Antioxidant evidence is very weak, concludes review

By Eliot Beer

- Last updated on GMT

Researchers should 'sum up the level of evidence available rather than test another new antioxidant extracted from a different fruit'. ©iStock/brozova
Researchers should 'sum up the level of evidence available rather than test another new antioxidant extracted from a different fruit'. ©iStock/brozova

Related tags: Oxidative stress, Reactive oxygen species, Antioxidant

Evidence for the beneficial effects of antioxidants is very weak, and researchers should work harder to understand the mechanisms behind oxidative stress, an academic review has concluded.

The review, published in the British Journal of Pharmacology​, looked at the evidence behind the oxidative stress (OS) theory of disease, and some of the issues with the model. They found it to be significantly lacking for the nutrients present in a range of fruits and vegetables.

Viewing the OS theory of disease from different theoretical perspectives developed in epistemological research, the theory comes out significantly weaker than many other pathogenic theories​,” wrote the authors.

This might explain why the translational shortcut of this theory, antioxidant therapy, has failed so often and has never shown enough evidence to be incorporated in guidelines, approved by regulatory agencies and recommended and reimbursed by health insurance systems basing their decisions on [evidence-based medicine] criteria​,” they added.

A stressed narrative?

The authors describe how the OS theory has become a powerful narrative: “The fight between good and evil, antioxidants preventing ageing like the Holy Grail or acting like shields against ROS, an imagery and wording often used even by scientists in their review articles or presentations​.”

But despite the strength of the narrative, the mechanisms behind reactive oxygen species (ROS) are usually contained within a “black box​” which is applied to a list of diseases “so long to include practically all of them​” – making it very hard to describe the actions of ROS.

We have seen that this is in part due to the technical difficulties of measuring ROS, an essential step to make a claim of a ROS-mediated disease, which is complicated by the large number of analytical techniques and analytes that have been used to make such claims​,” the authors wrote.

Trying to aggregate a plurality of diseases where different ROS are generated in different tissues by different sources may have aggravated the problem​,” they added.

They also noted potential issues with side-effects: “When taking the theory of OS from the bench to the bedside using antioxidants as drugs we are adding the problem that most of them, more than most drugs, will have off-target effects, or that ROS may have physiological functions beyond their toxic effects​.”

Open data and causal relationships

To improve the standard of evidence around oxidative stress and antioxidants, the authors have several concrete suggestions.

First they advocate the development of international collaborations, including open data and a Cochrane-style collaboration for preclinical studies.

Second, they suggest a priority should be to “address the key question of how to demonstrate that OS is a causal component in disease X​”.

botanical plant herbal science research
©iStock

Finally, they call for researchers to “sum up the level of evidence available rather than test another new antioxidant extracted from a different fruit, where a plethora of antioxidants from other sources have already been studied​”.

Funding agencies need to encourage scientists to take the hardest route rather than go for the easy publication and the conventional wisdom of the dominant group​,” wrote the authors.

Only critical, honest and out-of-the-box analysis of redox research will lead to the identification of redox pathways involved in pathologies and only then will innovative therapeutics be emerging​,” they concluded.

 

Source: British Journal of Pharmacology

Published online ahead of print, doi: 10.1111/bph.13544

The oxidative stress theory of disease: levels of evidence and epistemological aspects​”

Authors: Ghezzi, P.; Jaquet, V.; Marcucci, F.; Schmidt, H.H.H.W.

Related topics: Research

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2 comments

Prove it or lose it

Posted by Ken,

An antioxidant theory of disease is going a bit too far in my opinion. It was and remains a hypothesis, albeit, one so often repeated that consumers and uncritical thinkers have come to believe in it. But contrary to the supposition of Telekinetic, the review was written by scientists at 3 of Europe's best universities — not by pharmaceutical companies. The real propaganda is the repeated belief that an antioxidant reaction in a petri dish can explain the benefits of a dietary supplement or food without having established that the biochemical end-products in a living organism make any difference to outcomes of health or disease. When ROS are an essential armament of the immune system in protecting the body against viruses, pathogenic bacteria, and tumor cells, as well as part and parcel of the body's repair mechanisms, the idea of taking antioxidants becomes more about marketing and profits than anything else.

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More Pharmaceutical Propaganda

Posted by Telekinetic,

Once again, the pharmaceutical Ministry of Propaganda attempts to refute the brilliant work of Nobelists like Linus Pauling (2X) and others who have conclusively and clinically proven the anti-aging efficacy of natural and synthetic antioxidants. Drug companies that provide customers with compounds like Vioxx think they are providing safe medication despite the 60,000 deaths in a class action suit against the makers of Vioxx was settled in favor of the victims. My personal experience with antioxidants is that they work and are not placebos.

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