IT is the superfood that Brits just cannot get enough of.

People in the UK munch their way through £60m worth of watercress a year – and 90 per cent is grown in Hampshire.

Today Southampton scientists have revealed that the vitamin-rich vegetable has the potential to fight breast cancer.

A trial found that eating just one portion was enough to halt the growth of breast cancer cells.

Now experts say it paves the way for using watercress to help reduce the risk of other types of the killer disease.

Its cancer fighting abilities come from a plant compound which is able to starve tumours of essential blood and oxygen by “turning off” a cancer signal in the body.

The encouraging results from a pilot project, led by Professor Graham Packham at the University of Southampton, is the first step to proving watercress can beat cancer.

He told the Daily Echo: “I was surprised that eating one portion of watercress was able to produce significant levels of this compound in the blood.

“We carried out this study with a handful of breast cancer survivors but it has the potential to have the same effect with other cancers too.”

The research was carried out in two phases, in the laboratory and in a dietary trial involving a small group of breast cancer survivors from Hampshire.

Laboratory tests showed that the compound phenylethyl isothiocyanate (PEITC), of which watercress is the richest natural source, had the ability to interfere with a critical function in cancer development.

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As tumours develop they rapidly outgrow their existing blood supply and further development is not possible until they are able to get enough oxygen and nutrients to maintain the growth of cancer cells.

So the cancer cells send out signals which cause the surrounding normal tissues to grow new blood vessels into the tumour, which then supply the essential nutrients, known as angiogenesis.

But what the study found in the lab was that PEITC was able to block the growth of new blood vessels and effectively starve the tumour.

Professor Packham then worked with Barbara Parry, senior research dietician at the Winchester and Andover Breast Unit, to see what effect eating an 80g portion of watercress had on 12 surviving breast cancer patients.

They spent nine hours at hospital where an initial blood sample was taken. They then each ate 80g of raw watercress. Throughout the day blood samples were taken at regular intervals to measure the levels of PEITC in the blood.

The research team was able to detect significant levels of PEITC in the blood that could potentially “turn off” the cancer signal.

Professor Packham added: “The research takes an important step towards understanding the potential health benefits of this crop since it shows that eating watercress may interfere with a pathway that has already been tightly linked to cancer development.

“This is not about a cure for cancer, it is more a preventative measure as part of a healthy lifestyle which reduces the risk of cancer.

“This was a small pilot study so there are no definitive answers here, but the signs are encouraging and this is the first step to proving the anti-cancer benefits of watercress. Now a larger study needs to be undertaken.”

The beneficial properties of watercress have been revered down the centuries. But until now no clinical investigations have been undertaken to demonstrate how eating watercress as part of a healthy diet exerted its protective influence on humans.

What this study shows is that watercress has the ability to suppress and prevent breast cancer cell development but it cannot cure cancer in a patient already diagnosed as the pathway has already been opened.

The £100,000 study was funded by The Watercress Alliance, made up of Hampshire and Dorset companies, Vitacress Salads, Alresford Salads and The Watercress Company.

Dr Steve Rothwell, from the Watercress Alliance, said: “We are very excited by the outcome of Professor Packham’s work which builds on the body of research which supports the idea that watercress may have an important role to play in limiting cancer development.

“It is fitting that the latest project is being carried out in Hampshire which is at the centre of UK watercress production.”