FWD 2 Journals Skeptical of Antioxidant Assays | HerbalEGram | January 2017

HerbalEGram: Volume 15, Issue 1, January 2018

Scientific Journals Increasingly Skeptical of Antioxidant Research


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 re-submit 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 (Figure 1) over the past two decades.


Figure 1. Number of Papers with the Term 'Antioxidant Activity' in Their Title or Abstract Listed in PubMed, 1975-2015.

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

  1. Harnly J. Antioxidant methods. J Food Comp Anal. 2017;64(Part 2):145-146.
  2. The “Rules of 5.” Journal of Ethnopharmacology website. Available at: www.elsevier.com/__data/promis_misc/jeprulesof5.pdf. Accessed January 5, 2018.
  3. Guide for authors. Fitoterapia website. Available at: www.elsevier.com/journals/fitoterapia/0367-326x/guide-for-authors. Accessed January 8, 2018.
  4. Guidelines for authors: editorial policy. Planta Medica website. Available at: www.thieme.com/media/ita/pubid-1019644585.pdf. Accessed January 8, 2018.
  5. Kulbat K. The role of phenolic compounds in plant resistance. Biotechnol Food Sci. 2016;80(2):97-108.
  6. 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.
  7. 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.
  8. 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.

† ORAC: Oxygen Radical Absorbance Capacity; DPPH: 2,2-Diphenyl-1-picrylhydrazyl; TEAC: Trolox Equivalent Antioxidant Capacity; FRAP: Ferric Reducing Antioxidant Power