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Nutrition Department and Graduate Program in Nutrition, The Pennsylvania State University, University Park, PA 16802
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ABSTRACT |
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 TOP ABSTRACT INTRODUCTIONBiomarkersSafetyCONCLUSIONREFERENCES |
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KEY WORDS: • functional foods • health • biomarkers • oligofructose • inulin
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INTRODUCTION |
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TOPABSTRACTINTRODUCTIONBiomarkersSafetyCONCLUSIONREFERENCES |
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). Unfortunately, compelling scientific
evidence does not substantiate some of these beliefs. If consumer
confidence in the food supply is to remain high, it is essential that
consumers receive factual and reliable information to make informed
decisions about the merits or risks associated with changing dietary
habits.
The term "functional food" is surfacing as a generic descriptor
of the benefits that accompany ingesting foods that go beyond those
accounted for merely by the nutriture provided (Milner 1998
). The Institute of Medicine of the National Academy
of Sciences (1994)
has expanded this definition to include
"any food or food ingredient that may provide a health benefit
beyond the traditional nutrients it contains." Although not a legal
term, the concept of functional foods is gaining consumer acceptance.
Interest in the health benefits of foods has been sparked by factors
including rising health care cost (Hanks 1992
),
legislative changes that permit claims for foods and associated
components (Clydesdale 1997
, Kottke 1998
), and by the emergence of new and exciting scientific
discoveries (Farr 1997
, Milner 1998
). Increasingly, scientists are being asked to clarify the
specific role that foods or their components contribute to wellness and
disease prevention.
One of the most compelling reasons for the widespread interest in
functional foods comes from the rather consistent findings that
increased fruit and vegetable consumption is accompanied by a reduction
in the risk of heart disease and cancer (Craig 1997
,
de Lorgeril et al. 1998
, Potter and Steinmetz 1996
). A host of physiologically active components, both
essential nutrients and allelochemicals, may contribute to these
reported health benefits (Milner 1996
). Considerable
evidence reveals that allelochemicals, sometimes referred to as
"phytochemicals," likely contribute to this disease resistance,
as well as to improved performance (Diplock et al. 1998
). Although many have been proposed to function as
antioxidants, it is possible and quite probable that other mechanisms
of action are involved. Table 1 provides a listing of some of the varied types of dietary
microconstituents that may well influence the ability of an individual
to achieve his or her genetic potential and minimize the risk of
disease. Although literally hundreds of phytochemicals occur in plants,
this does not imply that animal products are without benefit. In fact,
evidence that such diverse compounds as (n-3) fatty acids from fish and
conjugated linoleic acid in milk and meat products can alter
physiological processes raises issues about what should be the ideal
balance and types of foods consumed (de Deckere et al. 1998
, West et al. 1998
).
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). Although heating tomatoes may improve
lycopene availability and thus improve its chances of altering
oxidative stress (Rao and Agarwal 1998
), recent studies
from our laboratory suggest that heating unpeeled garlic may reduce its
anticancer potential (Song and Milner, 1999
). Because a
variety of foods and their components are emerging as factors capable
of modifying growth, development, performance and disease resistance,
it will become increasingly important to clarify the effects that home
and commercial processing have on these benefits and thus consumer
decisions to shift or not modify dietary habits. Because more than one
constituent probably contributes to the benefits of most functional
foods, it is important to understand the dynamic interactions that
occur among the various components of the entire diet. Such discoveries
will probably influence perceptions about what is appropriate nutrition
and necessitate a new vocabulary, ranging in terms from apigenin to
zeaxanthin. Thus, in all likelihood, a new and expanded interpretation
of the A to Zs in nutrition will emerge. In the process, individuals
will gain a better understanding that adequate nutrition is more than
calories and essential nutrients. Although none of these components can
be considered magical bullets, they nonetheless may be important
modifiers and thus key factors in "optimizing" nutrition.
However, the merit of exaggerated ingestion of nonessential or
essential nutrients will likely be very dependent on the individual
consuming the food. Variation in genetics, physiologic state and the
composition of the entire diet will likely determine whether a response
to exaggerated intakes occurs. This concept of functional foods is not without controversy and even condemnation. Much of the concern arises from the view that although a diet may justifiably be characterized as "good or bad," the use of these terms to describe foods is inappropriate. In fact, concepts about functional foods could conceivably create a false sense of security about an individual's eating behavior. Furthermore, although total fruit and vegetable consumption is increasingly linked to a reduction in risk of several diseases, the association is far less impressive when a specific food or component is correlated. Regardless, there is little reason to believe that consumer acceptance of this concept will dwindle in the foreseeable future. Accepting this movement as an opportunity to "optimize nutrition" rather than to endorse good or bad foods or as a gimmick to foster sales will surely make it more palatable to most.
