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Another Billion-dollar Industry that Sells the Illusion of Better Health

The untold stories from clinical trials of antioxidant supplements in cancer prevention

Jeremy Braude, Ph.D.
Mar 27 · 6 min read

If you asked within the biomedical research community whether it was a good idea to start taking antioxidant supplements, you would almost certainly be advised to proceed with caution. For several decades, researchers have acknowledged that a diet lacking in antioxidants is associated with higher rates of chronic disease. Many of us, however, are unaware that the supplements industry has been feeding off our fear of cancer, perpetuating the idea that their antioxidant products can provide us with protective effects. While there is evidence to support a protective role of higher dietary antioxidant levels when they are derived from whole foods, it has been largely assumed that the same benefits are obtained by supplementing your diet with antioxidants. What’s left is a deeply-rooted myth that antioxidant supplements are scientifically proven to fight cancer.

According to Allied Market Research, the antioxidant market was valued at around 2.9 billion dollars in 2015 and is expected to surpass 4.5 billion dollars by 2022. Now, if there were no risks associated with taking antioxidant supplements, you could argue that we should all take them ‘just in case.’ The problem, however, is that when you look at the clinical data, not only is their inconclusive scientific evidence surrounding the protective effects of antioxidant supplements, there are also several lines of research which suggest that they may increase your risk of developing cancer. Yet, despite this potential cancer risk, the “health” aisles in our supermarkets are filled with “natural” antioxidant products, which, by means of marketing, have been endowed with all the benefits of a balanced diet and no apparent side-effects. Although the idea of buying your health in a bottle of pills is appealing, when it comes to antioxidant supplements, this approach fails to appreciate our scientific understanding of antioxidant defences and their role in cancer prevention.


Every cell in your body needs antioxidants to survive because they form an integral part of your defence against free radicals. If left unchecked, free radicals, being chemically reactive molecules, can cause damage to the building blocks of your cells, including proteins, lipids and DNA. We typically think of free radicals as the result of exposure to external agents like ionising radiation (including UV rays from the sun), toxic chemicals or even viruses. But free radicals are also produced internally through regular cellular processes, such as the generation of energy in mitochondria.

When your body’s antioxidant defences cannot keep up with the level of free radicals, it leads to a state of oxidative stress in your cells. In this state, free radicals can cause genetic damage, which may accumulate over time. Since oxidative stress contributes to the transformation of healthy cells into genetically damaged cells, a defining characteristic of cancerous tumours, it follows that your antioxidant defences can influence the onset of cancer. So when the protective effects of an antioxidant-rich diet emerged from scientific studies, everyone was understandably excited by the prospect of reducing cancer risk through antioxidant supplements. But even before the clinical results had been determined, the word was already out — antioxidant supplements help fight cancer.

But what actually happened when antioxidant supplements were put to the test? In large-scale clinical trials performed around the world, researchers found that antioxidant supplements, including beta-carotin, retinol, alpha-tocopherol and vitamin C , generally had no effect on reducing the morbidity or mortality rates of cancer. Most of these trials looked at high risk populations, such as long-term smokers, older age groups, or people that had been diagnosed with cardiovascular disease or type 2 diabetes. The real surprise from these clinical trials, however, was that higher rates of cancer were sometimes observed in groups that were administered antioxidant supplements. Consequently, two of the trials were ended prematurely, the CARET study and the SELECT study.


When it comes to public health, the question has to be asked why the general population has been led to believe that antioxidant supplements can reduce cancer risk when clinical evidence suggests that the very opposite may be true. It’s not as if these trials have been locked up and hidden away. In fact, a comprehensive summary of the findings is publically available on the NIH website. Yet, I would go as far as saying that sales representatives and high-level managers for companies that sell antioxidant supplements are largely unaware of these studies. Of course, it wouldn’t be much of a sales pitch to let everyone know that there is a potential cancer risk associated with your health product. But, in my opinion, it’s just as dangerous that people don’t know about it all.

How can we explain this discrepancy in what is generally believed to be true and what has been clinically observed? To me, it comes down to a major conflict of interest in health promotion as there are always profits to be made from the latest health trends. And, perhaps fittingly, the supplements industry is grounded in the possibility of finding shortcuts to eating a healthy diet and exercising. It’s no coincidence that the potential health benefits of supplements are most heavily promoted alongside commercial products. While there is a scientific basis to most of these claims, they are usually case-control studies or cohort studies, which are limited to drawing correlations between population groups and disease outcomes. They do not, however, experimentally measure the effects of antioxidant supplements on cancer prevention.

It’s clearly an oversimplification to argue that antioxidant supplements definitively prevent cancer. In reality, supplements are going to affect individuals very differently depending on the situation. How healthy is the individual and are they currently at a high risk of developing certain cancers? Which antioxidants are being taken and at what dosage? And how do the individual’s diet and exercise choices influence their level of oxidative stress? Yet, despite all these limitations, there is no bigger buzzword in the health industry than antioxidants. It has become so powerful that it is almost synonymous with healthy living.


Although there is little commercial value in understanding the potential cancer risk of antioxidant supplements, researchers have sought to explain the surprising findings from the first generation of clinical trials. In animal studies, for example, it has been shown that N-acetylcysteine and vitamin E can increase the progression of lung tumours and promote metastasis in melanoma. Researchers have also highlighted that, in the same way healthy cells require antioxidants to combat free radicals, they may be even more important to the survival and growth of cancer cells. A major reason for this is that cancer cells typically deal with higher levels of free radicals than regular cells due to their aggressive metabolism. So while antioxidants, indeed, play a crucial role in the health of our cells, it’s also very plausible that, when available in high quantities from dietary supplementation, they can favour the growth of cancer cells. This is an important consideration for high risk populations, which are more likely to already possess a greater number of genetically damaged cells that have the potential to form tumours.


While there are certainly situations in which dietary supplements can offer health benefits, the billion-dollar antioxidant industry appears to be largely redundant in human health. The question we need to be asking is whether the potential benefits of an antioxidant cocktail are worth the scientifically established risks. Since we already know that sufficient levels of antioxidants can be obtained through a diet made up of whole foods, it doesn’t feel like there is any need for a shortcut. Perhaps the bigger question is whether it is fair to the general population that the supplements industry be allowed to push antioxidants as a health product, when many of the benefits are assumed but not necessarily proven. Although they are not blatantly lying about the underlying research into their products, they are certainly not advertising the whole scientific truth.

Dialogue & Discourse

News and ideas worth talking about. Fundamentally informative and intelligently analytical. Clarity and truth working against tribalism.

Thanks to Dialogue & Discourse

Jeremy Braude, Ph.D.

Written by

Using my experience in research and science communication, I aim to help people make better informed health decisions. http://theindustrialevolution.net/

Dialogue & Discourse

News and ideas worth talking about. Fundamentally informative and intelligently analytical. Clarity and truth working against tribalism.

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