Phytochemicals are naturally occurring, biologically active chemical compounds in plants. They are grouped based on their functions and sometimes sources. Examples of the widely studied groups are flavanoids, phyto-oestrogens, phytosterols and carotenoid.

The functions of phytochemicals are varied and include protecting blood vessels, enhancing the effects of vitamin C, and facilitating cholesterol excretion from the body.

Some good sources of phytochemicals include broccoli, cauliflower, cabbage, lettuce, citrus fruits, mangoes, whole wheat, corn, and ginger.

The quantity of phytochemicals present and consumed as food is not known to be harmful among the foods widely eaten. Harmful forms are generally found in plants already identified as not being safe for human consumption and are not usually eaten.