Supplement Edge - CLA: Control Body Fat, Enhance Immunity
Monica Brant’s beautiful physique is a product of excellent genetics, long-term training, sound nutrition and a committed attitude. Clearly, these factors cannot be replaced by the use of sports supplements. However, scientific study has identified a number of products that offer true benefits to performance (e.g., creatine) or the achievement of nutritional goals (e.g., meal replacement products). Nevertheless, I must emphasize the point that these supplements should be used as an adjunct to an otherwise balanced nutritional plan, not as a substitute.
Even where a supplement does not produce a true physiological effect, a person might attain some benefit because of a psychological boost or “placebo effect.” The placebo effect describes a favorable outcome arising simply from an individual’s belief that she has received a beneficial treatment. That’s why FitnessRx provides only scientific information on dietary supplements based on placebo-controlled studies published in the leading peer-reviewed scientific journals. We are not interested in anecdotal stories or opinions of so-called fitness gurus. With that said, this article examines some science behind conjugated linoleic acid (CLA).
What is CLA?
The major dietary source of CLA for humans is ruminant meats, such as beef and lamb, and dairy products, such as milk and cheese. However, CLA supplements currently sold are derived from sunflower oil. The published animal studies and clinical trials indicate the possibility that CLA supplementation could be useful in improving human health in a number of areas (Table 1), in particular the reduction of body fat gain, immune enhancement against viral antigens, and improvement in blood lipids.
One-Year Effect of CLA
The objective of a well-controlled study by Dr. J.M. Gaullier and colleagues at Scandinavian Clinical Research in Norway was to ascertain the one-year effect of CLA on body composition and safety in healthy overweight adults consuming an ad libitum (self-directed) diet.2 A total of 180 male and female volunteers with body mass indexes of 25-30 were included in a double-blind, placebo-controlled study. Subjects were randomly assigned to one of three groups: 1) CLA-free fatty acid; 2) CLA-triacylglycerol; or 3) placebo (substance provided in a form identical to the genuine supplements; in this case, olive oil capsules).
Results indicated that the mean body fat mass in the CLA groups was lower than that in the placebo group. Further, subjects receiving CLA-free fatty acid had greater lean body mass than subjects receiving placebo. Finally, adverse events (side effects) did not differ significantly between groups. The authors concluded that long-term supplementation with CLA reduces body fat mass in healthy overweight adults.
Latest CLA study
Recently, Dr. C. Pinkoski and co-workers at the University of Saskatchewan in Canada examined the effects of CLA supplementation during a strength-training program.3 In this study, 77 young male and female subjects were randomized to receive either five grams per day of CLA or placebo for seven weeks. They simultaneously participated in a strength-training program. Following the initial seven weeks, 17 subjects (eight males, nine females) volunteered to cross over to the opposite group for an additional seven weeks of supplementation and training.
For the initial seven weeks, subjects in the CLA group had greater increases in lean tissue mass, greater losses of fat mass and greater increases in resting metabolic rate compared to the placebo group. The difference in resting metabolic rate disappeared when corrected for changes in lean tissue mass. Further, subjects who participated in the crossover study had a greater loss of fat mass and greater increase in biceps muscle thickness while on CLA compared to placebo. The authors concluded, “Supplementation with CLA during strength training increases lean tissue mass and decreases fat mass. The increase in lean tissue mass results in an elevated resting metabolic rate.”
Bottom Line
The recent studies indicate the possibility that CLA supplementation could be useful in improving human health in a number of areas, e.g., controlling body fat gain and enhancing immunity. Evidence for efficacy and safety of CLA supplementation is being steadily strengthened by the results from clinical trials.
Websites of Interest
The International Society of Sports Nutrition (ISSN) is dedicated to promoting and supporting the study, practice, education, research and development of sports nutrition and the sports nutrition profession. All information disseminated by the ISSN is unbiased and scientifically supported. For more information, visit www.sportsnutritionsociety.org.
Nutrition & Metabolism is a brand new open-access, peer-reviewed scientific journal soon to be launched by BioMed Central, an independent publishing house. It will encompass all aspects of nutritional biochemistry, including dietary supplements and weight loss diets. For more information, visit www.nutritionandmetabolism.com.
