- 0.03%). Trans 18:3 isomers were not detectable. The level of trans fatty acids found in adipose tissue of French women was lower than those reported for Canada, the United States, and Northern European countries but higher than that determined in Spain. Therefore, trans fatty acid consumption in France appears to be intermediate between that of the United States or North Europe and that of Spain. Based on the equation of Enig et al., we estimated the mean daily trans 18:1 acid intake of French women at 1.9 g per person. The major trans 18:1 isomer in adipose tissue was delta11 trans, as in ruminant fats. Estimates of relative contribution of trans fatty acid intake were 55% from ruminant fats and 45% from PHVO. This pattern contrasts sharply with those established for Canada and the United States where PHVO is reported to be the major dietary source of trans fatty acids.

Gender and dietary fatty acids are involved in the regulation of lipid metabolism, disturbances of which can lead to pathologies such as metabolic syndrome or CVD. Possible interactions between these factors were investigated in male and female hamsters fed diets rich in either saturated fatty acids ('butter' diet) or in a-linolenic acid ('linseed oil' diet). Gender effect predominated over the diet effect on cholesterol (CH) metabolism; compared to males, females exhibited lower concentrations of plasma total CH (220 %, P,0·001), LDL-CH (240 %, P,0·001) and HDL-CH (2 16 %, P, 0·001), together with higher LDL receptor (þ 40 %) and lower HDL receptor (260 %) hepatic content. Triacylglycerol (TG) metabolism was affected by diet above all: compared to animals fed the 'butter' diet, those fed the 'linseed oil' diet exhibited lower plasma (223 %, P¼0·046) and liver TG (220 %, P¼ 0·026) concentration which may result from both an increased b-oxidation (P,0·001), without any change in PPARa mRNA, and a decreased hepatic lipogenesis (P¼ 0·023), without increased sterol response element binding protein 1c (SREBP1c) mRNA. The response to diet was much more pronounced in males than in females, without gender effect on the transcription level of PPARa and SREBP1c. Finally, the 'linseed oil' diet decreased the insulin resistance index (2 80 %, P,0·001) with a more marked effect in males, in relation to their higher hepatic PPARg expression (þ 90 %, P¼ 0·012). In conclusion, in our model, the response of either TG or CH to dietary fatty acids is modulated differently by gender. The possible relevance of these interactions to dietary practice should be taken into account in man.a-Linolenic acid: Gender: Lipid metabolism: Dietary fatty acids