Many plant-derived chemicals that are called &quot;antioxidants&quot; by the popular press (e.g. catechins [1], anthocyanins [2], retinoids [3], etc.) have been shown to kill some types of cancer cells in vitro and in animal models, but <i>not</i> because they function as antioxidants per se. Instead, it seems that they modulate particular cell signalling pathways that regulate cell growth and survival just like other targeted cancer drugs [4]. In other words, the fact that these molecules can neutralize free radicals in vitro is irrelevant to their mechanism of action. Treating all of these diverse chemicals as one class, &quot;antioxidants&quot;, just muddies the waters.<p>In fact, there are even some cases where an &quot;antioxidant&quot; molecule selectively killed a type of cancer cell by <i>increasing</i> oxidative stress inside cells, the opposite of what you&#x27;d expect from the blanket label. For example, it was recently shown that high doses of vitamin C selectively kill a type of colorectal cancer cell, but the mechanism of action was actually that the cells take up the oxidized form of vitamin C via a sugar transporter that tends to be upregulated in cancer cells, and the vitamin C-derrived pro-oxidant caused an oxidative stress signalling cascade that led to cell death [5].<p>[1] <a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Catechin" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Catechin</a><p>[2] <a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Anthocyanin" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Anthocyanin</a><p>[3] <a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Retinoid" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Retinoid</a><p>[4] A corollary is that, like other drugs, each of these chemicals that is effective against some type of cancer probably won&#x27;t necessarily work against other types.<p>[5] <a href="http:&#x2F;&#x2F;science.sciencemag.org&#x2F;content&#x2F;early&#x2F;2015&#x2F;11&#x2F;04&#x2F;science.aaa5004" rel="nofollow">http:&#x2F;&#x2F;science.sciencemag.org&#x2F;content&#x2F;early&#x2F;2015&#x2F;11&#x2F;04&#x2F;scien...</a>