Conjugated linoleic acid, or CLA, is a naturally occurring fat found in high quantities in certain foods. It has become a popular dietary supplement for its reported benefits as a weight-loss aid. CLA has also been researched for its role in cancer prevention.
CLA is created in the intestines of grazing animals, particularly cows. Bacteria that exist in these animals interact with omega-6 fatty acids, making modifications to them. CLA is, therefore, a modified form of the omega-6 fatty acid. It occurs in especially high quantities in beef and milk. Many supplement manufacturers sell CLA, claiming it reduces body fat and promotes muscle growth. While there are no regulatory agencies that test supplements to verify such claims, there is limited research backing CLA's use in weight loss.
Weight Loss Research
Multiple studies have been conducted on the efficacy of CLA as a tool in weight reduction. A 2007 meta-analysis published in the “American Journal of Clinical Nutrition” reviewed 18 CLA studies, concluding that CLA, when taken at a dose of 3.2 grams per day, can bring about a small decrease in body fat. A 2012 study published in “Nutrition” found that 12 weeks of CLA supplementation in overweight Chinese subjects resulted in lowered weight with no adverse effects. Not all studies have found CLA to be effective. A 2003 study published in the “Journal of Lipid Research” concluded that CLA supplementation has no effect on weight loss in humans.
A 1994 paper published in “Cancer” notes that CLA is a powerful anti-carcinogen, with effectiveness in treating tumors. The paper also states that CLA is unique because its cancer-fighting properties are present at levels of normal dietary consumption. A 2005 paper published in “Critical Reviews in Food Science and Nutrition” notes that CLA's anti-tumor properties are of special interest and that CLA suppresses cancer development at relatively low dietary levels. A 2006 study published in the “British Journal of Nutrition” found that CLA may work best when combined with other fatty acids present in beef.
Dosage and Safety
NYU Langone Medical Center notes that normal CLA doses range from 3 to 5 grams per day. The center also recommends purchasing a reputable brand to avoid contaminants. Although CLA supplementation generally appears to be safe, the 2003 study in “Journal of Lipid Research” noted that CLA supplements “may actually have adverse effects on human health.” CLA that comes from food, however, doesn't cause this concern
- Columbia Health Go Ask Alice: Conjugated Linoleic Acid (CLA) and Weight Loss
- The Americal Journal of Clinical Nutrition: Efficacy of Conjugated Linoleic Acid for Reducing Fat Mass: A Meta-Analysis in Humans
- Nutrition: Effect of Conjugated Linoleic Acid Supplementation on Weight Loss and Body Fat Composition in a Chinese Population
- Cancer: Conjugated Linoleic Acid. A Powerful Anticarcinogen From Animal Fat Sources
- Critical Reviews in Food Science and Nutrition: Role of the Conjugated Linoleic Acid in the Prevention of Cancer
- The British Journal of Nutrition: Beef Conjugated Linoleic Acid Isomers Reduce Human Cancer Cell Growth Even When Associated With Other Beef Fatty Acids
- NYU Langone Medical Center: Conjugated Linoleic Acid
- Journal of Lipid Research: Efficacy and Safety of Dietary Supplements Containing CLA for the Treatment of Obesity: Evidence From Animal And Human Studies