PhytoScience - Article

CLA (Conjugated Linoleic Acid)

 

CLA was discovered in 1978 by Michael W. Pariza at the University of Wisconsin while looking for mutagen formations in meat during cooking. CLA occurs naturally in foods such as milk, cheese, beef, and lamb as well as many processed foods. However, getting enough CLA from your diet for the preferred benefit would require considerable intake of these types of foods. This is not only impractical, but would also have a seriously negative impact on your metabolism due to the high caloric penalty you would pay.

CLA is the name for a group of compounds, not all CLA is the same. CLA consists of a group of dienoic isomers of linoleic acid not all of which have active properties. Cooking or heating seems to increase rather than decrease CLA content in foods. The trans-10, cis-12 isomer is metabolized more rapidly than the cis-9, trans-11 isomer. Although CLA may be generated from linoleic acid (LA) by intestinal microorganisms, consumption of excess LA does not appear to increase CLA concentrations in humans. Studies have found large variations in the trans-isomer composition of CLA, the important cis-9, trans-11 isomer may be as little as 73 % to over 90% of the total CLA.

Since CLA has been shown to reduce body fat it is likely that this will be the main reason for supplementation. Human studies have supported evidence from animal studies to show that supplementation with as little as 3.2g of CLA per day can significantly reduce body fat mass in overweight and obese humans. (Blankson et al 2000) There is speculation that the low levels of CLA in a modern diet may be a contributory factor to high levels of obesity reported in Western Societies. It is easy to see that shortages of CLA may occur in a western diet when you consider the different CLA levels in the milk of cows that are intensively farmed as opposed to pasture fed.

CLA is research proven to build muscle, reduce body fat, and induce an optimum cellular environment for improved health! For general health benefits CLA supplementation of 2-3g per day seems appropriate but those looking for a positive effect on body composition should take 3-6g daily. CLA is a natural food constituent, it is well tolerated and is not a stimulant.

Proported Uses

  • Cancer prevention
  • Cancer treatment
  • High cholesterol
  • Weight maintenance
  • Cardio protective

Mechanism of Action

CLA is a strong antioxidant and is readily incorporated into cell membrane phospholipids. It is thought that replacing other PUFAs with CLA may reduce oxidative stress and modulate intracellular signaling. These effects may inhibit carcinogenesis. CLA has been shown to reduce the synthesis of prostaglandins, especially PGE2 and decrease stearoyl-CoA desaturase activity. It may affect cellular response to tumor necrosis factor-alpha (TNF-alpha).

In vitro studies have shown that it inhibits the proliferation of MCF-7 breast cancer cells. CLA supplementation increases liver stores of vitamin A in mice. The role of this effect on carcinogenesis remains unclear. CLA was also shown to cause apoptosis in white adipose tissue in mice.

The two major isomers of CLA, trans-10, cis-12 (t10c12) and cis-9, trans-11 (c9t11), have different physiological properties. The cis-9, trans-11 isomer, the principal dietary form, was shown to induce tissue inhibitor of metalloproteinase mRNA in SGC-7901 human gastric carcinoma cells. This may play a role in inhibiting the tumor metastasis cascade. The inhibition was thought to come from blocking of the cell cycle with reduced expressions of cyclin A, B1 and D1 and enhanced expressions of CDKI. However, the trans-10, cis-12 isomer has been shown to decrease serum HDL cholesterol levels, inhibit the activity of stearoyl-CoA desaturase, inhibit insulin sensitive in new adipose cells and decrease Insulin-Like Growth Factor-II secretion at both transcriptional and post-transcriptional levels

Adverse Reactions

Reported: none

Interactions

CLA may increase insulin resistance causing increase in blood glucose level. CLA may affect cholesterol levels as well as decrease creatinine, bilirubin, creatine-phosphokinase and platelets. CLA may increase potassium levels

Clinical Summary

A group of polyunsaturated fatty acids (PUFA). Conjugated Linoleic Acid (CLA) is commonly found in diary products and beef. This substance has purported benefits for cancer prevention, weight control, and high cholesterol. Animal studies have suggested that CLA may play a role in reducing tumor proliferation in certain cancer cell lines. CLA was shown to cause apoptosis in white adipose tissue in mice.

Human studies of CLA and weight reduction are mixed. Studies of CLA in obese men showed a reduction in body fat mass and body mass index. CLA showed little effect on body composition in non-obese women and healthy adults. In addition, possible insulin resistance, reduction in glycemia and plasma leptin were also observed after supplementation. CLA may affect total cholesterol levels. CLA does not significantly reduce proteolysis in muscles. Reported adverse events include minor gastrointestinal symptoms and one case of severe fatigue

References

  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. Petridou A, Mougios V, Sagredos A. Supplementation with CLA: isomer incorporation into serum lipids and effect on body fat of women. Lipids 2003;38:805-11.
  8. Smedman A,.Vessby B. Conjugated linoleic acid supplementation in humans--metabolic effects. Lipids 2001;36:773-81.
  9. Riserus U, Arner P, Brismar K, Vessby B. Treatment with dietary trans10cis12 conjugated linoleic acid causes isomer-specific insulin resistance in obese men with the metabolic syndrome. Diabetes Care 2002;25:1516-21.
  10. 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.
  11. Belury MA. Conjugated dienoic linoleate: a polyunsaturated fatty acid with unique chemoprotective properties. Nutr Rev. 1995;53:83-9.
  12. 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.
  13. Ma DW, Field CJ, Clandinin MT. An enriched mixture of trans-10,cis-12-CLA inhibits linoleic acid metabolism and PGE2 synthesis in MDA-MB-231 cells. Nutr Cancer 2002;44:203-12.
  14. Choi Y, Park Y, Storkson JM, Pariza MW, Ntambi JM. Inhibition of stearoyl-CoA desaturase activity by the cis-9,trans-11 isomer and the trans-10,cis-12 isomer of conjugated linoleic acid in MDA-MB-231 and MCF-7 human breast cancer cells. Biochem.Biophys.Res Commun. 2002;294:785-90.
  15. Pariza MW, Park Y, Cook ME. Conjugated linoleic acid and the control of cancer and obesity. Toxicol.Sci. 1999;52:107-10.
  16. 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.
  17. 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.
  18. 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.
  19. 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.

Disclaimer:
These statements have not been evaluated by the FDA. Any product mentioned is not intended to diagnose, treat, cure or prevent any disease.