Posted 14 September 2015
A 26-year-old woman who had recently lost approximately 23 kg was admitted to hospital with stomach pain, nausea, and vomiting. She had started taking conjugated linoleic acid (CLA) supplements, which are often advertised as being able to reduce body fat, one week prior. She was ultimately diagnosed with the first case of hepatitis associated with CLA supplement use in the United States. This is only the third documented case worldwide.
Bilal M, Patel Y, Burkitt M, Babich M. Linoleic Acid Induced Acute Hepatitis: A Case Report and Review of the Literature. Case Reports Hepatol. 2015;2015:807354.
How effective is CLA in reducing body fat?
The most recent review of studies assessing whether CLA results in weight loss, concludes: “The evidence from RCTs (randomized clinical trials) does not convincingly show that CLA intake generates any clinically relevant effects on body composition on the long term.”
Onakpoya IJ, Posadzki PP, Watson LK, Davies LA, Ernst E.. The efficacy of long-term conjugated linoleic acid (CLA) supplementation on body composition in overweight and obese individuals: a systematic review and meta-analysis of randomized clinical trials. Eur J Nutr. 2012 Mar;51(2):127-34. doi: 10.1007/s00394-011-0253-9.
Numerous supplements containing conjugated linoleic acid (CLA) are presently being promoted for body weight reduction. The aim of this systematic review is to evaluate the evidence for or against the long-term efficacy of CLA.
Electronic searches were conducted to identify relevant randomized clinical trials (RCTs). No restrictions in age, time, or language were imposed. Studies had to be at least 6 months in duration. Three reviewers independently determined the eligibility of studies. Two reviewers independently extracted data and assessed the reporting quality of all RCTs.
Fifteen RCTs were identified, and seven were included. Four of the included RCTs had serious flaws in the reporting of their methodology. A meta-analysis revealed a statistically significant difference in weight loss favouring CLA over placebo (mean difference: -0.70 kg; 95% confidence interval: -1.09, -0.32). Our meta-analysis also revealed a small significant difference in fat loss favouring CLA over placebo (MD: -1.33 kg; 95% CI: -1.79, -0.86; I (2) = 54%). The magnitude of these effects is small, and the clinical relevance is uncertain. Adverse events included constipation, diarrhea, and soft stools.
The evidence from RCTs does not convincingly show that CLA intake generates any clinically relevant effects on body composition on the long term.
Natural Medicines Comprehensive Database rates the effectiveness for this claim as “POSSIBLY EFFECTIVE”: “Taking conjugated linoleic acid (CLA) orally seems to improve body composition in patients who are overweight or obese. Taking 1.8 to 6.8 grams daily seems to decrease body fat mass (BFM), increase lean body mass (LBM), and reduce waist and hip circumference in some patients (2819,3153,4947,13137,45295,45303,45685,45799). However, CLA does not seem to reduce total body weight or body mass index (BMI) in many studies (2819,2821,3153,10410,13137,45007,45790), although taking CLA 8 grams daily for 16 weeks seems to reduce BMI in obese, postmenopausal women with type 2 diabetes (45614).”
NMCD also cautions:
“There is evidence that the isolated trans-10,cis-12 isomer of CLA can increase hyperproinsulinemia and insulin resistance in patients with abdominal obesity (2821,13026,13137). Hyperproinsulinemia is an independent risk factor for type 2 diabetes and cardiovascular disease. Therefore, CLA might not be a good choice for obese patients; however, most commercial CLA products contain a mixture of CLA isomers. It is not known if these mixed CLA isomer products have this same risk”.