The discovery that fruit and vegetables contain substances called phytochemicals which protect against cancer has, predictably, led to further human attempts to improve on nature (Ed.- because nature is not patentable). The Institute of Food Research (IRF) in Norwich is breeding ‘turbocharged’ broccoli with high phytochemical levels. Herbalforce Natural Products of Tetbury is selling Revital - phytochemicals in a capsule.

Dr. John Wilkinson of Middlesex University is cautious as to whether ‘human-improved’ versions will be effective. "We have discovered about 40,000 of these chemicals so far, but have little idea how they function. It may be that they confer benefit through the combined effect of a whole orchestra of chemicals (in the fruit and vegetables) and it has already been found with minerals and vitamins that more is not always better. Often a medium level is more benificial than a higher level and sometimes it is the relative proportion of a range of minerals and vitamins that counts."

The range of plants with identifiable beneficial effects is growing daily. Sprouts, for instance, contain sinigrin which breaks down into allyl isothiocyanate and persuades precancerous cells to commit suicide. So powerful is their effect that Dr. Wilkinson believes that even an occasional meal containing sprouts would keep the colon free of these cells. All cruciferous vegetables - broccoli, sprouts, cabbage, cauliflower, turnips, kale and kohlrabi - contain isothiocyanates and indoles, both of which have anti-cancer properties, but sprouts are the strongest.

Commercially grown broccoli has low levels (thus the IFR work above).

Forgotten by many now, and reduced to a garnish, watercress used to be a staple source of nutrition. Provided it is grown organically, watercress is a veritable powerhouse of goodness:

• Just 100 grams (3.5 oz.) supplies 100% of the recommended adult intake of vitamin C, and 52% of the recommended adult intake of vitamin A
• It delivers more iron than spinach and more calcium than milk by weight
• The mustard oil which gives its leaves their peppery taste is thought to be anti-carcinogenic

One US study showed that smokers eating 50 grams a day were able to excrete higher levels of tobacco carcinogens through their urine. Some scientists consider that it may also help slow the development of prostate tumours.