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Biomarkers |
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TOPABSTRACTINTRODUCTIONBiomarkersSafetyCONCLUSIONREFERENCES |
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). The use of multiple long-term intervention studies
to adequately assess the merits of increased intake of selected foods
or components would be impractical and cost prohibitive. Thus,
alternative procedures must be established. Identification of sensitive
and reliable biomarkers will be key to adequately assessing the true
effect of foods and components. It is likely that biomarkers similar to
those used for environmental exposures (Suk and Collman 1998
, Timbrell 1998
) will be required for
adequate evaluation of the merits and risk of exaggerated intakes of
functional foods and components. Thus biomarkers capable of assessing
the following will be required: 1) active agents capable of
modifying target tissues (Intake Biomarkers), 2) specific
biological responses that relate directly to either disease risk or
health maintenance (Effect Biomarkers), and (3) modifiers of the
response by genetic and other environmental factors (Susceptibility
Biomarkers). Figure 1
reveals the multiple and dynamic interrelationships that occur
among these three markers. Obviously, to assess whether a food or its
constituent is having a physiologic effect, it is imperative that valid
intakes and exposures to the active site(s) be determined. This
assessment is by itself not an easy task due to the questionable
reliability of food disappearance data and the dearth of
information available about many, if not most of the functional food
constituents of the diet (Ervin and Smiciklas-Wright 1998
, de Vries et al. 1998
). Effect biomarkers
refer to the consequences of interactions between a food component and
a specific genomic, biochemical, cellular or physiologic event.
Generally, the effect biomarkers are aimed at predicting a
long-term consequence such as general health or disease risk.
However, some may be more immediate, including those associated with
physical or mental performance. Some effect biomarkers may actually not
be within the body proper such as the effect seen with the biofidogenic
stimulation caused by enhanced intake of inulin and oligofructose
(Roberfroid 1993
). Clearly, the sensitivity of
the effect biomarker is highly dependent on a number of factors,
including genetics and environmental factors. Collectively, these
factors constitute susceptibility biomarkers that can affect the effect
biomarker being examined. It is assumed that all individuals will not
benefit equally from the enhanced intake of specific foods or their
components. To assess who might benefit most, it is imperative that a
series of susceptibility biomarkers that take into account genetics and
environmental factors be employed. Understanding these
interrelationships will be critical in providing consumers with
information about what should and should not be attempted when
considering modifications in dietary habits. Universal acceptance of
these bioindicators will surely be needed given our global economy.
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Safety |
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TOPABSTRACTINTRODUCTIONBiomarkersSafetyCONCLUSIONREFERENCES |
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).
Excessive intakes of nutrients are well documented to elicit adverse
effects. During the past few years, the Food and Nutrition Board of the
National Academy of Sciences has devoted considerable attention to the
upper safe limit for intake of essential nutrients. It would be wise to
develop a similar philosophy for functional foods and their
biologically active components. Although it is generally assumed that
toxicity is enhanced when compounds are removed from their complex
naturally occurring matrix, upper safe limits for their intake must
also be established. It is particularly important that any vulnerable
segments of society be considered when establishing an upper safe limit
and permissible intake for functional foods and their biologically
active components. For example, although data are rather compelling
that increased soy consumption may reduce the risk of heart disease and
cancer (Hsieh et al. 1998
, Tham et al. 1998
), there are other data that suggest possible harmful
effects. In vivo studies by Hsieh et al (1998)
suggest
that exaggerated soy intake may increase the risk of tumor
proliferation in some individuals. Effective criteria for validating appropriate end points and for establishing upper safe limits must be developed and used universally. Such information would allow for recommendations that reveal, for example, the intake of oligofructose or inulin that might be expected under most circumstances to reduce the risk of cancer and optimize changes in gastrointestinal flora, yet would minimize any chances of complications. Indeed, overindulgence of foods can be detrimental, if not lethal.
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CONCLUSION |
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TOPABSTRACTINTRODUCTIONBiomarkersSafetyCONCLUSIONREFERENCES |
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FOOTNOTES |
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REFERENCES |
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TOPABSTRACTINTRODUCTIONBiomarkersSafetyCONCLUSIONREFERENCES |
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2. Craig W. J. Phytochemicals: guardians of our health. J. Am. Diet. Assoc. 1997;97:S199-S204[Medline]
3. de Deckere E. A., Korver O., Verschuren P. M., Katan M. B. Health aspects of fish and n-3 polyunsaturated fatty acids from plant and marine origin. Eur. J. Clin. Nutr. 1998;52:749-753[Medline]
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5. de Vries J. H., Hollman P. C., Meyboom S., Buysman M. N., Zock P. L., van Staveren W, A. & Katan M. B. Plasma concentrations and urinary excretion of the antioxidant flavonols quercetin and kaempferol as biomarkers for dietary intake. Am. J. Clin. Nutr. 1998;68:60-65[Abstract]
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Song K, Milner J. Heating garlic inhibits its ability to suppress 7,12-dimethylbenz(a)anthracene-induced DNA adduct formation in rat mammary tissue. J. Nutr. 1999;129:657-661
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