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Phytochemical

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PhytochemicalsFOUND IN DARK CHOCLATE-- are chemical compounds, such as beta-carotene, that occur naturally in plants. The term is generally used to refer to those chemicals that may affect health, but are not yet established as essential nutrients.[1] While there is abundant scientific and government support for recommending diets rich in fruits and vegetables,[2] there is only limited evidence that health benefits are due to specific phytochemicals.[1]

Phytochemicals as candidate therapeutics

Phytochemicals have been used as 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 became the staple over-the-counter drug called aspirin. There is evidence from laboratory studies that phytochemicals in fruits and vegetables may reduce the risk of cancer, possibly due to dietary fibers, polyphenol antioxidants and anti-inflammatory effects. Specific phytochemicals, such as fermentable dietary fibers, are allowed limited health claims by the US Food and Drug Administration (FDA).[3]

An important cancer drug, Taxol (paclitaxel), is a phytochemical initially extracted and purified from the Pacific yew tree.

Among phytochemicals from edible plants with promise for deterring disease, diindolylmethane, from brassica vegetables (broccoli, cauliflower, cabbage, kale, Brussels sprouts) is being tested against recurring respiratory papillomatosis tumors (caused by the human papilloma virus), is in Phase III clinical trials for cervical dysplasia (a precancerous condition caused by the human papilloma virus) and is in several clinical trials for prostate cancer.[4]

Some phytochemicals with physiological properties may be elements rather than complex organic molecules. Abundant in many fruits and vegetables, selenium, for example, is involved with major metabolic pathways, including thyroid hormone metabolism and immune function.[5] Particularly, it is an essential nutrient and cofactor for the enzymatic synthesis of glutathione, an endogenous antioxidant.[6]

Clinical trials and health claim status

There are currently many phytochemicals possibly having medicinal properties in clinical trials for a variety of diseases. Lycopene, for example, from tomatoes has been tested in clinical trials for cardiovascular diseases and prostate cancer. These studies, however, did not attain sufficient scientific agreement to conclude an effect on any disease.[7] 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."

Likewise, although lutein and zeaxanthin may affect visual performance and inhibit macular degeneration and cataracts, there was insufficient scientific evidence from clinical trials for such a specific effect or health claim.[8][9]

Food processing and phytochemicals

Phytochemicals in freshly harvested plant foods may be destroyed or removed by modern processing techniques, possibly including cooking.[10] For this reason, industrially processed foods likely contain fewer phytochemicals and may thus be less beneficial than unprocessed foods. Absence or deficiency of phytochemicals in processed foods may contribute to increased risk of preventable diseases.[11][12]

Interestingly, a converse example may exist in which lycopene, a phytochemical present in tomatoes, is either unchanged in content[13] or made more concentrated[14] by processing to juice or paste, maintaining good levels for bioavailability.

See also

Footnotes

  1. ^ a b Micronutrient Information Center, Linus Pauling Institute, Oregon State University
  2. ^ "Fruits and Veggies, More Matters". Centers for Disease Control and Prevention, US Department of Health and Human Services. 2010. Retrieved 18 January 2010.
  3. ^ US FDA, Health Claims that Meet Significant Scientific Agreement
  4. ^ "Diindolylmethane Clinical Trials". ClinicalTrials.gov, US National Institutes of Health, Department of Health and Human Services. 2010. Retrieved 18 January 2010.
  5. ^ Brown, KM; Arthur, JR (2001). "Selenium, selenoproteins and human health: a review". Public health nutrition. 4 (2B): 593–9. doi:10.1079/PHN2001143. PMID 11683552.
  6. ^ Papp, LV; Lu, J; Holmgren, A; Khanna, KK (2007). "From selenium to selenoproteins: synthesis, identity, and their role in human health". Antioxidants & redox signaling. 9 (7): 775–806. doi:10.1089/ars.2007.1528. PMID 17508906.
  7. ^ Qualified Health Claims Subject to Enforcement Discretion, Docket No. 2004Q-0201, US Food and Drug Administration
  8. ^ US FDA, Qualified Health Claims: Letter of Denial - Xangold Lutein Esters, Lutein, or Zeaxanthin and Reduced Risk of Age-related Macular Degeneration or Cataract Formation (Docket No. 2004Q-0180)[1]
  9. ^ Krishnadev N, Meleth AD, Chew EY (2010). "Nutritional supplements for age-related macular degeneration". Current Opinion in Ophthalmology. 21 (3): 184–9. doi:10.1097/ICU.0b013e32833866ee. PMC 2909501. PMID 20216418. {{cite journal}}: Unknown parameter |month= ignored (help)CS1 maint: multiple names: authors list (link)
  10. ^ Cooking and nutrient loss, World's Healthiest Foods
  11. ^ Liu, RH (2004). "Potential synergy of phytochemicals in cancer prevention: mechanism of action". The Journal of nutrition. 134 (12 Suppl): 3479S–3485S. PMID 15570057.
  12. ^ Rao, AV; Rao, LG (2007). "Carotenoids and human health". Pharmacological research. 55 (3): 207–16. doi:10.1016/j.phrs.2007.01.012. PMID 17349800.
  13. ^ Agarwal, A; Shen, H; Agarwal, S; Rao, AV (2001). "Lycopene Content of Tomato Products: Its Stability, Bioavailability and in Vivo Antioxidant Properties". Journal of medicinal food. 4 (1): 9–15. doi:10.1089/10966200152053668. PMID 12639283.
  14. ^ Dewanto, V; Wu, X; Adom, KK; Liu, RH (2002). "Thermal processing enhances the nutritional value of tomatoes by increasing total antioxidant activity". Journal of agricultural and food chemistry. 50 (10): 3010–4. doi:10.1021/jf0115589. PMID 11982434.
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