Introduction

Conjugated linoleic acid (CLA) refers to a group of positional and geometric octadecadienoic acid isomers of linoleic acid. Unlike linoleic acid, all CLA isomers have conjugated double bonds (two double bonds separated by a single bond). CLA is not a single substance but comprises 28 positional and geometrical isomers, of which only 9cis,11trans and 10trans,12cis have thus far been proven to possess significant biological activities.¹

CLA is found predominantly in organic milk fat from free-range, grass-fed cows. Research has demonstrated CLA’s favorable impact on several biological processes, particularly carcinogenesis, body composition, and metabolism.²

CLA content in cheese directly correlates with CLA levels in milk, as these bioactive lipids transfer from milk to cheese during production. The CLA concentration in milk can be enhanced through feed enriched with α-linolenic and linoleic acids, including pasture grass, plant oils, oil-rich cereals, and fish oils. While previous reviews from the last decade suggested CLA levels remained stable during cheese ripening, current research demonstrates that specific probiotic bacteria—namely Lactiplantibacillus plantarum, Lactobacillus acidophilus, Lacticaseibacillus casei, and Bifidobacterium lactis—can significantly increase CLA levels by converting linoleic acid throughout the ripening process. These bacterial starters elevated CLA concentrations by factors of 1.19, 1.6, and 6.6 times compared to controls in Ovine model, Miniature, and Cheddar cheese varieties, respectively. However, it should be noted that CLA levels can decrease during storage due to lipid oxidation triggered by environmental factors such as exposure to fluorescent light or aerobic conditions.³

Actions and Pharmacology

CLA demonstrates multiple beneficial activities in humans, including:

• Anti-carcinogenic effects
• Anti-atherogenic properties
• Anti-diabetogenic actions
• Body composition-modifying activities

These activities have been well-documented in experimental animal models.⁴

Evidence-Based Benefits

Body Composition

• Reduces body fat mass while preserving lean muscle tissue
• Meta-analysis of 18 human studies confirms modest but significant fat reduction at 3.2g/day⁵
• A randomized, double-blind study with 60 overweight/obese volunteers found significantly greater reduction in body fat mass with CLA supplementation⁶
• Works through multiple mechanisms including increased energy expenditure and decreased fat storage⁷

Metabolic Effects

• Improves insulin sensitivity in type 2 diabetics
• Reduces blood glucose, serum triglycerides, and cholesterol levels
• Clinical trial with 54 obese adults showed 3000mg daily CLA for 3 months significantly decreased fasting plasma glucose and improved insulin resistance markers⁸
• Activates PPAR-gamma receptors, enhancing glucose regulation⁹

Anti-Cancer Properties

• Inhibits multiple types of cancer cells including breast, colon, and gastric cancers
• Epidemiological evidence: women consuming ≥4 servings of high-fat dairy foods daily had 41% lower risk of bowel cancer than those consuming 
• CLA inhibits peritoneal metastasis in human gastric and colon cancer cells, improving survival rates in animal models¹⁰
• The breast cancer-inhibitory effects of CLA work through multiple mechanisms including decreased production of 5-HETE and reduced angiogenesis¹¹

Anti-Inflammatory Effects

• Decreases production of pro-inflammatory cytokines and eicosanoids
• Reduces TNF-alpha, IL-6, and other inflammatory markers¹²
• Dietary CLA decreased cachexia (muscle wasting) and modulated macrophage TNF-alpha production in experimental models¹³

Clinical Applications

• Effective dose ranges from 3-7g daily
• Different isomers may produce varying effects
• Systematic review of human studies shows greater benefits with consistent supplementation over 12+ weeks¹⁴
• May be particularly beneficial for metabolic syndrome, obesity, and cancer prevention^15-17

