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Nutritional Supplement

Conjugated Linoleic Acid

Possible Deficiencies

No deficiencies of CLA are reported or believed to occur, since it is not an essential nutrient.

Side Effects

Overweight volunteers who took 4.5 grams of CLA per day for one year had an increase in their blood levels of lipoprotein(a), a risk factor for heart disease.24 In a double-blind study of human volunteers, supplementation with 4.2 grams per day of a mixture of cis-9,trans-11 CLA and trans-10,cis-12 CLA for three months increased the concentration of C-reactive protein, another risk factor for heart disease.25 In a study of healthy volunteers, supplementing with 4.5 grams of CLA per day for 12 weeks caused an impairment of blood vessel function (endothelial dysfunction), which is believed to be associated with an increased risk of heart disease.26 Taken together, these findings suggest that long-term use of CLA could increase the risk of developing heart disease.

In a double-blind study of people with type 2 diabetes, supplementing with 3 grams of CLA per day for eight weeks significantly increased blood glucose levels by 6.3% and decreased insulin sensitivity.27 A reduction in insulin sensitivity was also seen in a study of overweight men without diabetes after treatment with 3 grams of CLA per day for three months.28 However, in another study of obese men and women, supplementation with 6 grams of CLA per day for 24 weeks had no significant effect on blood glucose levels or insulin sensitivity.29 Moreover, in a study of young sedentary men, 4 grams of CLA per day for eight weeks improved insulin sensitivity.30 Although the studies are conflicting, it would be prudent for people who have, or are at risk of developing, diabetes to monitor their blood sugar levels during long-term use of CLA. One unpublished human trial reported isolated cases of gastrointestinal upset.31

References

1. Thom E, Wadstein J, Gudmundsen O. Conjugated linoleic acid reduces body fat in healthy exercising humans. J Int Med Res 2001;29:392-6.

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

3. Zambell KL, Keim NL, Van Loan MD, et al. Conjugated linoleic acid supplementation in humans: effects on body composition and energy expenditure. Lipids 2000;35:777-82.

4. Riserus U, Berglund L, Vessby B. Conjugated linoleic acid (CLA) reduced abdominal adipose tissue in obese middle-aged men with signs of the metabolic syndrome: a randomised controlled trial. Int J Obes Relat Metab Disord 2001;25:1129-35.

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

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

7. Whigham LD, Watras AC, Schoeller DA. Efficacy of conjugated linoleic acid for reducing fat mass: a meta-analysis in humans. Am J Clin Nutr 2007;85:1203–11.

8. Kreider RB, Ferreira MP, Greenwood M, et al. Effects of conjugated linoleic acid supplementation during resistance training on body composition, bone density, strength, and selected hematological markers. J Strength Cond Res 2002;16:325-34.

9. West DB, Delany JP, Camet PM, et al. Effects of conjugated linoleic acid on body fat and energy metabolism in the mouse. Am J Physiol 1998;275:R667-72.

10. Park Y, Albright KJ, Liu W, et al. Effect of conjugated linoleic acid on body composition in mice. Lipids 1997;32:853-8.

11. Ferreira M, Krieder R, Wilson M. Effects of CLA supplementation during resistance training on body composition and strength. J Strength Conditioning Res 1998;11:280.

12. Kreider RB, Ferreira MP, Greenwood M, et al. Effects of conjugated linoleic acid supplementation during resistance training on body composition, bone density, strength, and selected hematological markers. J Strength Cond Res 2002;16:325-34.

13. Lowery LM, Appicelli PA, Lemon PWR. Conjugated linoleic acid enhances muscle size and strength gains in novice bodybuilders. Med Sci Sport Excer 1998;30:S182 [abstract]

14. Thom E, Wadstein J, Gudmundsen O. Conjugated linoleic acid reduces body fat in healthy exercising humans. J Int Med Res 2001;29:392-6.

15. Cesano A, Visonneau S, Scimeca JA, et al. Opposite effects of linoleic acid and conjugated linoleic acid on human prostatic cancer in SCID mice. Anticancer Res 1998;18:1429-34.

