Overview of bioactive compounds in foods.

Introduction Food, besides supplying nutrients, contains a wide variety of bioactive substances, especially food of plant origin. The Swiss sage and physician Paracelsus (1493-1541) regarded plants as being a source of food, medicine and poison. He noted that ‘All things are poisons and nothing is without toxicity. Only the dose prevents anything not to be poisonous’. The term toxicity is generally regarded as the ability of a substance to cause injury when tested in isolation, whereas the term hazard is regarded as the ability of that substance to cause harm under the conditions in which it is used. Risk can be regarded as a measure of hazard. In recent years it has been recognized that bioactive compounds may confer benefits to health, rather than harm. An obvious example is that of ethanol where moderate intakes appear to decrease risk of cardiovascular disease and all-cause mortality in middle-aged and elderly men and women [l]. On the other hand, the same dose of alcohol in a young woman confers an increased risk of premature mortality from cancer [Z]. Moreover, even moderate alcohol consumption will have adverse effects on those with liver disease. Thus the risk to an individual from bioactive materials in food and drink depends not only upon the potency of the substance, dose, duration and timing (exposure) but on the age, gender and health of the individual. The term phytochemical is often used to refer to xenobiotics from plants. It follows that the more varied the diet, the greater the chances of being exposed to phytochemicals. Most phytochemicals induce enzymes that lead to their breakdown and