Conjugated linoleic acid as a therapeutic supplement
Conjugated linoleic acid (CLA) is a natural fatty acid found in foods, particularly in animal products like kangaroo meat, and is often marketed as a dietary supplement for various health benefits. It is primarily promoted for its potential to improve body composition and aid in weight loss, although research on its efficacy is mixed. Some studies suggest that CLA might have a minimal effect on reducing body fat; however, there are concerns that it could negatively impact insulin sensitivity, particularly in overweight individuals, thereby increasing the risk of diabetes.
Moreover, CLA has been explored for additional uses, including potential benefits for allergic rhinitis, cancer prevention, diabetes management, and high cholesterol. While some animal studies indicate promising results regarding cardiovascular health and anti-obesity effects, human clinical research remains inconclusive and highlights the need for further investigation. It is important for consumers to approach CLA supplementation cautiously, particularly individuals with diabetes, pregnant or nursing women, and those with liver or kidney issues, as safety and dosage guidelines are still not well established. Overall, while CLA is often considered for therapeutic use, an informed approach is necessary due to varying evidence of its benefits and potential risks.
Conjugated linoleic acid as a therapeutic supplement
- DEFINITION: Natural substance of the human body used as a supplement to treat specific health conditions.
- PRINCIPAL PROPOSED USE: Improving body composition and weight loss
- OTHER PROPOSED USES: Allergic rhinitis, cancer prevention, diabetes, high cholesterol, metabolic syndrome
Overview
Conjugated linoleic acid (CLA) is a mixture of different isomers, or chemical forms, of linoleic acid. Linoleic acid is an essential fatty acid, a type of fat that the body needs for optimum health.
Based on preliminary evidence, CLA has been promoted as a fat-burning supplement and as a treatment for diabetes. However, there is little evidence that it works and growing evidence that CLA might actually worsen blood sugar control in people who are overweight.
Requirements and Sources
Although linoleic acid is an important nutritional source of essential fatty acids, there is no evidence that people need to get conjugated linoleic acid in their diet. CLA does occur in food, but it would be very difficult to get the recommended dose that way. Supplements are the only practical source.
Therapeutic Dosages
The typical dosage of CLA ranges from 3 to 5 g daily. As with all supplements taken at this high a dosage, it is important to purchase a reputable brand, as even very small amounts of a toxic contaminant could quickly add up.
Therapeutic Uses
While CLA is often recommended for aiding weight loss or improving body composition (ratio of muscle to fat), evidence from studies is conflicting. One meta-analysis (systematic statistical review) of all the data found minimal benefits at most. Another meta-analysis concluded that, when taken at a dose of 3.2 grams (g) per day, CLA slightly reduces body fat levels. Finally, in one study, a combination of CLA and chromium failed to improve body composition.
It should be noted that some, but not all, studies have raised concerns that the use of CLA by overweight people could raise insulin resistance and, therefore, increase the risk of diabetes. In addition, its use might increase a person’s cardiovascular risk in other ways, as described in the following Safety Issues section.
One study failed to find that CLA-enriched milk is helpful for metabolic syndrome, a condition associated with an increased risk of heart disease. Another study failed to find that CLA can enhance immune function.
A twelve-week double-blind, placebo-controlled study of forty subjects tested CLA as a treatment for people with allergies to birch pollen (a common cause of hay fever) and found some evidence of benefit. A small double-blind trial found weak evidence that CLA might be useful for high cholesterol. Some animal and test-tube studies suggest that CLA might help prevent cancer, but the evidence is preliminary and inconsistent.
As studies continued into the twenty-first century, it was clear CLA had anti-obesogenic and anti-atherosclerotic properties. A review of studies did show CLA promoted modest weight loss; however, researchers were looking into what role that could play in diabetes prevention. Animal studies clearly showed CLA had the ability to prevent cardiovascular disease, but more human clinical study was necessary. Dosage played a pivotal role in the safety of CLA supplementation.
Safety Issues
CLA appears to be a generally safe nutritional substance. However, there are some concerns with its use. During the course of investigations into its effect on fat, CLA was found to act somewhat similarly to some oral medications used for diabetes. This led to research into the possible usefulness of CLA as a treatment for diabetes. In one study, CLA reduced blood sugar levels in diabetic rats as effectively as a standard diabetes treatment. The same researchers also performed a small double-blind, placebo-controlled trial in humans. The results indicated that CLA improved insulin responsiveness in people with type 2 (adult onset) diabetes. However, several subsequent studies found opposite and rather alarming results: use of CLA by people with diabetes may worsen blood sugar control; in overweight people without diabetes, CLA might decrease insulin sensitivity, creating a prediabetic state. In contrast, a study using the most precise method of measuring insulin sensitivity failed to find any harmful effect. Nonetheless, at present, individuals with diabetes or who are at risk for it should not use CLA except under a physician’s supervision.
One study found that CLA impairs endothelial function and another that it increases levels of C-reactive protein; both of these effects suggest a possible increase in cardiovascular risk.
Concerns have also been raised regarding the use of CLA by nursing mothers. A double-blind, placebo-controlled study indicates that the use of CLA reduces the fat content of human breast milk. Since infants depend on the fat in breast milk to provide adequate calories and on certain fats to aid proper growth and development, it is probably prudent for nursing mothers to avoid CLA supplements. Maximum safe dosages of CLA for young children, pregnant women, and those with severe liver or kidney disease have not been determined.
Bibliography
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