Gregg Carter wrote
> >...as well as a
> >new class of nutrients that have been identified for opitmal health and
> >resistance to disease called "phytochemicals."

> Staffan Lindeberg [replied]
 > "Hypothesized" is closer to the truth. They may be just markers for a
> healthy lifestyle.

Staffan-- the scientific thinking has gone far beyond armchair
hypothesizing regarding phytochemicals.  The list of these chemicals
(which now number in the thousands) and the beginnings of our
understanding of the underlying mechanisms connecting them to good health
is growing daily.  The American Society for Nutritional Sciences -- based
on their evaluation of information presented in peer-reviewed scientific
reports -- has published the following position statement regarding
one large class of phytochemicals:

"Specific low molecular weight phytochemicals with chemopreventive
activity are contained within a variety of plants. Cruciferous plants,
such as cabbage and broccoli, are excellent sources of indoles,
dithiolthiones, isothiocyanates and chlorophyllins. Legumes (soybeans,
peanuts, beans and peas) contain flavanoids, isoflavanoids and other
polyphenols that act as antioxidants and estrogenic agonists/antagonists.
Citrus fruits and licorice root contain mono- and triterpenes that act as
antioxidants, cholesterol synthesis inhibitors, and stifle growth of
rapidly dividing cells. Thioallyl derivatives are found in garlic, leeks
and onion, and prevent thrombi formation, decrease cholesterol synthesis,
and prevent DNA damage."

[For those unfamiliar with this organization, the ASNS is one of the most
important professional associations concerned with nutrition in the
acadmic world; it publishes the scientific journal The Journal of
Nutrition, whose current editor is in the Department of Biochemistry at
the  University of Wisconsin-Madison.]

Not to bore the list with a lot of scientific writing, but to show how we
are currently uncovering the physiological mechanisms linking particular
phytochemicals with particular health benefits (and thus to counter
Staffan's argument that current nutritional science regards the effects
of phytochemicals as merely hypothetical), I provide the following
excerpt from The Journal of Nutriton, v. 126, pp. 2098-2106 (Sept. 1996;
authored by Keith R. Martin, Mark L. Failla and J. Cecil Smith, Jr.):

"Numerous epidemiological studies support a strong inverse relationship
between consumption of carotenoid-rich fruits and vegetables and the
incidence of some degenerative diseases. One proposed mechanism of protection by
carotenoids centers on their putative antioxidant activity, although direct
evidence in support of this contention is limited at the cellular level. The antioxidant
potential of B-carotene(BC) and lutein (LUT), carotenoids with or without
provitamin A activity, respectively, was evaluated using the human liver cell line HepG2.
Pilot studies showed that a 90-min exposure of confluent cultures to 500
mol/L tert-butylhydroperoxide (TBHP) at 37C significantly (P < 0.05)
increased lipid peroxidation and cellular leakage of lactate dehydrogenase
(LDH), and decreased the uptake of 3H-alpha-aminoisobutyric acid and
3H-2-deoxyglucose. Protein synthesis, mitochondrial activity and glucose
oxidation were not affected by TBHP treatment, suggesting that the plasma
membrane was the primary site of TBHP-induced damage. Overnight incubation
of cultures with > 1 mol/L  dl-alpha-tocopherol protected cells against
oxidant-induced changes. In parallel  studies, overnight incubation of
HepG2 in medium containing micelles with either BC  or LUT (final
concentrations of 1.1 and 10.9 mol/L, respectively), the cell content
of the carotenoids increased from <0.04 to 0.32 and 3.39 nmol/mg
protein, respectively. Carotenoid-loaded cells were partially or completely
protected against oxidant-induced changes in lipid peroxidation, LDH
release and amino acid and deoxyglucose transport. These data demonstrate
that BC and LUT or their metabolites protect HepG2 cells against
oxidant-induced damage and that the  protective effect is independent of
provitamin A activity."

Cheers!

Gregg C.
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