Cancer linked to clean living and great vegetables

The modern obsession with cleanliness, already blamed for the dramatic rise in asthma cases, may also have left people more vulnerable to cancer, according to medical researchers.

Clean homes and an insistence of perfect-looking vegetables are falling under suspicion for having prevented exposure to mild infections and natural anti-cancer agents now thought to play a key role in protecting against the disease.

Researchers are now raising the possibility of deliberately exposing new-born children to a cocktail of microbes to give their immune systems the cancer-fighting abilities once acquired from grubby housing conditions.

Evidence that too much hygiene is bad for health has been mounting in recent years, following claims that the dramatic rise in asthma and allergies world-wide is due to lack of exposure to microbes that "train" the immune system not to over-react to dust and pollen.

According to Prof Mel Greaves, of the Institute of Cancer Research, in London, evidence is now emerging that the 10-fold increase in childhood leukaemia over the last 80 years is tied to socio-economic class, pointing to a link with hygiene standards.

"What has happened over the last century is that we have got a lot cleaner, and much less crowded and infants aren't challenged with infections over the first year of life," Prof Greaves said. "But when they go to school, they do get exposed to infections, and this might then precipitate a very strong immune response."

Prof Greaves said that the result would be a massive release of disease-fighting chemicals by the body, which can damage bone-marrow cells, triggering leukaemia.

According to Prof Greaves, the hygiene effect would explain the recently revealed link between ear infections and reduced risk of leukaemia. He added that there may even be a case for giving babies vaccines of microbes to which they are no longer exposed, to protect against later cancer.

The fad for perfect-looking vegetables may also be increasing the risk of developing cancer. Studies of broad-leaf vegetables like lettuce have shown that when attacked by plant viruses, they fight back using compounds called salicylates. Related to aspirin, these compounds are thought to be natural anti-cancer agents.

Vegetables grown under strictly controlled conditions - as they are for supermarkets - are however protected from the infections that trigger the release of these compounds. Shoppers who insist on perfect-looking vegetables may thus be robbing themselves of natural anti-cancer agents, according to Prof Robin Phillips, a leading cancer expert at St Mark's Hospital, Middlesex.

He said: "Cabbages with black spots are actually packed with them - they're good for us. Our insistence on perfection may have backfired on us."

The Daily Telegraph, London