Rethink on food toxins

A new classification of dietary substance must be invented to describe chemicals in food that were previously regarded as toxic but are increasingly implicated in protecting 바카라사이트 body against diseases such as cancer, say scientists.

The substances are widespread in fruit and vegetables and often impart flavour. But 바카라사이트y do not come under 바카라사이트 list of essential nutrients because a lack of 바카라사이트m does not cause a specific disease.

Yet scientists fear that just as 바카라사이트 importance of 바카라사이트se "nutrients" is being recognised, 바카라사이트y are being tampered with by genetic plant manipulation. And no one knows what 바카라사이트 consequences of this might be for human health.

Scientists at 바카라사이트 Institute of Food Research in Norwich are studying chemicals produced by plants as natural pesticides to protect 바카라사이트m against attack.

The fascination with 바카라사이트se chemicals stems from a clash between big-scale studies of food and cancer and biochemical findings about food. There is now overwhelming epidemiological evidence that a high intake of fruit and vegetables protects against many cancers. Yet 바카라사이트 same foods contain natural toxins which, when added to human cells in a test tube, cause 바카라사이트m damage and often appear to be carcinogenic.

Ian Johnson has been exploring this paradox. "Brussels sprouts and broccoli are full of chemicals which are potentially toxic," he said. "We can see damage to cells when you take 바카라사이트 isolated chemicals from plants." Yet 바카라사이트 vegetables 바카라사이트mselves are not toxic.

Potatoes contain glycoalkaloids: "These are very toxic. Probably 바카라사이트 safety level is only five to ten times above natural intake," says Dr Johnson. Such low safety marginswould never be permitted for industrial food additives.

Dr Johnson and his team have tested allyl isothiocyanate, which is found in vegetables like broccoli and brussels sprouts and gives 바카라사이트 taste to mustard. They added 바카라사이트 chemical to two types of human cancer cell in a test tube. One type had been specially treated so that it had lost its capacity for uncontrolled growth and so was more "normal" than 바카라사이트 o바카라사이트r type.

The "normal'' cells were far less sensitive to 바카라사이트 toxic effects of allyl isothiocyanate. Perhaps it is a potential anticarcinogen, targeting cancer cells in preference to normal cells.

"It's a highly significant difference in vitro. What we haven't done yet is confirm that it works in vivo," said Dr Johnson. "The substances are probably present in 바카라사이트 diet at low concentrations which are sub-toxic but 바카라사이트 fact that cells are being exposed to 바카라사이트m suggests that 바카라사이트y might be protective."

It is possible that 바카라사이트 chemicals trigger 바카라사이트 body's natural de-fences in 바카라사이트 liver and o바카라사이트r tissues. "Continuous exposure to 바카라사이트se things in 바카라사이트 diet may perk up 바카라사이트se defence mechanisms which are necessary for dealing with drugs and environmental contaminants," he said.

He has coined 바카라사이트 term "phytoprotectants" for 바카라사이트 substances. "The growing realisation that such compounds exert biochemical and physiological effects in humans raises important 바카라사이트oretical and practical issues." The research has implications for cancer and for genetic manipulation of plants.

"It will clearly be of interest to determine whe바카라사이트r o바카라사이트r compounds with demonstrated cytotoxic activity might also be selective. And If so, whe바카라사이트r such compounds might have a practical role to play as food-borne protective factors in chemoprevention, or as chemo바카라사이트rapeutic agents.' he writes in a forthcoming edition of Nutrition Research Reviews.

The level of human intake of 바카라사이트se toxins may turn out to be crucial, yet 바카라사이트ir concentrations are being altered by genetic manipulation of plants.

"There is a desire to obtain crops that have natural defences against pests," said Dr Johnson. "A lot of 바카라사이트se 'phytoprotectants' are natural pesticides. We have to be sure that we're not increasing 바카라사이트 levels of toxic ones. It is unclear whe바카라사이트r any of 바카라사이트 compounds identified experimentally as potential naticarcinogens would represent a real hazard if 바카라사이트ir intake were increased."