The Effects of CLA on Health
For the past two decades, conjugated linoleic acid (CLA) has attracted significant research interest due to its favourable potential effects on health. While studies are still in their early phase, published reviews on CLA have highlighted the benefits of this natural ruminant fat.
Various animal and human studies have investigated the role of CLA on health. It has been suggested that the effects of CLA on health arise from interactions between two main isomers: c-9,t-11 CLA and t-10,c-12 CLA. CLA may play an important protective role in:
- Cardiovascular diseases,
- Bone health,
- Immune and inflammatory responses.
For more information: What is CLA?
Emerging evidence suggests that ruminant trans fat is beneficial for cardiovascular health. Results from a number of animal studies indicate that CLA has anti-atherosclerotic properties. It has been found that CLA improves blood lipid profiles by reducing total cholesterol, triacylglyceride and LDL cholesterol levels and improving HDL cholesterol levels.1 However, human studies on CLA and cardiovascular disease markers such as blood lipids and blood pressure have revealed inconsistent findings.
For more information: The Facts on Natural Trans Fat and Cardiovascular Disease
Evidence from the literature suggests that CLA has potential benefits against cancer. Studies examining the consumption of CLA-rich milk products such as cheese have shown an inverse association with breast cancer. One study also found an inverse correlation between CLA intake and colorectal cancer among women. Animal models suggest that the mechanisms of the anti-carcinogenic properties of CLA include modulation of eicosanoid production, interference in cell signaling pathways, inhibition of DNA synthesis, promotion of apoptosis, and modulation of angiogenesis.1
Several studies of CLA supplementation have demonstrated that CLA may have an anti-obesity effect and may improve body composition. In a review article on long-term CLA supplementation in humans, CLA was linked to a modest reduction in body fat and/or the prevention of regaining body fat in overweight or obese subjects.2 Another review examined the mechanistic actions of CLA in obesity, and it was found in some studies on humans that supplementation with CLA reduced adiposity, whereas this effect has been found consistently in all studies on animals. The consistency in the results of animal studies may be due to the higher CLA dosage used in the trials with animal models compared to the dosage used on human subjects.
The potential anti-obesity mechanisms of CLA include appetite suppression and increased energy expenditure through increased basal metabolic rate. Additionally, CLA inhibits adipogenesis and regulates lipogenesis. Another anti-obesity mechanism of CLA is that it induces inflammation to produce pro-inflammatory cytokines called adipokines. These can cause insulin resistance, which in turn suppresses lipid synthesis and increases lipolysis in adipocytes. Furthermore, CLA promotes and regulates adipocyte apoptosis.3
A 2011 narrative review on CLA and bone health concluded that preclinical data support a beneficial effect of CLA on bone health. In fact, it appears that CLA maintains bone mass while inducing weight loss through the modulation of specific nuclear receptors.4
Immune and Inflammatory Response
Various studies using animal models have shown beneficial effects of CLA on immune and inflammatory responses, including:
- reduction of adverse effects caused by immune challenges;
- reduction of colonic inflammation;
- decrease in antigen-induced cytokine production in immune-competent cells;
- reduction of allergic-type immune responses;
- modulation of the production of cytokines, prostaglandins and leukotrienes.
However, current evidence regarding these effects in humans is inconclusive.1
There is consistent evidence from animal studies that CLA may have several beneficial effects on health. However, more research is needed to gain conclusive evidence on the potential protective effect of CLA in humans.
- Dilzer A and Park Y. Implication of conjugated linoleic acid (CLA) in human health. Crit Rev Food Sci Nutr 2012;52(6):488-513.
- Jutzeler van Wijlen RP. Long-term conjugated linoleic acid supplementation in humans – effects on body composition and safety. Eur J Lipid Sci Technol 2011;113(9):1077-94.
- Kennedy A et al. Antiobesity mechanisms of action of conjugated linoleic acid. J Nutr Biochem 2010;21(3):171-9.
- Ing SW and Belury MA. Impact of conjugated linoleic acid on bone physiology: proposed mechanism involving inhibition of adipogenesis. Nutr Rev 2011;69(3):123-31.