Antioxidant is one of the many buzzwords of health and nutrition, slapped across supplement labels and touted for more benefits than you can count on all digits. For good reason, you might think: Antioxidants play crucial roles in protecting our cells from harm, and harm can lead to cancer. So surely, the more the merrier? Evidence for this idea is shady, particularly when it comes to cancer, and now here is some more suggesting the contrary: A new study has found that antioxidant supplementation can actually increase the spread of skin cancer in mice.
Using human melanoma cells, the team may have identified a possible underlying mechanism for this effect, although it’s far too premature to advise people, especially cancer patients, on their antioxidant intake solely based on these early results.
First things first: How many people drowning themselves in green tea know what an antioxidant is? You’re probably aware that you can obtain them from your diet, but our body produces its own, too. That’s because during normal metabolism, our body generates highly reactive, oxygen-containing molecules as byproducts. Now, these actually have a role in the cell, but in excess they can cause problems, running riot and damaging important structures like proteins and DNA. Broken DNA, as we all know, is not a good thing: left unfixed, it can lead to cancer.
So it seems logical that, as molecules that protect from damage, increasing intake of antioxidants should exert beneficial effects on the body, like cancer prevention. Indeed, this is the view held by many, yet studies have turned out conflicting results. For example, one study found a slight protective effect of vitamin E supplements on breast cancer risk, but another found that selenium and vitamin E may actually increase the risk of prostate cancer.
Some animal studies have also not yielded supporting results. Some in mice, for example, found that antioxidants can drive the progression of lung cancer. But this had been the only type of cancer in which such a relationship had been investigated, so researchers decided to see whether antioxidants have the potential to alter progression of other types.
For the present study, the team from the University of Gothenburg in Sweden focused on melanoma, or skin cancer. They started off with a mouse model of this cancer, which spontaneously develops tumors that resemble those in human patients. After spiking their water with the antioxidant N-acetylcysteine, a widely used antioxidant, the team observed that the number of metastases – tumors that have spread from the primary site – in the lymph nodes was double that of control mice. The number and size of primary tumors, however, seemed to be unaffected.
Next, they used human skin cancer cells in a dish and exposed them to N-acetylcysteine again, as well as a similar antioxidant to vitamin E. Supporting the previous findings, they found that the cells did not increase in number, but that their migratory and invasive properties were enhanced. Examining this relationship further, the scientists found that the antioxidants seemed to be activating a protein that helps regulate the cell’s structural scaffold, called RHOA. And when they blocked this molecule, the researchers no longer observed an increase in invasiveness in the presence of the antioxidants. These findings have been published in Science Translational Medicine.
The study is certainly interesting, but by no means do these findings necessarily apply to other yet uninvestigated cancers, or perhaps even what happens in the human body. Still, evidence that antioxidant supplements may not match the hype is mounting.