16. Thompson H, Zhu Z, Banni S, et al. Morphological and biochemical status of the mammary gland as influenced by conjugated linoleic acid: implication for a reduction in mammary cancer risk. Cancer Res 1997;57:5067-72.

17. Ip C. Review of the effects of trans fatty acids, oleic acid, n-3 polyunsaturated fatty acids, and conjugated linoleic acid on mammary carcinogenesis in animals. Am J Clin Nutr 1997;66(suppl):1523S-29S [review].

18. Parodi PW. Cows' milk fat components as potential anticarcinogenic agents. J Nutr 1997;127:1055-60 [review].

19. Cesano A, Visonneau S, Scimeca JA, et al. Opposite effects of linoleic acid and conjugated linoleic acid on human prostatic cancer in SCID mice. Anticancer Res 1998;18:1429-34.

20. Thompson H, Zhu Z, Banni S, et al. Morphological and biochemical status of the mammary gland as influenced by conjugated linoleic acid: implication for a reduction in mammary cancer risk. Cancer Res 1997;57:5067-72.

21. Ip C. Review of the effects of trans fatty acids, oleic acid, n-3 polyunsaturated fatty acids, and conjugated linoleic acid on mammary carcinogenesis in animals. Am J Clin Nutr 1997;66(suppl):1523S-29S [review].

22. Parodi PW. Cows' milk fat components as potential anticarcinogenic agents. J Nutr 1997;127:1055-60 [review].

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

24. Gaullier JM, Halse J, Hoye K, et al. Conjugated linoleic acid supplementation for 1 y reduces body fat mass in healthy overweight humans. Am J Clin Nutr 2004;79:1118–25.

25. Smedman A, Basu S, Jovinge S, Fredrikson GN, Vessby B. Conjugated linoleic acid increased C-reactive protein in human subjects. Br J Nutr 2005;94:791-5.

26. Taylor JS, Williams SR, Rhys R, et al. Conjugated linoleic acid impairs endothelial function. Arterioscler Thromb Vasc Biol2006;26:307-12.

27. Moloney F, Yeow TP, Mullen A, et al. Conjugated linoleic acid supplementation, insulin sensitivity, and lipoprotein metabolism in patients with type 2 diabetes mellitus. Am J Clin Nutr 2004;80:887-95.

28. Riserus U, Vessby B, Arnlov J, Basu S. Effects of cis-9,trans-11 conjugated linoleic acid supplementation on insulin sensitivity, lipid peroxidation, and proinflammatory markers in obese men. Am J Clin Nutr 2004;80:279-83.

29. Whigham LD, O'Shea M, Mohede IC, et al. Safety profile of conjugated linoleic acid in a 12-month trial in obese humans. Food Chem Toxicol 2004 Oct;42(10):1701-9.

30. Eyjolfson V, Spriet LL, Dyck DJ. Conjugated linoleic acid improves insulin sensitivity in young, sedentary humans. Med Sci Sports Exerc 2004;36:814-20.

31. Thom E. A pilot study with the aim of studying the efficacy and tolerability of Tonalin CLA on the body composition in humans. Lillestrom, Norway: Medstat Research Ltd., July 1997 [unpublished].

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The information presented by Healthnotes is for informational purposes only. It is based on scientific studies (human, animal, or in vitro), clinical experience, or traditional usage as cited in each article. The results reported may not necessarily occur in all individuals. For many of the conditions discussed, treatment with prescription or over the counter medication is also available. Consult your doctor, practitioner, and/or pharmacist for any health problem and before using any supplements or before making any changes in prescribed medications. Information expires December 2018.

Copyright © 2018 Healthnotes, Inc. All rights reserved.

The information presented by Healthnotes is for informational purposes only. It is based on scientific studies (human, animal, or in vitro), clinical experience, or traditional usage as cited in each article. The results reported may not necessarily occur in all individuals. Self-treatment is not recommended for life-threatening conditions that require medical treatment under a doctor's care. For many of the conditions discussed, treatment with prescription or over the counter medication is also available. Consult your doctor, practitioner, and/or pharmacist for any health problem and before using any supplements or before making any changes in prescribed medications. Information expires December 2018.