What is CLA?
Conjugated Linoleic Acid (CLA) refers to a group of naturally occurring isomers of linoleic acid present in ruminant fats and dairy products. Unlike industrial trans fatty acids, trans CLA may be of great potential benefit to human health.
CLA isomers are produced from the biohydrogenation of linoleic acid by rumen bacteria of animals. The isomers that contain a double bond in the trans configuration are biologically active.1 CLA has been shown to offer numerous health benefits with respect to cardiovascular disease, cancer, obesity, osteoporosis and the immune system.
For more information, read The Impact of CLA.
Dairy products are the richest source of CLA, providing about 70% of total dietary CLA, compared to 25% from beef and smaller amounts from other ruminants.2
Moreover, as much as 40% of the trans in Canadian dairy fat is vaccenic acid (an isomer of oleic acid), at least 20% of which is converted into CLA in the human body.3-4 In contrast, elaidic acid, which is the industrial trans isomer of oleic acid and the dominant industrial trans fatty acid, is not converted into CLA and has been shown to have adverse effects on cardiovascular health.
The most studied bioactive CLAs are the cis-9,trans-11 isomer (c-9,t-11 CLA, also known as rumenic acid) and the trans-10,cis-12 isomer (t-10,c12 CLA). The cis-9,trans-11 isomer is the predominant isomer in foods, accounting for up to 90% of total CLA found in dairy products and ruminant meats. The trans-10,cis-12 isomer comprises 5% or less of total CLA.5
Structural differences between non-conjugated and conjugated double bonds in a polyunsaturated fatty acid:
Structural differences between cis and trans double bonds in an unsaturated fatty acid:
Structures of linoleic acid (top), c-9,t-11 CLA (middle) and t-10,c12 CLA (bottom):
- Churruca I et al. Conjugated linoleic acid isomers: differences in metabolism and biological effects. Biofactors 2009;35(1):105-11.
- Lock AL et al. The biology of trans fatty acids: implications for human health and the dairy industry. Aust J Dairy Technol 2005;60(2):3-12.
- Turpeinen AM et al. Bioconversion of vaccenic acid to conjugated linoleic acid in humans. Am J Clin Nutr 2002;76(3):504-10.
- Mendis S et al. Fatty acid profile of Canadian dairy products with special attention to the trans-octadecenoic acid and conjugated linoleic acid isomers. J AOAC Int 2008;91(4):811-9.
- Crumb DJ. Conjugated linoleic acid (CLA) – an overview. Int J Applied Res Nat Prod 2011;4(3):12-8.
Keywords: conjugated linoleic acid