Grass-fed beef has higher concentrations of CLA than grain-fed beef.
Conjugated linoleic acid is a type of fat found in certain types of meat and dairy foods. Due to CLA's purported ability to aid in fat loss, dietary supplements using this fatty acid have also been developed. The evidence regarding the weight-loss effects of CLA is conflicting, however. If you are interested in consuming dietary CLA, it is found in high levels in ruminant animals.
CLA's Weight-Loss Potential
Many of the studies done on CLA have used the supplemental form. A study published in 2012 in "Nutrition" found that CLA supplementation for 12 weeks reduced the incidence of obesity, without any negative effects. A 2007 meta-analysis published in the "American Journal of Clinical Nutrition" noted that CLA has shown to be inconsistent in producing weight loss. After analyzing 18 studies, however, the researchers concluded that a dose of 3.2 grams of CLA per day could produce a modest reduction in body fat.
CLA in Ruminant Animals
According to a 2009 paper published in "Nutrition and Metabolism," CLA is found predominantly in "milk, milk products, meat and meat of ruminants." Ruminant animals consume grass and other vegetation. Examples include cattle, buffalo, goats, sheep, deer and elk. These animals possess a digestive system that allows them to convert plant matter into nutritious food, notes the U.S. Environmental Protection Agency.
Beef and dairy are among the most commonly consumed foods containing high amounts of CLA. While all beef and dairy products contain CLA, the products that come from grass-fed cattle may be higher in the fatty acid. According to a 2010 review published in "Nutrition Journal," consumers have become more interested in grass-fed beef products, due to their perceived health advantages. The authors note that grass-fed diets can improve the fatty acid composition, antioxidant content and CLA concentrations in beef and beef products. Therefore, if you're looking to get the most CLA out of your beef products, it may be advantageous to choose grass-fed options.
Foods Highest in CLA
The Dairy Nutrition website reports that some of the richest sources of CLA, measured in milligrams per serving, include 4 ounces of sour cream at 78.7; 3 ounces of lamb, 73.5; 2 ounces of cheddar cheese, 68.1; and 2 ounces of American cheese, 61.5. Other foods with a significant CLA in milligrams per serving include 1 tablespoon of butter at 55.0; 3 ounces of fresh ground beef, 52.9; 4 ounces of ice cream, 42.5; 8 ounces of cultured buttermilk, 28.1; and 6 ounces of plain yogurt, 23.5. It is important to note that the CLA content of these foods changes with the season, as well as the diet of the animal.
According to New York University Langone Medical Center, the typical dose of CLA for weight loss ranges between 3 and 5 grams per day. The medical center reports that it would be very difficult to consume this amount through dietary sources, making supplemental CLA the only practical source, in terms of promoting weight loss. CLA supplements are generally considered safe, though they are not recommended for nursing mothers. Safe doses of supplemental CLA have not been established for children, pregnant women or those with liver or kidney disease.