References

1. Banni S. (2002). Conjugated linoleic acid metabolism. Current Opinion in Lipidology, 13(3):261-6.
2. Govari M, Vareltzis P. Conjugated linoleic acid in cheese: A review of the factors affecting its presence. J Food Sci. 2025 Feb;90(2):e70021. doi: 10.1111/1750-3841.70021. PMID: 39898990; PMCID: PMC11789828.
3. Govari M, Vareltzis P. Conjugated linoleic acid in cheese: A review of the factors affecting its presence. J Food Sci. 2025 Feb;90(2):e70021. doi: 10.1111/1750-3841.70021. PMID: 39898990; PMCID: PMC11789828.
4. Govari M, Vareltzis P. Conjugated linoleic acid in cheese: A review of the factors affecting its presence. J Food Sci. 2025 Feb;90(2):e70021. doi: 10.1111/1750-3841.70021. PMID: 39898990; PMCID: PMC11789828.
5. Whigham LD, Watras AC, Schoeller DA. (2007). Efficacy of conjugated linoleic acid for reducing fat mass: a meta-analysis in humans. American Journal of Clinical Nutrition, 85(5):1203-11.
6. Blankson H, Stakkestad JA, Fagertun H, et al. (2000). Conjugated linoleic acid reduces body fat mass in overweight and obese humans. Journal of Nutrition, 130(12):2943-8.
7. Corl BA, Mathews Oliver SA, Lin X, et al. (2008). Conjugated linoleic acid reduces body fat accretion and lipogenic gene expression in neonatal pigs fed low- or high-fat formulas. Journal of Nutrition, 138(3):449-54.
8. Esmaeili Shahmirzadi F, Ghavamzadeh S, Zamani T. (2019). The Effect of Conjugated Linoleic Acid Supplementation on Body Composition, Serum Insulin and Leptin in Obese Adults. Archives of Iranian Medicine, 22(5):255-261.
9. Zhou X, Sun C, Jiang L, Wang H. (2004). Effect of conjugated linoleic acid on PPAR gamma gene expression and serum leptin in obese rats. Wei Sheng Yan Jiu, 33(3):307-9.
10. Kuniyasu H, Yoshida K, Sasaki T, et al. (2006). Conjugated linoleic acid inhibits peritoneal metastasis in human gastrointestinal cancer cells. International Journal of Cancer, 118(3):571-576.
11. Kim JH, Hubbard NE, Ziboh V, Erickson KL. (2005). Attenuation of breast tumor cell growth by conjugated linoleic acid via inhibition of 5-lipoxygenase activating protein. Biochimica et Biophysica Acta, 1736(3):244-50.
12. Yu Y, Correll PH, Vanden Heuvel JP. (2002). Conjugated linoleic acid decreases production of pro-inflammatory products in macrophages: evidence for a PPAR gamma-dependent mechanism. Biochimica et Biophysica Acta, 1581(3):89-99.
13. Yang M, Cook ME. (2003). Dietary conjugated linoleic acid decreased cachexia, macrophage tumor necrosis factor-alpha production, and modifies splenocyte cytokines production. Experimental Biology and Medicine, 228(1):51-8.
14. Salas-Salvado J, Marquez-Sandoval F, Bullo M. (2006). Conjugated linoleic acid intake in humans: a systematic review focusing on its effect on body composition, glucose, and lipid metabolism. Critical Reviews in Food Science and Nutrition, 46(6):479-88.
15. Joyal SV. (2004). A perspective on the current strategies for the treatment of obesity. Current Drug Targets CNS and Neurological Disorders, 3(5):341-56.
16. Toomey S, McMonagle J, Roche HM. (2006). Conjugated linoleic acid: a functional nutrient in the different pathophysiological components of the metabolic syndrome? Current Opinion in Clinical Nutrition and Metabolic Care, 9(6):740-7.
17. Terpstra AH, Beynen AC, Everts H, et al. (2002). The decrease in body fat in mice fed conjugated linoleic acid is due to increases in energy expenditure and energy loss in the excreta. Journal of Nutrition, 132(5):940-5.