Conjugated Linoleic Acid and Disease Prevention: A Review of Current Knowledge

Abstract

Conjugated linoleic acid (CLA), a derivative of a fatty acid linoleic acid (LA), has been reported to decrease tumorigenesis in animals. CLA is unique because unlike most antioxidants which are components of plant products, it is present in food from animal sources such as dairy foods and meats. CLA concentrations in dairy products typically range from 2.9 to 8.92 mg/g fat of which the 9-cis, 11-trans isomer makes up to 73% to 93% of the total CLA. Low concentrations of CLA are found in human blood and tissues. In vitro results suggest that CLA is cytotoxic to MCF-7 cells and it inhibits the proliferation of human malignant melanoma and colorectal cancer cells. In animal studies, CLA has inhibited the development of mouse epidermal tumors, mouse forestomach cancer and rat mammary cancer. Hamsters fed CLA collectively had significantly reduced levels of plasma total cholesterol, non-high-density lipoprotein cholesterol, (combined very-low and low-density lipoprotein) and triglycerides with no effect on high-density lipoprotein cholesterol, as compared to controls. Dietary CLA modulated certain aspects of the immune defense but had no obvious effect on the growth of an established, aggressive mammary tumor in mice. It is now thought that CLA itself may not have anti-oxidant capabilities but may produce substances which protect cells from the detrimental effects of peroxides.

There is, however, insufficient evidence from human epidemiological data, and very few of the animal studies have shown a dose-response relationship with the quantity of CLA feed and the extent of tumor growth. Further research with tumor models is needed to test the efficacy and utility of CLA in cancer and other disease prevention and form the basis of evaluating its effect in humans by observational studies and clinical trials.

• conjugated linoleic acid
• CLA
• cancer
• heart disease
• antioxidant
• fatty acids

Key teaching points:

• CLA may inhibit the development of tumors through its effect on antioxidants.

• It may also have a role in preventing atherosclerosis and modulate certain aspects of immune system.

• The evidence is primarily based on in vitro and animal studies.

• Further research with tumor models and human epidemiological data is warranted.

Key teaching points:

• CLA may inhibit the development of tumors through its effect on antioxidants.

• It may also have a role in preventing atherosclerosis and modulate certain aspects of immune system.

• The evidence is primarily based on in vitro and animal studies.

• Further research with tumor models and human epidemiological data is warranted.