Phytochemical

As a term, phytochemicals is generally used to describe plant compounds that are under research with unestablished effects on health, and are not essential nutrients.

[4][5] Phytochemicals under research can be classified into major categories, such as carotenoids[6] and polyphenols, which include phenolic acids, flavonoids, stilbenes or lignans.

For example, salicin, having anti-inflammatory and pain-relieving properties, was originally extracted from the bark of the white willow tree and later synthetically produced to become the common, over-the-counter drug aspirin.

[16] The English yew tree was long known to be extremely and immediately toxic to animals that grazed on its leaves or children who ate its berries; however, in 1971, paclitaxel was isolated from it, subsequently becoming an important cancer drug.

[4][17] The phytochemical category includes compounds recognized as essential nutrients, which are naturally contained in plants and are required for normal physiological functions, so must be obtained from the diet in humans.

[23] Non-digestible dietary fibers from plant foods, often considered as a phytochemical,[24] are now generally regarded as a nutrient group having approved health claims for reducing the risk of some types of cancer[25] and coronary heart disease.

[4] For example, systematic reviews and/or meta-analyses indicate weak or no evidence for phytochemicals from plant food consumption having an effect on breast, lung, or bladder cancers.

[30][31] Further, in the United States, regulations exist to limit the language on product labels for how plant food consumption may affect cancers, excluding mention of any phytochemical except for those with established health benefits against cancer, such as dietary fiber, vitamin A, and vitamin C.[32] Phytochemicals, such as polyphenols, have been specifically discouraged from food labeling in Europe and the United States because there is no evidence for a cause-and-effect relationship between dietary polyphenols and inhibition or prevention of any disease.