Milk Fatty Acids: Retail Milk Fat Composition And Efforts To Naturally Enhance Bioactive Fatty Acids In Milk For The Benefit Of Human Health

Abstract

Consumers are increasingly aware of the connection between diet and heath, and the nutrient composition of foods is required to appropriately assess dietary intake and establish recommendations. The last survey of U.S. commingled milk was in 1984 and since then, substantial improvements in the analytical techniques of fatty acids (FA) have allowed for a more detailed isomer profile. Milk contains bioactive FA shown to have potent anticarcinogenic and antiatherosclerotic properties, such as conjugated linoleic acid (CLA) and omega-3 FA. The first objective was to evaluate current FA composition of retail milk in the U.S. to include 1) regional and seasonal differences, and 2) differences among unlabeled conventional milk and milk labeled rbST-free or organic. While statistical significance was reported for most FA by geographic region and season as well as among label type, numerical differences were minor, having little or no public health relevance. These results indicate that the increased use of total mixed rations, lipid supplements and by-product feeding must be well established across all geographic regions and seasons. In addition, when combined with previous analysis, results indicate that all milk is wholesome and nutritious regardless of production management practice. Milk FA composition is highly affected by diet, thus the second objective was to naturally enhance CLA and omega-3 FA in milk fat through the use of dietary lipid supplements. The first two studies utilized soybean oil or linseed and fish oil to enhance milk bioactive FA, with the inclusion of a high dose of dietary vitamin E to mitigate diet-induced milk fat depression (MFD) caused by lipid supplementation. CLA content in milk fat markedly increased with lipid supplementation, however vitamin E had no effect. Lastly, a genetically-modified soybean oil enhanced with stearidonic acid (SDA) was fed and resulted in impressive increases of omega-3 FA in milk fat. Human consumption of omega-3 FA are well below dietary recommendations, and SDA enhanced milk may serve as a novel dietary source of these FA. Methods to enhance bioactive FA in milk fat continue to be investigated, thus establishing the potential for improved human health through the consumption of dairy products.