Phytochemicals are chemical compounds that occur naturally in plants.
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.
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."
Phytochemicals and their health effects Intake of phytochemicals, such as, has been
associated with the maintenance of good health as well as possible reduction in disease risk
in cancer, cardiovascular diseases, diabetes, hypertension, stroke, metabolic syndrome and
other degenerative diseases.
However, to date, no non-nutrient phytochemical has been conclusively linked to lowering disease
risk.
Certain phytochemicals are responsible for the colour and other organoleptic properties
of the foods, such as the deep purple colour of blueberries and the peculiar odour of garlic.
There may be as many as 4,000 different phytochemicals in plant foods.
Among several major groups of phytochemicals, polyphenols include a large subgroup of compounds
known as flavonoids present in a wide range of fruits, vegetables and grains; isoflavones
mimic the action of female hormone - estrogen.
These seemingly estrogen-like substances from plant sources called phytoestrogens are under
study in preliminary research.
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.
See also
References
Further reading Higdon, J. An Evidence – Based Approach
to Dietary Phytochemicals. 2007.
Thieme.
ISBN 978-1-58890-408-9 Rosa, L.A. de la / Alvarez-Parrilla, E. / González-Aguilar,
G.A.
Fruit and Vegetable Phytochemicals: Chemistry, Nutritional Value
and Stability. 2010.
Wiley-Blackwell.
ISBN 978-0-8138-0320-3 Bongoni R, Steenbekkers LPA, Verkerk R, van
Boekel MAJS, Dekker M. Studying consumer behaviour related to the quality of food: A case on
vegetable preparation affecting sensory and health attributes.
Trends in Food Science & Technology.
2013;33(2):139-45.
Rao AV, Rao LG.
Carotenoids and human health.
Pharmacological Research.
2007;55(3):207-16.
Liu RH.
Potential Synergy of Phytochemicals in Cancer Prevention: Mechanism of Action.
J Nutr. 2004;134(12):3479S-85.
External links Phytochemical Database - United States Department
of Agriculture Phytochemicals at LPI - Linus Pauling Institute
at Oregon State University Article on Health Benefits of Antioxidants
and Phytochemicals - Dr Santosh Jain Passi - Nutritionist; Former Director, Institute
of Home Economics & Ms Akanksha Jain - Research Associate.