Conjugated Linoleic Acid for Sports & Fitness

Also known as: CLA

What does it do?

Conjugated linoleic acid (CLA) is a slightly altered form of the essential fatty acid linoleic acid.

Where is it found?

CLA is found mainly in dairy products and also in beef and poultry, eggs, and corn oil. Bacteria that live in the intestine of humans can produce CLA from linoleic acid, but supplementation of a rich source of linoleic acid did not produce increases in blood levels of CLA in one human study.1 CLA is available as a supplement.

Why do athletes use it?*

Some athletes say that CLA

What do the advocates say?*

Research suggests that conjugated linoleic acid (CLA) may help reduce body fat and increase muscle strength and size. There are at least seven human studies (two double-blind and some controlled) showing significant reduction of abdominal obesity and body fat mass in overweight and moderately obese people. However, since most of the studies involved a small number of participants and were short in duration, larger double-blind studies are needed to further document the benefits and mechanisms of action.

Although CLA promotes weight loss, which is good for heart health, it is important to monitor HDL (“good”) cholesterol levels as CLA may reduce them.

How much is usually taken by athletes?

CLA is a slightly altered form of the essential fatty acid linoleic acid. Animal research suggests an effect of CLA supplementation on reducing body fat.2 3 Controlled human research has reported that 5.6 to 7.2 grams per day of CLA produces only non-significant gains in muscle size and strength in experienced and inexperienced weight-training men.4 5 6 A double-blind study of a group of trained men and women reported reduced body fat in the upper arm after 12 weeks of supplementation with 1.8 grams per day of CLA.7 Further research using more accurate techniques for measuring body composition is needed to confirm these findings.

Are there any side effects or interactions?

The side effects of CLA are unknown, due to the limited research in humans. However, one unpublished human trial reported isolated cases of gastrointestinal upset.8

At the time of writing, there were no well-known drug interactions with conjugated linoleic acid.

Resources

See a list of books, periodicals, and other resources for this and related topics.

*Athletes and fitness advocates may claim benefits for CLA based on their personal or professional experience. These are individual opinions and testimonials that may or may not be supported by controlled clinical studies or published scientific articles on CLA. For more complete and detailed information, including references and safety information, see CLA as a nutritional supplement.

References

1. 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.

2. 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.

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

4. 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.

5. 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.

6. 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]

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

8. 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].