Scientists believe the protein lectin could explain the chemical changes which cause some cancer cells to spread.

Professor David Rogers from Portsmouth University first discovered the unique qualities of the protein 20 years ago when he did a survey of lectins in British marine algae.

Matthew Hill reports on the discovery

He says seaweed containing lectins can be found on all UK coasts which are rocky. But it is not found on sandy shores.

The University of the West of England in Bristol is doing research on the protein.

Researchers collect the seaweed, liquidise it and separate the lectin from it.

The lectin is then attached to cancer cells and causes them to clump together.

Growing seaweed

Professor Ray Griffin of the University of the West of England said: "The lectins allow us to explore the molecules that hold the cells together in a way that is very difficult by other techniques.

Professor Ray Griffin: lectin may track cancer spread

"Different tumours of different levels of aggressiveness respond differently to the lectins."

The protein is quite hard to come by. Fourteen kilograms of seaweed is required to make just five miligrams of lectin.

Professor Rogers says if lectin is found to be effective in the fight against cancer it may be needed in large volumes.

That would mean it would have to be cultivated or the genes would have to be taken out of the seaweed.