Intake of conjugated linoleic acid, or CLA, is low in conventional diets, but high-dose supplements are available now that research suggests a beneficial effect on cardiovascular disease, diabetes, body composition, and immune and bone health. CLAs are naturally found in meat and milk from ruminant animals, and represent a source of omega-6 fatty acids. There are no current recommendations for dietary intake of CLA, but be aware of several safety aspects.
Basics of CLA
The term "conjugated" in CLA refers to the side-by-side positioning of double bonds in the structure of the fatty acid. Some CLAs are actually structurally trans fats, based on the orientation of their structure. Trans fats are inarguably detrimental to human health, and current recommendations suggest that you avoid them. However, CLAs do not appear to have the same health consequences, so they are classified as omega-6 fatty acids. Conjugated linoleic acids are generated in the stomachs of ruminant animals. Ruminants are animals -- including cows, sheep, goats, and camels -- with the ability to ferment their foods before digestion because their stomachs are split into multiple compartments. The stomach is where bacteria and enzymes alter the structure of linoleic acid, another omega-6 fatty acid found in plant oils and nuts, and in the diet of these animals.
The main dietary sources of CLA are ruminant meats and dairy products. According to the U.S. Department of Agriculture Nutrient Database, the most potent source of natural CLAs is beef, which contains between 0.27 and 0.90 grams per 100-gram serving. In addition, conjugated linoleic acid makes up 0.3 percent to 0.7 percent of total milk fat in milk products. Other sources include lamb and goat meat, and butter.
Fortified and Supplemental Sources
Several fortified foods and a huge range of supplements contain CLA. Look for exercise-oriented products such as CLA-fortified chocolate milk. Supplements contain significantly higher concentrations than what is found in natural sources. For example, a 2001 study in the journal "Lipids" that examined the effect of CLA on metabolic factors and body composition used a dose of 4.1 grams per day. In the United States, approved supplements containing CLA range in dose from 0.7 to 3 grams.
Specific dietary recommendations for CLA have not been established, so follow recommendations for omega-6 fatty acids. The American Dietetic Association suggests that 3 percent to 10 percent of your daily fat intake should come from omega-6 sources. For a person consuming 2,000 calories per day, this would translate to 7 to 22 grams of omega-6 fatty acids a day. A study published in 2001 in the Nutrition Research Journal estimated that the average intake of healthy adults in North America was 94.9 mg per day, but intakes varied greatly depending on dietary patterns.
Consumers should be aware that high intakes of CLA have been associated with an increased risk for insulin resistance, and several other adverse health outcomes. Before taking high-dose supplements, consult a qualified healthcare practitioner. In regards to CLAs from natural sources, consult standard recommendations for dietary fat.
- Journal of the Academy of Nutrition and Dietetics: Position of the Academy of Nutrition and Dietetics: Total Diet Approach to Healthy Eating
- Journal of the Academy of Nutrition and Dietetics: Position of the Academy of Nutrition and Dietetics: Dietary Fatty Acids for Healthy Adults
- Journal of the American Dietetic Association: Position of the American Dietetic Association and Dietitians of Canada: dietary fatty acids.
- The Journal of Nutrition: Conjugated linoleic acid is synthesized endogenously in lactating dairy cows by Delta(9)-desaturase
- Nutritional Ecology of the Ruminant; Soest, PJV.
- United States Department of Agriculture: National Nutrient Database for Standard Reference
- Nutra Ingredients: First US CLA milk launched to "local" Acclaim
- NIH Dietary Supplement Label Database: Conjugated Linoleic Acid
- Nutrition Research: An assessment of c9,t11 linoleic acid intake in a small group of young Canadians
- Diabetologia: Supplementation with trans10cis12-conjugated linoleic acid induced hyperproinsulinaemia in obese men: close association with impaired insulin sensitivity