All About Conjugated Linoleic Acid (CLA, Tonalin®)

Published: 13th April 2008
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What is conjugated linoleic acid?

In scientific terms, conjugated linoleic acid, or CLA, refers to the conjugated dienoic isomers of linoleic acid, an omega-6 fatty acid essential to good nutrition. In lay terms, CLA is a trans-fat which occurs naturally in ruminant animals that chew their cud, such as cattle and sheep. CLA is not produced in the human body and is available only through diet and nutritional supplements.

Other names for conjugated linoleic acid include CLA-free fatty acid, CLA-Triacylglycerol, LA, linoleic acid and Tonalin®, a synthesized version of conjugated linoleic acid contained in certain CLA dietary supplements.

Sources of CLA

Food sources of CLA include beef and lamb, and dairy products such as milk, cheese and butter. Conjugated linoleic acid also occurs in bison, deer, buffalo and goats. Levels of CLA vary among animal sources and research indicates that grass-fed livestock may contain higher levels of CLA than those fed grain or fodder.

Conjugated linoleic acid supplements such as Tonalin® and others are synthetically engineered by exposing safflower, sunflower and soybean oils (rich in linoleic acid) to base compounds and heat, resulting in a concentrated form of CLA superior to most food sources, say nutritionists.

CLA benefits and claims

There's a lot of buzz among researchers and the media regarding the benefits of Tonalin® and CLA supplements in aiding weight management. Supplement companies claim that conjugated linoleic acid can help individuals lose weight and keep it off. Although this may be the case, and more than two decades of research confirms that CLA modulates the body fat and lean muscle production of animals, studies targeted at weight loss in humans remain inconclusive. Currently, CLA and Tonalin® are the focus of research for their potential in:

• Modulating the immune system and regulating blood lipids

• Boosting metabolic rate

• Decreasing abdominal fat

• Enhancing muscle growth

• Balancing cholesterol and triglyceride counts

• Maintaining healthy insulin levels

• Fighting free radicals (CLA is considered by many to have antioxidant potential)

Consumers may be under the impression that CLA and Tonalin® supplements are effective weight loss solutions backed by science. It's important to keep in mind, however, that the efficacy of these supplements remains unsubstantiated.

Tonalin® and CLA side effects, safety and toxicity

CLA supplementation is said to be relatively safe. Common side effects reported in clinical studies include gastrointestinal upset, diarrhea, loose stools, nausea and dyspepsia. Fatigue has been reported in some cases.

Certain studies indicate that Tonalin® and CLA supplementation might worsen insulin resistance and increase markers of inflammation. Findings are inconsistent and vary among CLA types.

Clinical studies and CLA research

Research conducted in the U.S. and abroad has shown promise for CLA's role in weight loss. Studies conducted on humans have exhibited changes in body fat and lean muscle, but most have failed to isolate CLA as the compound solely responsible for weight loss in test subjects. The diet, exercise regimen and body fat composition and metabolism of study participants in almost all studies have been inconsistent and findings inconclusive.

Tonalin efficacy and the FDA

Although not approved by the FDA, Tonalin and other CLA supplements are Generally Recognized as Safe (GRAS) by the agency. Notwithstanding GRAS, the strength, consistency and effectiveness of Tonalin® and CLA supplements remain questionable among brands.

For more information on Tonalin and CLA, visit


1. Study finds CLA helps trim body fat, but are supplements safe? Environmental Nutrition. July 2007 v30 i7 p3.

2. Mixed results from animal studies of CLA. Pharma Marketletter. March 5, 2007 p0.

3. CLA makes animals stronger, leaner, healthier; how about you? Environmental Nutrition. Feb 2006 v29 i2 p7.

4. Safety of CLA in long-term body fat reduction confirmed in landmark study. Pharma Marketletter. May 30, 2005 p0.

5. CLA all the way. Jim Stoppani. Joe Weider's Muscle & Fitness. Oct 2006 v67 i10 p246 (2).

6. CLA Weight Loss and Other Benefits of Conjugated Linoleic Acid. By: Kiefer, Dale. Life Extension, Jun2005, Vol. 11 Issue 6, p80-87, 8p; (AN 16987426)

7. Conjugated Linoleic Acid. Natural Medicines Comprehensive Database. 2007.

8. Health Benefits of Conjugated Linoleic Acid. Dr. Joseph Mercola. Take Control of Your Health.

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