Antioxidant Supplements – Maybe Not Such A Good Idea

We are barraged with advertisements that promote that everyone, including people diagnosed with cancer; add antioxidants to their diet and their regimen of supplements.  However, taking antioxidants might not be a very good idea!  

Multiple studies have reported that in mice models antioxidant supplements promote cancer tumor growth and metastasis.  These studies showed that antioxidants like those many of us take as dietary supplements may encourage tumor growth and metastasis! 

Yes, you read that correctly, antioxidants may support the progression of your cancer.  People with cancer should reconsider taking any antioxidant supplements or foods with added antioxidants.

Antioxidants might not be helping you, they may be harming you! 

Large studies have suggested that people with cancer and people with an increased risk of cancer should avoid taking antioxidant supplements.

It had long been hypothesized that antioxidants might be able to protect against cancer because they neutralize reactive oxygen species (ROS) that can damage DNA. In laboratory and animal studies, the presence of increased levels of exogenous antioxidants has been shown to prevent the types of free radical damage associated with cancer development.  However, there have been multiple large randomized, placebo-controlled prevention clinical trials that have failed to substantiate this idea.

In some instances of the large clinical trials, the trials have been terminated because the participants receiving antioxidants had a significantly higher incidence of cancer than those who did not receive the antioxidants!

To investigate how antioxidants might affect cancer progression, Martin Bergö, Ph.D., of the University of Gothenburg in Sweden, led a 2014 study in mouse models of human lung cancer. Dr. Bergö and his teams found that adding the antioxidants N-acetylcysteine (NAC) or vitamin E to the diet of mice with small lung tumors substantially increased the number, size, and stage of the tumors.

Additional work by Dr. Bergö showed that the NAC and vitamin E reduced levels of ROS and DNA damage in cancer cells, and virtually eliminated expression of the gene p53—a tumor suppressor gene that is typically activated by DNA damage.

According to Dr. Bergö, these findings provide a plausible explanation for why the male smokers in the trial who received antioxidants in the Alpha-Tocopherol, Beta Carotene Cancer Prevention Study in Finland had a higher incidence of lung cancer than those who received a placebo. The most straight forward explanation, Dr. Bergö said, is that when the trial recruited patients, many of them had small, undiagnosed lung tumors, which progressed more rapidly when the smokers were given antioxidants.

In their most recent study, published October 7 2017, in Science Translational Medicine, Dr. Bergö’s team examined the effects of antioxidants on melanoma.  They found that supplementation of drinking water with NAC doubled the number of lymph node metastases in their subject mice.  They also found that in human melanoma cell lines, the treatment with NAC and the soluble vitamin E analog (Trolox) didn’t affect cell proliferation, but it did increase the cells’ ability to invade and migrate.

Another study, found that antioxidants promote cancer metastasis in mouse models of melanoma, was published October 14, 2017, in Nature.  The research team headed up by Sean Morrison, Ph.D., of the University of Texas Southwestern Medical Center found the levels of oxidative stress were higher in circulating cancer cells than in cancer cells in primary tumors. Oxidative stress interfered with the formation of metastatic tumors. Treating these mice with antioxidants decreased oxidative stress in the circulating cancer cells and increased their ability to metastasize.

Dr. Morrison said in a press release, “Administration of antioxidants to the mice allowed more of the metastasizing melanoma cells to survive, increasing metastatic disease burden,”  The findings support the idea that antioxidants, by reducing oxidative stress, benefit tumor cells more than they benefit normal healthy cells, Dr. Morrison added.

He stated that these results support the idea that treating cancer patients with pro-oxidants as opposed to antioxidants might be a way to prevent metastasis.

A commonly used cancer drug, methotrexate has pro-oxidant properties. The drug works by inhibiting an enzyme called dihydrofolate reductase (DHFR), which plays a key role in the metabolic pathways that produce glutathione, as well as the pathways that produce new DNA bases. By blocking DHFR, methotrexate interferes with DNA replication and increases oxidative stress.

Based on the available evidence, despite this negative data coming from mouse models, we should be concerned about the aggressive marketing of antioxidants to cancer patients. The data strongly suggest that using antioxidants “could be really dangerous in lung cancer and melanoma, and possibly other cancers,” said Dr. Bergö.  He added, “Because there’s no strong evidence that antioxidants are beneficial, cancer patients should be encouraged to avoid supplements after they have a diagnosis.”

Are you taking antioxidants?  Perhaps you should cut them out of your supplement protocol? 

https://www.cancer.gov/news-events/cancer-currents-blog/2015/antioxidants-metastasis