Evaluation of Health Benefits of Conjugated Linoleic Acid (CLA)-Enriched Dairy and Beef Foods

Project Overview

Project Type: Research and Education
Funds awarded in 2004: $150,000.00
Projected End Date: 12/31/2007
Region: North Central
State: Iowa
Project Coordinator:
Teresa Steffens
Resource Conservation and Development for Northeast Iowa, Inc

Annual Reports


  • Agronomic: barley, grass (misc. perennial), hay
  • Animals: bovine
  • Animal Products: dairy


  • Animal Production: feed formulation, free-range, feed/forage
  • Crop Production: cover crops
  • Education and Training: farmer to farmer, on-farm/ranch research, participatory research
  • Farm Business Management: feasibility study
  • Sustainable Communities: partnerships, urban/rural integration


    NE Iowa RC&D, Inc., Iowa State University, Coolee Region Organic Producers, and local producers joined to carry out a second project that will be a human feeding study using Conjugated Linoleic Acid (CLA) enriched food items verses non-CLA items. The purpose of this research will be to verify the health benefits of this acid in humans, to quantify how much CLA needs to be ingested to have an effect on health, as well as creating new practices for farmers to enhance the diets of their livestock to obtain an increased level of CLA in the final product.


    Various isomers of conjugated octadecadienoic acid, also known as conjugated linoleic acid, have been cited as both improving health and inciting debilitating disorders. A wide variety of models have been used to determine the health implications of CLA consumption, including mice, rats, animal and human cell and tissue cultures, and humans. The methods of presenting CLA to the models have been just as varied. To date, only one study has investigated the effects of feeding dairy products high in CLA by dietary manipulation to humans (1). However, no studies have been conducted in which products naturally enriched with CLA have been fed to humans.

    Feeding patterns and practices of ruminant livestock are known to alter the fatty acid composition of products derived from these animals. In particular, bovine animals consuming pasture during the rainy seasons tend to produce the highest natural concentrations of CLA (2).

    One of many reported health effects of CLA is that of modulating lipoprotein profiles. Tricon et al have reported that in humans different isomers of CLA have opposing effects on circulating cholesterol concentrations: t10,c12 CLA improves lipoprotein profiles, whereas c9,t11 CLA deteriorates them (3). Other studies, however, have indicated that the c9,t11 isomer can decrease atherogenicity (4), and still others have shown no effect of CLA at all (1,5).

    Another purported health benefits is hepatic health. In mouse and rat studies, CLA has been shown to decrease hepatic steatosis and alleviate the nonalcoholic fatty liver disease (6-8), though at least one study has concluded that CLA can be used to induce fatty liver (9). In humans, however, Iwata et al. showed little change in markers of liver function, with statistically significant changes being physiologically insignificant (10).

    Other studies relate to improved and impaired insulin resistance and glucose intolerance (11,12), adiponectin modulation (11,13,14), and body composition (15,16). The benefits include decreasing the onset of diabetes symptoms and other markers of the metabolic syndrome, and the impairments have shown the exact opposite.

    As briefly mentioned, different isomers may have different effects on health outcomes. Because no study has been done feeding the naturally occurring isomeric ratios in a natural food matrix such as that provided by pasture-fed cattle, the health effects are, for the most part, observations of synthetic, artificial, or manufactured products. With this in mind, the present study is designed to determine if human markers of health will be altered with the consumption of CLA in a natural food matrix.

    Project objectives:

    This project will conduct an experiment that evaluates CLA-enriched dairy and beef foods from farmers on contract with CROPP. The farmers will use grazing systems to raise livestock and produce dairy products with high CLA content for the experiment. The milk and beef they produce will be processed and then prepared to create several different foods that will be incorporated into typical U.S. diets for a human feeding study. The study then will examine the health benefits of humans consuming CLA-enriched dairy and beef foods by evaluating the effect of feeding diets containing these CLA-enriched foods on concentration of cholesterol, individual lipoproteins, glucose, glucagon, and insulin in blood plasma, bone density, body weight and composition, and glucose tolerance. Results will be widely distributed through publication, field days and presentations. Several positive project outcomes are expected.

    Short-term outcomes of the project will enhance the quality of life for participants and encourage sustainable agricultural systems.

    Specific short-term outcomes include improved human health, quantified through the direct effects of CLA-enriched foods on measures of human health.

    Because pasture feeding is the management system found to produce CLA-enriched foods, (outcome of our current SARE-funded project), intermediate outcomes of this research will improve the profitability for farmers that utilize sustainable management systems including greater economic viability for dairy and beef producers that use sustainable high CLA pasture systems. Once the benefit to humans is demonstrated, high CLA content meat and dairy products are expected to increase in market value. Therefore, producers using the sustainable, high CLA pasture system, will be able to obtain a premium price in new and emerging markets and increase the market share for high CLA content pasture-fed animals.

    The long-term outcomes of this project will enhance the quality of life for farmers and ranchers, rural communities, and society as a whole by providing a better understanding of CLA as an indicator that links healthy lands and healthy animals to healthy humans.

    Long-term benefits will include improved health of the land and of human communities. This will be accomplished through a demonstration of the economic, environmental, and health justifications of management systems that result in greater utilization of pasture-based feeding systems for production of animal-derived foods on marginal land.

    Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.