A tomato which contains three times more of a cancer-fighting substance than ordinary tomatoes has been developed by scientists. The tomatoes have been genetically modified to contain increased levels of lycopene.

A team of researchers stumbled on the find while developing late-ripening tomatoes. Purdue University in Indiana and the US Department of Agriculture are responsible for the breakthrough. Lycopene is an antioxidant which has been linked with cancer-fighting properties.

There is evidence of a huge ancient lake covering more than a million square kilometres on Mars. Early in the planet's history, about 3.5 billion years ago, the 1,100 metre deep lake would have contained almost 500,000 cubic kilometres of water. At some stage, the lake over-flowed and cut through a weak spot in its perimeter, the scientists believe.

Water surging through the gap formed the Ma'adim Vallis valley, which is between eight and 15 kilometres wide and one of the largest valleys in the Martian highlands. Originally, it has been thought that the valley was created by a ground water source.

China has grown a crop of multi-coloured wheat. Agricultural researchers have developed edible species which are black, purple, green, blue and coffee coloured. Cross breeding and genetic modification techniques were used to develop the breeds.

The work was carried out in Nanyang City in Central China, according to the Xinhua news agency. The varieties are said to be rich in elements like iodine, calcium, iron and zinc which help give them their colour. Wheat specialist Zhou Zhongpu has been working on the project for about 12 years and believes demand for the crop will be high from food producers.

Scientists have developed a new genetically engineered yoghurt bacteria that can clean teeth. Rats treated with the bacteria developed fewer cavities. The bacteria carries an antibody which fights the bugs causing tooth decay.

Genetically modified Lactobacillus zeae was developed by Lennart Hammarstrom of the Karolinska Institute in Stockholm. It fights Streptococcus mutans, which causes most dental decay. The two species clump together and slide harmlessly down the throat.

Nature reports that Hammarstrom's team is now developing lactobacilli which combat diarrhoea and stomach ulcers. He claims the technology could be available in one to two years but red tape and trials may mean it isn't available to the public for another decade.

According to scientists, young people with eating disorders should be made to rest in hot rooms. Research carried out in Sweden found temperatures of around 40 degrees Celsius can help treat anorexia and bulimia.

A seven-year study found 75 per cent of 168 patients treated with heat after meals had regained normal weight. The average recovery time was 14 months and only seven per cent had a relapse.

Patients are trained by computer to eat bigger portions of food. The warm room stops them from moving and burning off the energy. Patients are then taken to rest in a warm room where they can only move in a wheelchair so that they conserve energy.

Sex education videos have been made compulsory for adult giant pandas in China to stop the endangered species becoming extinct.

The China Giant Panda Breeding and Research Centre in Sichuan says the videos featuring both wild and captive pandas having sex will encourage them to mate. Researchers are now making all male pandas who reach sexual maturity watch the videos following successful experiments with so-called panda porn.

Anoraks are a possible health hazard, says a medical expert. A study carried out at Birmingham City Hospital found the hooded coats reduce the field of vision by up to half. The professor behind the research says this can be potentially dangerous when crossing a road.

Philip Murray, an ophthalmologist, has published his research in the Journal of the Royal Society of Medicine. He said : "Our researchers measured the binocular visual field of volunteers wearing four different styles of anorak. Most wearers pull the hood over their heads and we found that with the hood up, the field of vision is more than halved."