Conjugated Linoleic Acid

Conjugated Linoleic Acid, CLA

Common Names

  • CLA

For Patients & Caregivers

How It Works

Conjugated Linoleic Acid (CLA) has been shown to reduce cholesterol levels. Preliminary studies in humans suggest potential anticancer effects.

CLA is commonly found in dairy products and beef, and is made by microbes that live within the gut of certain animals. It is found throughout the body and may regulate cholesterol levels and help disrupt cancer cell replication. Although CLA is marketed as a weight loss product, studies show mixed results.

Purported Uses
  • To prevent and treat cancer
    Animal studies have shown that CLA has antioxidant properties and may reduce the spread of cancer. Preliminary studies in humans suggest potential anticancer effects. However, clinical trials to confirm safety and effectiveness are needed.
  • To treat high cholesterol
    Studies show that while CLA reduces total cholesterol levels, it also reduces HDL, or good cholesterol levels.
  • To promote healthy weight
    CLA may improve body fat mass in some people, but results are mixed, and CLA may actually be harmful in some populations. For example, in obese men with metabolic syndrome or at high risk for heart disease, CLA supplementation decreased insulin sensitivity / caused insulin resistance.
Do Not Take If

You are taking blood-thinning drugs (eg, warfarin): CLA may increase the effects of anticoagulant and antiplatelet drugs, increasing the risk of bleeding.

You have diabetes: In obese men, CLA has caused insulin resistance and may increase blood glucose levels.

You have heart disease: In patients at risk for cardiovascular complications, it may increase processes that cause cell damage.

Side Effects
  • Fatigue
  • Gastrointestinal symptoms
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For Healthcare Professionals

Scientific Name
cis-9,trans-11 conjugated linoleic acid; trans-10,cis-12 conjugated linoleic acid
Clinical Summary

Conjugated Linoleic Acid (CLA) is a naturally occurring fatty acid found in the milk and meat of ruminant animals (22). CLA supplements have been marketed for weight control and to lower high cholesterol. Other purported uses include cancer prevention. CLA has different isomers that appear to have distinct characteristics, with anti-carcinogenic effects more likely attributable to cis-9,trans-11 and anti-obesity effects attributable to the trans-10,cis-12 (23) isomer.

In humans, studies of potential benefits of CLA are mixed. CLA supplemenation may have antithrombotic or antiatherosclerotic effects (24). However, in obese men at high risk for cardiovascular disease, cis-9,trans-11 CLA supplementation decreased insulin sensitivity (25). Another study suggests no significant effects on antioxidant metabolism in healthy overweight/obese individuals (26). CLA may ameliorate inflammatory bowel disease (20) and improve airway hyperreactivity in asthmatic individuals (21). Short-term high CLA intake did not affect blood pressure regulation (27).

Data from studies on CLA-induced changes in body composition and weight reduction are also mixed. Some studies yielded positive results (28) (29) (30) while others do not show benefits (31) (32) (46). Several double-blind RCTs have evaluated whether CLA can have additional effects on exercise performance. One study did not find any impact of CLA on aerobic capacity (33), and another determined that CLA did not improve aerobically-induced neuromuscular fatigue (34). However, CLA was shown to have triacylglycerol-lowering effects both on its own (22) and along with aerobic exercise (35), although it did not have any effect on other lipoprotein risk factors (22).

Animal studies suggest that CLA may play a role in reducing tumor proliferation in certain cancer cell lines (2) (3) (4). In models of colorectal cancer, CLA reduced inflammation and decreased disease activity (36) (37). Preliminary human studies suggest anticancer effects with CLA in colorectal (38) and breast (39) cancers. More studies in the context of clinical trials are needed.

Reported adverse events include minor gastrointestinal symptoms (9) and severe fatigue (6)

Food Sources

Meat and dairy products

Purported Uses
  • Cancer prevention
  • High cholesterol
  • Weight maintenance
Mechanism of Action

Of several possible CLA isomers, cis-9,trans-11 and trans-10,cis-12 are the main isomers found in meat and dairy products, as well as commercial supplements. They appear to have distinct characteristics, with anti-carcinogenic effects more likely attributable to cis-9,trans-11 and anti-obesity effects attributable to trans-10,cis-12 (23).

