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Functional Foods for Health Program, Department of Food Science and Human Nutrition, University of Illinois, Urbana, IL and * Jean Mayer USDA Human Nutrition Research Center on Aging, Tufts University, Boston, MA
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INTRODUCTION |
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 TOP INTRODUCTION REFERENCES |
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). A significant direction
of the effort to understand the health benefits of plant foods and
the basis for the creation of functional foods, also called
nutraceuticals and designer foods, is the characterization of
their physiologically active constituents, phytochemicals. It has
long been appreciated that food plants contain significant
levels of low molecular weight, secondary metabolites with
important roles for plant protection (Rhodes 1996
). It seems likely
that much of the anticipated success in developing foods for which
scientifically valid health claims can be proffered will actually
derive from basic science studies with a goal of generating information
about these components.
After their isolation and chemical characterization,
phytochemicals have to be tested in animal models and human studies
that evaluate not only their safety and efficacy but also their
absorption, distribution, metabolism, excretion and mechanisms of
action. As our knowledge of these compounds grows, we will learn how
best to create new products through altering their concentrations,
combinations and/or their bioavailability. Progress is already being
made through careful reviews of selected phytochemicals against a
standardized set of scientific criteria, including chemistry, food
sources, intake, bioavailability, physiologic actions, functionality
and toxicity (International Life Sciences Institute 1998
). The food
components initially being reviewed by the International Life Sciences
Institute include epigallocatechin and epigallocatechin gallate,
genistein and daidzein, isothiocyanate, limonene, lycopene,
fructooligosaccharides, phytosterols, quercetin, and diallyl disulfide.
However, the list of candidate phytochemicals with a potential effect
on health is long and much work has to be done.
The majority of phytochemical research to date has targeted their
potential role in cancer chemoprevention (American Institute for Cancer Research 1996
, Murakami et al. 1996
). Although the number of human
studies in this area remains very limited, the promise is great as
indicated by laboratory and epidemiologic studies. The diversity of
putative anticancer mechanisms is almost matched by the diversity of
phytochemicals and includes inhibition of carcinogen activation,
induction of hepatic detoxification pathways, antioxidant action
against reactive oxygen species, enhancement of immune responses and
alteration of hormone metabolism (Table 1
)(Dragsted et al 1993
). Steinmetz and Potter (1991)
issued the warning
that "... There is a diet to which humans are adapted; this diet
includes regular exposure to substances on which human metabolism is
dependent, only some of which, to date, have been labeled as
`essential nutrients' ... vegetables and fruit contain the
anticarcinogenic cocktail to which we are adapted. We abandon it
at our peril." New evidence is emerging that also supports a
role for phytochemicals in the prevention of cardiovascular disease
(Howard and Kritchevsky 1997
). Special emphasis has been given to the
plant sterols, sulfur compounds and flavonoids in this regard.
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ACKNOWLEDGMENTS |
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FOOTNOTES |
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1 Presented at the symposium Phytochemicals:
Biochemistry and Physiology as part of Experimental Biology 96, April
14–18, 1996, Washington, DC. The symposium was sponsored by the
American Society for Nutritional Sciences. Published as a supplement to
The Journal of Nutrition. Guest editors for the symposium
publication were Clare Hasler, University of Illinois, Urbana, IL and
Jeffrey Blumberg, Tufts University, Boston, MA.
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REFERENCES |
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TOPINTRODUCTIONREFERENCES |
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1. American Dietetic Association Position of the American Dietetic Association: phytochemicals and functional foods. J. Am. Diet. Assoc. 1995;95:493-496[Medline]
2. American Institute for Cancer Research Dietary phytochemicals in cancer prevention and treatment. Adv. Exp. Med. Biol. 1996;401:1-340[Medline]
3. Dragsted L. O., Strube J., Larsen J. C. Cancer protective factors in fruits and vegetables: biochemical and biological background. Pharmacol. Toxicol. 1993;72:S116-S135
4.
Howard B. V., Kritchevsky D. Phtyochemicals and cardiovascular disease: A statement for healthcare professionals from the American Heart Association. Circulation 1997;95:2591-2593
5. International Life Sciences Institute (1999) Technical Committee on Food Components for Health Promotion. Crit. Rev. Food Sci. Nutr. (Submitted for publication).
6. Murakami A., Ohigashi H., Koshimizu J. Anti-tumor promotion with food phytochemicals: a strategy for cancer chemoprevention. Biosci. Biotech. Biochem. 1996;60:1-8
7. Rhodes M.J.C. Physiologically active compounds in plant foods: an overview. Proc. Nutr. Soc. 1996;55:371-384[Medline]
8. Steinmetz K. A., Potter J. D. Vegetables, fruit, and cancer: II. Mechanisms. Cancer Causes Control 1991;2:427-443[Medline]
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