Phytochemical



Phytochemicals are chemical compounds that occur naturally in plants (phyto means "plant" in Greek). Some are responsible for color and other organoleptic properties, such as the deep purple of blueberries and the smell of garlic. The term is generally used to refer to those chemicals that may have biological significance, for example carotenoids or flavonoids, but are not established as essential nutrients. There may be as many as 4,000 different phytochemicals having potential to affect diseases such as cancer, stroke or metabolic syndrome.

Phytochemicals as candidate nutrients
Without specific knowledge of their cellular actions or mechanisms, phytochemicals have been considered as possible drugs for millennia. For example, Hippocrates may have prescribed willow tree leaves to abate fever. 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 staple, over-the-counter drug aspirin.

Specific phytochemicals, such as fermentable dietary fibers, are allowed limited health claims by the US Food and Drug Administration (FDA).

Some phytochemicals with physiological properties may be elements rather than complex organic molecules. For example, selenium, which is abundant in many fruits and vegetables, is a dietary mineral involved with major metabolic pathways, including thyroid hormone metabolism and immune function. Particularly, it is an essential nutrient and cofactor for the enzymatic synthesis of glutathione, an endogenous antioxidant.

Clinical trials and health claim status
Lycopene from tomatoes has been tested in human studies for cardiovascular diseases and prostate cancer. These studies, however, did not attain sufficient scientific agreement to conclude an effect on any disease. The FDA position reads:

""Very limited and preliminary scientific research suggests that eating one-half to one cup of tomatoes and/or tomato sauce a week may reduce the risk of prostate cancer. The United States Food and Drug Administration concludes that there is little scientific evidence supporting this claim.""

Phytochemical-based dietary supplements can also be purchased. According to the American Cancer Society, "Available scientific evidence does not support claims that taking phytochemical supplements is as good for long-term health as consuming the fruits, vegetables, beans, and grains from which they are taken."

Food processing and phytochemicals
Phytochemicals in freshly harvested plant foods may be degraded by processing techniques, including cooking. For this reason, industrially processed foods likely contain fewer phytochemicals than fresh or frozen foods, and therefore would not contribute to dietary intake that may lower risk of preventable diseases. The main cause of phytochemical loss from cooking is thermal decomposition.

A converse exists in the case of carotenoids, such as lycopene present in tomatoes, which may remain stable or increase in content from cooking due to liberation from cellular membranes in the cooked food. Food processing techniques like mechanical processing can also free carotenoids and other phytochemicals from the food matrix, thus increasing dietary intake.