CLA reduced prostaglandin synthesis, especially PGE2 (12) (13), and decreased stearoyl-CoA desaturase activity (14). The trans-10,cis-12 isomer decreased serum HDL cholesterol levels (9), inhibited stearoyl-CoA desaturase activity (12), and decreased insulin-like growth factor-II secretion at both transcriptional and post-transcriptional levels (18).

Laboratory and animal studies suggest that CLA has both anti- and pro-oxidant effects (40) (41). CLA may reduce abdominal adiposity through increased energy expenditure, while myocardial oxidative stress may occur through changes in transmembrane potential or the antioxidant defense system (40).

In humans, CLA appeared to have a synergistic effect with a mixture of oleic and erucic acids in reducing neuroinflammation and enhancing peroxisomal beta-oxidation (42). In human skeletal muscle, CLA enhanced the rate of glycogen resynthesis after exercise (43).

It is thought that replacing other polyunsaturated fatty acids (PUFAs) with CLA may reduce oxidative stress and modulate intracellular signaling (11). These effects may inhibit carcinogenesis and affect cellular responses to tumor necrosis factor-alpha (TNF-alpha) (15). In vitro, CLA inhibited MCF-7 breast cancer cell proliferation, but the mechanisms by which this occurred for both isomers (trans-10,cis-12 and cis-9,trans-11) differed and require future elucidation (3). The cis-9,trans-11 isomer induced tissue inhibitor of metalloproteinase (TIMP)-1 and TIMP-2 mRNA in SGC-7901 human gastric carcinoma cells, which may play a role in inhibiting the tumor metastasis cascade (2). This inhibition may come from blocking the cell cycle with reduced expressions of cyclin A, B1 and D1 and enhanced cyclin-dependent kinase inhibitor (CDKI) expression (17).

In animal models of colorectal cancer, suppression of disease activity was attributed to peroxisome proliferator-activated receptor gamma (PPARy) activation (36). Other possible mechanisms include increased apoptosis and enhanced caspase-3 activity in the colon mucosa (37). Preliminary studies in human breast cancers suggest anticancer effects occurred through suppression of fatty acid synthesis (39). In rectal cancer, CLA supplementation may improve markers of inflammation, and reduce angiogenesis and tumor invasion via matrix metalloproteinase-9 inhibition (38) (44).

The cis-9,trans-11 isomer may modify platelet activation and aggregation, and displayed anticoagulant properties (24).


CLA should be used with caution in patients who have cardiovascular disease or diabetes, as it has increased lipid peroxidation and caused insulin resistance / decreased insulin sensitivity (9) (25) (45).

Adverse Reactions

Fatigue, gastrointestinal symptoms (6) (9).

Herb-Drug Interactions

Anticoagulant/antiplatelet drugs: The cis-9,trans-11 isomer has also been shown to have anticoagulant/antiplatelet activities (24). It may increase the effect of drugs with similar properties.

Dosage (OneMSK Only)
  1. D’Orazio N, Ficoneri C, Riccioni G, Conti P, Theoharides TC, Bollea MR. Conjugated linoleic acid: a functional food? Int J Immunopathol Pharmacol. 2003;16:215-20.

  2. Chen BQ, Yang YM, Gao YH, Liu JR, Xue YB, Wang XL et al. Inhibitory effects of c9, t11-conjugated linoleic acid on invasion of human gastric carcinoma cell line SGC-7901. World J Gastroenterol. 2003;9:1909-14.

  3. Chujo H, Yamasaki M, Nou S, Koyanagi N, Tachibana H, Yamada K. Effect of conjugated linoleic acid isomers on growth factor-induced proliferation of human breast cancer cells. Cancer Lett. 2003;202:81-7.

  4. Ip MM, Masso-Welch PA, Ip C. Prevention of mammary cancer with conjugated linoleic acid: role of the stroma and the epithelium. J Mammary Gland Biol Neoplasia. 2003;8:103-18.

  5. Miner JL, Cederberg CA, Nielsen MK, Chen X, Baile CA. Conjugated linoleic acid (CLA), body fat, and apoptosis. Obes Res. 2001;9:129-34.

