W1181: Modifying Milk Fat Composition for Improved Nutritional and Market Value
Statement of Issues and Justification
Dairy products are an important source of vital nutrients in the human diet. Nevertheless, many health-conscious consumers perceive dairy products to contain excessive amounts of total fat, saturated fat, and cholesterol. Butter and other high-fat dairy products are excluded from diets designed to decrease blood cholesterol and prevent or treat coronary heart disease.The research of this committee has produced insights into milk fat production and methods to alter milk fat amount and composition by simple dietary means. Based on the work of individual researchers and collaboration among member research groups, knowledge has been developed that should allow milk fat to be 'tailored' in composition to meet market demands for improved fatty acid composition and milk fat levels. It has been demonstrated that nutritional manipulation can increase oleic acid content and decrease saturated fatty acid content of cow milk. Dietary manipulation can be used to decrease milk fat production and thus have a positive impact on early lactation cows in negative energy balance in terms of general health and reproduction. Allowing cows to pasture feed increases the conjugated linoleic acid (CLA) content of milk as does manipulating the fat content of the diet with grains, fish oils and calcium salt supplements. In addition, the mechanisms at a cellular level are being examined to provide clues to additional regulation that may be possible by targeting specific enzymes controlling triglyceride and phospholipid synthesis in the mammary gland. These enzymes modify fatty acid utilization through effects on de novo synthesis, uptake and transport from the blood, and desaturation and esterification of fatty acids into milk fat triglycerides. Increasing the vaccenic acid content produced in the rumen from the diet leads to increased cis-9, trans-11 CLA in the milk due to the action of the delta-9 desaturase enzyme in the mammary gland. Based on evidence from studies indicating that certain conjugated linoleic acids (CLA) and vaccenic acid are protective in animal models for some cancers, the ability to increase these in milk fat holds promise for improvement of human health. In addition, some CLA isomers have been shown to lead to decreased body fat and increased lean muscle mass in animal models. Lipids from milk and other ruminant animal products are the major natural source of this class of fatty acids.
One clear advantage of a multistate project aimed at milk fat modification is the standardization of fatty acid methods. New advances in analysis of fatty acids, including trans isomers, are occurring at a rapid pace. Members of W-181 share information on new fatty acid methods, which is then used to generate a more reliable database of milk fatty acid analysis. Also, members of the committee cooperate on projects to take advantage of lipid analysis methods available in a few, but not all locations.
Another advantage of a multistate effort on milk fat modification is the success of W-181 in bringing together expertise from industry and more than a dozen international research stations. Discussions not only occur about research results aimed at milk fat modification, but also occur about the practical implications of these results to the consumer and industry in the U.S. and around the world. Other formats do not exist to bring together this diverse level of expertise for discussions aimed at improving the nutritional value and marketing of milk.
A third advantage of the multistate project is the opportunity for committee members to provide input on the advantages and disadvantages of recommended changes in milk fat composition that are being considered as US dietary policy. An example was a previous letter from W-181 to FDA outlining the advantages and disadvantages of requiring labeling of trans fatty acids. The W-181 project allowed scientists who were directly engaged in research projects on milk fatty acids the opportunity to discuss as a group the full implications of potential policy changes and to respond to requests for expertise and input from US Regulatory Agencies.
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