Temporal changes in dietary fats: Role of n6 polyunsaturated fatty acids in excessive adipose tissue development and relationship to obesity.

Key Findings:

Evidence from animal and human studies reviewed here indicate a significant increase in the n6 PUFA content and in the LA/LNA ratio of breast milk and most foods over the last decades. ALA and the ratio of LA/ALA ratio, alters the production of AA which effects pro-inflammatory and thrombotic states. In the last 40 years in France, the daily fatty acid intake has increased 1.4 fold with an increase in the consumption of LA (2.5 fold) and AA (2.3 fold). The consumption of ALA has decreased by 40 percent, leading to a 2.9 fold and a 4.2 fold increase in the ratios of n6 to n3 PUFAs and LA/ALA. The significant change in the composition of the various fatty acids can be traced to changes in processing of foods and in the feeding of animals.

ABSTRACT:

The importance of a high fat intake in the increasing prevalence of childhood and adult obesity remains controversial. Moreover, qualitative changes (i.e. the fatty acid composition of fats) have been largely disregarded. Herein is reviewed the role of polyunsaturated fatty acids (PUFAs) of the n6 series in promoting adipogenesis in vitro and favouring adipose tissue development in rodents during the gestation/suckling period. Epidemiological data from infant studies as well as the assessment of the fatty acid composition of mature breast milk and infant formulas over the last decades in the Western industrialized world are revisited and appear consistent with animal data. Changes over decades in the intake of n6 and n3 PUFAs, with a striking increase in the linoleic acid/alpha linolenic ratio, are observed. In adults, using a consumption model based upon production data, similar changes in the PUFA content of ingested lipids have been found for France, and are associated with an increase of fat consumption over the last 40 years. These profound quantitative and qualitative alterations can be traced in the food chain and shown to be due to changes in human dietary habits as well as in the feeding pattern of breeding stock. If prevention of obesity is a key issue for future generations, agricultural and food industry policies should be thoroughly re-evaluated. (Authors abstract)