Network Health Dietitians July 08 Issue 36

polyphenols
by Dr Amy V Gasper and Dr Paul A Kroon
Phytochemicals and Health Programme,
Institute of Food Research
Apple polyphenols and vascular health
There is increasing evidence that Evidence for health effects of poly- either due to metabolism or colonic
diets rich in fruits and vegetables phenols
fermentation by gut bacteria. Stud-
are associated with a reduced risk
The potential health effects of ies using model systems to study
of chronic disease such as cardio-
consuming polyphenols have been biological mechanisms may not take
vascular disease CVD (1).
studied for many years using cell these bio-transformations into ac-
This may partly be due to the
culture model systems (cells derived count.
abundance of plant chemicals
from tissues of the human body and In addition, even a single item of
(phytochemicals) known as poly-
grown in petri dishes). These models food consists of a complex mixture
phenols that occur in these foods.
help us to understand the underlying of phytochemicals and nutrients
We are interested in a particular
biological mechanisms for a pro- which may interact, possibly syn-
class of polyphenols, occurring natu-
tection against CVD. Much of the ergistically, with each other. There-
rally in apples, in relation to protec-
interest in potential health beneﬁ ts of fore a major challenge is to design
tive effects against vascular disease.
individual polyphenolic compounds human intervention studies in which
has focused on their antioxidant health beneﬁ ts of normal dietary
Apple polyphenols
properties (5), but it is becoming intake can be assessed using whole
The main function of polyphenols
apparent that the protective ef- foods in order to discover the under-
for plants is to improve their ability to
fects may also be due to alternative lying mechanisms within the body.
mechanisms (6). For example, in our
withstand disease and to promote
Existing human intervention studies
laboratory we have recently shown
pollination by providing colour to
of ﬂ avonoids and ﬂ avonoid-rich
that quercetin metabolites at con-
attract insects (2). Apples contain
foods in relation to CVD risk tend to
centrations achievable in the diet, involve sources from tea, cocoa and
a class of polyphenol known as
when applied to a cell culture, inhib- soy. A recent review of these studies
ﬂ avonoids which are characterised
ited the expression of cell adhesion concluded that future studies should
by the presence of more than one
molecules involved in inﬂ ammation,
examine dose-response effects and
(poly) phenol group. Flavonoids are
a key event in the development of
be of sufﬁ cient duration to assess
further subdivided into categories
CVD (7).
clinically relevant endpoints (Hooper
such as anthocyanins, ﬂ avanols, and
Other effects seen in laboratory
et al, in press).
ﬂ avones found abundantly in certain
studies include improvements in the
foods (table 1).
cardiovascular system, including
An apple a day… the FLAVO Study
In Europe, 74 percent of total
decreasing oxidation of LDL cho-
The aim of the FLAVO study is
polyphenol intake can be attributed
lesterol (8), a harmful process that
to assess the effect of eating two
to fruit consumption, with apples
allows cholesterol to accumulate
varieties of apple puree (either high
providing 30 and 40 percent for
in blood vessels. Also inhibiting the
or low in polyphenolics) in compari-
women and men, respectively (3).
aggregation of blood platelets (9),
son to a low-dose aspirin on platelet
Intake varies greatly depending on
which contributes to the risk of blood
function and other risk factors of
the variety of apple consumed and
clots that produce stroke and heart
cardiovascular disease. We are in-
other factors such as climate, grow- attack and increasing blood ﬂ ow to
terested in both acute effects (over
ing and storage conditions. Cider the brain relating to cognitive func-
several hours) and more long term
apples such as the bittersweet Eng- tion (10). However it’s important to
effects (over a two week period).
lish varieties, Michelin and Dabinett, consider that eating apples results in
Serving the apple as a puree reduc-
are characterised by a higher level several bio-transformations of dietary
es the variation in the bioavailability
of phenolics compared with dessert phytochemicals within the gastro-
(the concentration of polyphenols
apples (4). intestinal tract prior to absorption,
reaching the circulation through
the blood) that may be caused by
differences in chewing between
Classiﬁ cation Examples Food sources
individuals.
In total, 26 healthy volunteers
Anthocyanins Delphinidin, cyanidin Strawberry, grape
were recruited into the study from
Flavanols Epicatechin, Catechin Apple, tea, cocoa
January 2007 to January 2008. Each
Flavonol Quercetin, Kaempferol Onion
volunteer consumed both variet-
ies of apple puree and a low dose
Flavanones Tangeretin, Hesperetin Citrus fruit, liquorice
aspirin tablet over a total period of
Flavones Luteolin, Apigenin Red pepper, celery 16 weeks. The effects of consuming
Isoﬂ avones Genistein, Daidzein Soybeans, chickpeas
one tin of apple puree or one aspirin
tablet per day for two weeks will be
Table 1 Dietary sources of polyphenols
compared in relation to markers of
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