The health benefits of cutting down on dietary saturated fatty acids and including higher levels of unsaturated fatty acids are well documented. Nutritional research is focusing on the effects of incorporating these healthier fatty acids, such as conjugated linoleic acid (CLA), into animal and human diets. CLA is present in dairy products and meat from ruminants and in very low amounts in our bodies.
Health benefits of conjugated linoleic acid (CLA)
Dr Helen Roche, a senior lecturer in molecular nutrition in Trinity College Dublin, has been studying CLA and its biological properties for several years. "CLA seems to protect cells programmed to become diabetic against development of diabetes and it also prevents disease processes that lead to atherosclerosis, chronic inflammation and colon cancer," says Dr Roche.
Classified as a nutraceutical or nutritional supplement, CLA is thought to change the balance between fat cells and muscle cells in the body and is currently on sale in health shops as a supplement to help people improve their body tone.
"The problem is that commercially available supplements contain two forms of the compound known as isomers," explains Dr Paul Evans, a researcher with the Centre for Synthesis and Chemical Biology (CSCB). "Isomers are molecules that have the same molecular formula but the atoms are arranged differently in space. In the case of CLA one isomer known as cis-9-trans-11 CLA has beneficial effects but the other form, trans-10-cis-12 CLA, can be detrimental and could induce a diabetic state."
Discovering a selective way to synthesise the beneficial CLA isomer
Dr Evans and his group while working at the School of Chemistry in Trinity College Dublin discovered a way to selectively synthesise the beneficial cis-9-trans-11 CLA in large quantities.
During the CLA project the group also found a method for making trans-vaccenic acid (TVA), the precursor to CLA. Evidence suggests that TVA is converted into CLA by an enzyme in the bovine mammary gland and muscle and by a bacterial enzyme in the human intestine.
"Now that we have a supply of the beneficial form of CLA and TVA we can carry out nutritional studies to determine whether the health effects ascribed to CLA are due to the fatty acid alone or attributable to the metabolic conversion of TVA into CLA," says Dr Roche.
Studying the benefits of trans vaccenic acid (TVA) in livestock
Teagasc have also conducted studies to increase the concentration of CLA in livestock. In a feeding trial conducted in Moorepark they reported that in grazing situations where the levels of CLA were already high in milk fat, they could be increased further by supplementing pasture diets with full fat rapeseeds and soybeans, which are both good sources of unsaturated fatty acids.2
A Teagasc research group led by Dr Aidan Moloney in County Meath has now turned their attention to studying the conversion of TVA into CLA by livestock as this metabolic process may hold the key to explaining some of the benefits of CLA. The study aims to demonstrate the beneficial effects of CLA from beef as well as from chemically synthesised CLA.
"TVA is produced by cattle during digestion of unsaturated fatty acids. We are trying to increase TVA, and to understand how it is converted to CLA in muscle," explains Dr Moloney. "We want to investigate whether increasing TVA by manipulation of the diet of cattle will result in healthier animals and in turn produce higher quality meat and dairy products for the consumer."
The new synthetic methods have enabled the preparation of multi-gram quantities of these biologically important fatty acids.
"This collaborative approach paves the way for developing a pure nutraceutical which could be incorporated into our diet to help protect us against heart disease and diabetes," concludes Dr Evans.
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