Phytochemicals (plant secondary metabolites) have received considerable interest in the last three decades in relation to their biosynthetic regulation in plants and also their health effects in animals and humans. There is increasing evidence from epi-demiological data, from in vitro cell studies, and from animal and human intervention studies that certain phytochemicals can significantly affect nutrition and health. Some of these effects are positive (e.g. reduc-tions in the risk of developing cancers, coronary heart disease and immune dysfunctions) whereas others can be negative (e.g. toxic non-protein amino acids and pro-carcinogenic furanocoumarins). Levels of phytochemicals and other plant defence compounds are modulated by many genotype-independent factors such as light, water, CO2, oxygen and ozone, nutrient supply, pesticides, levels of diseases and herbivore damage. Therefore different production methods for crops (conventional, low input and organic) have the potential to significantly affect the levels of the phy-tochemicals in the crops, and subsequently affect health and nutrition in the consumer
