Teneurs en acides gras polyinsaturés essentiels du lait maternel en France : évolution du contenu en acides linoléique et alphalinolénique au cours des 10 dernières années

Abstract

Background: Long-chain polyunsaturated fatty acids (LC-PUFA) are nutritionally important constituents of breast milk to support normal growth, immune function and central nervous system development of newborn infants. Both linoleic acid (18:2 n-6; LA) and alpha-linolenic acid (18:3 n-3; ALA), the essential fatty acids, precursors of n-6 and n-3 LC-PUFA, are also present in breast milk. Although the total amount of fat in human milk is fairly constant, the fatty acid composition can vary substantially depending on the diet of the mother. Large variations in the LA, ALA and DHA (22:6 n-3) contents are observed among countries. As reported by previous studies (1993-2001), the ALA consumption of the French population was 2-3 times lower than the recommended value. Since this period, the food industry offers more food products enriched in n-3 fatty acids. Objective: The present study aimed to investigate whether current recommendations and improved n-3 PUFA content of food products comply with the actual breast-milk PUFA composition. For this purpose, the PUFA content of a large number of human milk samples collected in 2007 in different French regions were compared with previous data obtained in studies conducted in the nineties years (1993-1998). Moreover, this study aimed to confirm expected reduction of the trans fatty acid (TFA) intake resulting from decreased level of TFA in margarine and other dietary fats during the same period. Study design and methods: Mature (postpartum day ≥ 30) human milk samples (n = 145) were provided in 2007 by eight French regional human milk banks (Bordeaux : n = 20; Dijon: n = 21; Ile-de-France: n = 18; Lyon: n = 20; Montpellier: n = 18; Nantes: n = 21; St Etienne: n = 6; Tours: n = 21), from healthy women volunteers with no particular health history. The fatty acid composition of breast milk was analysed by high-resolution gas-liquid chromatography. Statistical analysis was performed with Kruskall Wallis and Mann and Whitney U tests (p < 0.05). Results: Fatty acid composition of human milk samples did not differ significantly among the eight French regions. The proportions of saturated fatty acids were relatively similar (means ranging from 44.9% to 48.7% of total fatty acids). Monounsaturated fatty acids also varied little, from 36.9% to 39.7%. Total n-6 and n-3 PUFA accounted for 12.5%-15.2%, with an n-6/n-3 PUFA ratio close to 10, similar among the collect centers. Considering the overall results, LA represented between 10.4% and 12.7%, and ALA varied from 0.72% to 0.95%. Comparison of our results to previous data (1993-1998) showed opposite changes for LA and ALA. During the last decade, the LA level has decreased by 17%, whereas the ALA level has increased by 45%, and hence in 2007, the LA/ ALA ratio was close to 14 versus 24 in 1993-1998. The LC-PUFA content remained unchanged. Concerning total TFA, their content was lower (– 37%; p < 0.0001) in 2007 than in 1997, respectively 1.3% and 2.1% of total fatty acids of breast milk. Conclusion: Basing on the PUFA composition of human milk, this large French study shows favourable changes in consumption of both omega-6 and omega-3 fatty acid precursors, and in TFA, in the course of last decade.