Issue:
117
Page: 35
Scientific Journals Increasingly Skeptical of Antioxidant Research
by Stefan Gafner, PhD
HerbalGram.
2018; American Botanical Council
In its December 2017 issue, The Journal of Food
Composition and Analysis (JFCA) published an editorial in which it
announced that the journal “will no longer accept papers for review that employ
antioxidant and total phenolic assays.”1
The JFCA’s new policy follows a trend started by other
scientific journals that focus on natural products research and that no longer
accept or restrict acceptance of papers dealing with antioxidant activity of
extracts or isolates from plant, fungal, or animal sources. The Journal of
Ethnopharmacology lists “in vitro antioxidant activity” as a rejection
criterion, stating that such activity is “present in all plants” and thus is
less meaningful without additional data.2 Planta Medica and Fitoterapia
also reject manuscripts that report predictable biological activities, such
as the antioxidant activities of phenolic compounds.3,4
In his editorial, JFCA Editor-in-Chief James Harnly, PhD,
a research leader at the United States Department of Agriculture’s Food
Composition and Methods Development Laboratory, notes that there is little
evidence that antioxidant activities observed in vitro will have an impact on
health in animal or human studies.1 In addition, the tests used to
measure total antioxidant activity, such as the ORAC, DPPH, TEAC, and FRAP†
assays, are non-specific and prone to interferences, and therefore do not
provide reliable results. As a consequence, the JFCA will immediately
reject papers in which the data primarily rely on these assays. For manuscripts
that use these assays to provide additional data (e.g., to explain a mechanism
of action), the JFCA will request that the authors resubmit the paper after
omission of the antioxidant data.1
Interest in antioxidant activities started to grow in the
late 1990s because of data that established the involvement of reactive oxygen
species (ROSs) in a number of major health issues (e.g., inflammation,
cardiovascular disease, and cancer). The theory was that since antioxidants
were able to react with these ROSs in vitro, they might lead to the development
of agents capable of preventing some of the related health issues in humans.
According to PubMed — the extensive medical database maintained by the US National
Library of Medicine (a part of the US National Institutes of Health) — the
number of papers containing the term “antioxidant activity” in the title or
abstract has skyrocketed over the past two decades (Figure 1).
The usefulness of the data published on antioxidant
activities is rightfully a matter of debate in the scientific community.
Phenolic compounds, which play an important role in plant defense mechanisms,
occur widely in the plant kingdom.5,6 Plant defense mechanisms are
activated in response to plant pathogens, injury, or environmental factors.5-7
The increase in the concentration of ROSs is one of the initial defense
reactions observed in plants. In order to avoid damage caused by the increased
concentrations of ROSs, plant tissues use an array of antioxidant mechanisms,
including enzymes and antioxidant secondary metabolites.5,6 While
these antioxidant compounds play an important physiological role in plants,
much of their impact on human health has yet to be demonstrated.
Many dietary supplement and conventional food
manufacturers have products with antioxidant claims in their portfolio (e.g.,
nutrition bars and antioxidant beverages), and the increased skepticism about
the value of results from in vitro antioxidant assays may have an impact on
these claims.8 It may become less enticing for companies to make
such claims if a majority of the scientific community concludes that such data
are meaningless, or — as written in the editorial — that “‘antioxidant’ is a
marketing term of questionable health and analytical value.”1
—Stefan Gafner, PhD
References
- Harnly
J. Antioxidant methods. J Food Comp Anal. 2017;64(Part 2):145-146.
- The
“Rules of 5.” Journal of Ethnopharmacology website. Available at: www.elsevier.com/__data/promis_misc/jeprulesof5.pdf.
Accessed January 5, 2018.
- Guide
for authors. Fitoterapia website. Available at: www.elsevier.com/journals/fitoterapia/0367-326x/guide-for-authors.
Accessed January 8, 2018.
- Guidelines
for authors: editorial policy. Planta Medica website. Available at: www.thieme.com/media/ita/pubid-1019644585.pdf.
Accessed January 8, 2018.
- Kulbat
K. The role of phenolic compounds in plant resistance. Biotechnol Food Sci. 2016;80(2):97-108.
- Lattanzio
V, Lattanzio VMT, Cardinali A. Role of phenolics in the resistance mechanisms
of plants against fungal pathogens and insects. In: Imperato F, ed. Phytochemistry:
Advances in Research. Kerala, India: Research Signpost; 2006:23-67.
- Morales
LO, Tegelberg R, Brosché M, Keinänen M, Lindfors A, Aphalo PJ. Effects of solar
UV-A and UV-B radiation on gene expression and phenolic accumulation in Betula
pendula leaves. Tree Physiol. 2010;30(7):923-934.
- ORAC values might be passé, but antioxidant activity still
demands research, experts say. William Reed Business Media, Inc.; 2017.
Available at: www.nutraingredients-usa.com/Article/2017/08/15/ORAC-values-might-be-passe-but-antioxidant-activity-still-demands-research-experts-say.
Accessed January 2, 2018.
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