  6. Blankson H, Stakkestad JA, Fagertun H, Thom E, Wadstein J, Gudmundsen O. Conjugated linoleic acid reduces body fat mass in overweight and obese humans. J Nutr. 2000;130:2943-8.

  7. Smedman A,.Vessby B. Conjugated linoleic acid supplementation in humans—metabolic effects. Lipids. 2001;36:773-81.

  8. Mougios V, Matsakas A, Petridou A, Ring S, Sagredos A, Melissopoulou A et al. Effect of supplementation with conjugated linoleic acid on human serum lipids and body fat. J Nutr Biochem. 2001;12:585-94.

  9. Pariza MW, Park Y, Cook ME. Mechanisms of action of conjugated linoleic acid: evidence and speculation. Proc Soc Exp Biol Med. 2000;223:8-13.

  10. Pariza MW, Park Y, Cook ME. Conjugated linoleic acid and the control of cancer and obesity. Toxicol Sci. 1999;52:107-10.

  11. Banni S, Angioni E, Casu V, Melis MP, Scrugli S, Carta G et al. An increase in vitamin A status by the feeding of conjugated linoleic acid. Nutr Cancer. 1999;33:53-7.

  12. Liu JR, Li BX, Chen BQ, Han XH, Xue YB, Yang YM et al. Effect of cis-9, trans-11-conjugated linoleic acid on cell cycle of gastric adenocarcinoma cell line (SGC-7901). World J Gastroenterol. 2002;8:224-9.

  13. Cho HJ, Lee HS, Chung CK, Kang YH, Ha YL, Park HS et al. trans-10, cis-12 conjugated linoleic acid reduces insulin-like growth factor-II secretion in HT-29 human colon cancer cells. J Med Food. 2003;6:193-9.

  14. Herbel BK, McGuire MK, McGuire MA, Shultz TD. Safflower oil consumption does not increase plasma conjugated linoleic acid concentrations in humans. Am J Clin Nutr. 1998;67:332-7.

  15. Bassaganya-Riera J, Hontecillas R. Dietary conjugated linoleic acid and n-3 polyunsaturated fatty acids in inflammatory bowel disease. Curr Opin Clin Nutr Metab Care. 2010 Sep;13(5):569-73.

  16. MacRedmond R, Singhera G, Attridge S, et al. Conjugated linoleic acid improves airway hyper-reactivity in overweight mild asthmatics. Clin Exp Allergy. 2010 Jul;40(7):1071-8.

  17. Bachmair EM, Bots ML, Mennen LI, et al. Effect of supplementation with an 80:20 cis9,trans11 conjugated linoleic acid blend on the human platelet proteome. Mol Nutr Food Res. Jul 2012;56(7):1148-1159.

  18. Lopez-Plaza B, Bermejo LM, Koester Weber T, et al. Effects of milk supplementation with conjugated linoleic acid on weight control and body composition in healthy overweight people. Nutr Hosp. Nov-Dec 2013;28(6):2090-2098.

  19. Tajmanesh M, Aryaeian N, Hosseini M, et al. Conjugated Linoleic Acid Supplementation has no Impact on Aerobic Capacity of Healthy Young Men. Lipids. Aug 2015;50(8):805-809.

  20. Jenkins ND, Buckner SL, Baker RB, et al. Effects of 6 weeks of aerobic exercise combined with conjugated linoleic acid on the physical working capacity at fatigue threshold. J Strength Cond Res. Aug 2014;28(8):2127-2135.

  21. Diniz YS, Santos PP, Assalin HB, et al. Conjugated linoleic acid and cardiac health: oxidative stress and energetic metabolism in standard and sucrose-rich diets. Eur J Pharmacol. Jan 28 2008;579(1-3):318-325.

  22. Soel SM, Choi OS, Bang MH, et al. Influence of conjugated linoleic acid isomers on the metastasis of colon cancer cells in vitro and in vivo. J Nutr Biochem. Oct 2007;18(10):650-657.

  23. Basu S, Riserus U, Turpeinen A, et al. Conjugated linoleic acid induces lipid peroxidation in men with abdominal obesity. Clin Sci (Lond). Dec 2000;99(6):511-516.

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