Functional foods may limit cancer

Some foods can do more than simply nourish. A scientist at Teagasc's Moorepark research centre in Co Cork is studying a substance found in milk and beef that can help slow the spread of certain cancers.

"Functional foods" is the name given to products that promise to deliver health benefits, potentially allowing us to eat ourselves well. Dr Catherine Stanton at Moorepark Food Research Centre is an expert in the study of functional foods. She leads an international research consortium looking in particular at one such functional food substance, conjugated linoleic acid (CLA).

"The main focus of my research is to look at dairy products and bioactive components within dairy foods that have been shown to have a health benefit," explains Stanton. "CLA is a bioactive fatty acid naturally found in milk that has anticancer, immune strengthening and other effects on body composition."

A number of studies have shown that dietary CLA can reduce the development of breast cancer and slow its spread to other tissues. The beneficial effects seem to occur even at relatively low levels of CLA, she adds.

The BioCLA consortium has been running for more than three years and seeks to boost the levels of CLA in cows, sheep and goats. Teagasc has been looking at increasing CLA levels "through the animal dietary approach", Stanton says.

The research has involved a detailed study of how CLA is formed in the rumen of the cow before it becomes present in the milk. "Polyunsaturated fatty acids go into the rumen and are acted upon by bacteria there," she says. The process is known as the "biohydrogenation" of these fatty acids.

The useful CLA is found as an intermediate within the rumen but must first change temporarily into "trans-vaccenic acid" so it can be absorbed into the cow before reappearing as CLA once in the udder, she explains.

The driver of this reconversion is an enzyme known as delta nine desaturase. "That is the key enzyme when you look at CLA conversion." Between 70 to 90 per cent of CLA conversion is dependent on the presence of this enzyme in the mammary gland. She works in collaboration with University College Cork's alimentary pharmabiotic centre and with colleagues has conducted a range of studies looking at how CLA levels might be raised by adjusting the bovine diet.

The quickest way to have an impact is to put the animals out to grass. "Once the cows go out onto pasture CLA enrichment is doubled," she says. This gives Ireland an advantage, given cows are kept on grass for much longer here than elsewhere in Europe.

There have been extensive tests done on introduced polyunsaturated acids given as supplements, including sunflower and linseed oils and also rape and fish oils. The first two were shown to be the best at boosting CLA levels, she says.

The cow breed seems to matter less than the characteristics of a given animal, she adds.

Tests have also been carried out on how to get the CLA into productive use in the person consuming it. The research confirmed that CLA enriched cheeses could be made and the substance would remain stable during cheese ripening.

Cheeses produced by Stanton were used in human trials which looked at texture and taste, but also their ability to lower cholesterol and alter the fatty acid mix found in the blood. The tests were done in Rome and results were very positive for those ingesting the CLA cheese, Stanton says.

There is a greater challenge proving the anti-cancer aspects of CLA-enriched foods, but work is under way in collaboration with Dublin City University, she adds. The work has so far shown that CLA does have antiproliferation effects on colon and breast cancer cell lines.

Stanton is also looking at CLA levels in beef fat and at using microbes to produce CLA.