Too high a dose of antioxidants can block DNA repair

A reminder of the importance of taking a physiological approach based on objective evidence came in the form of an important paper just published in the journal Stem Cells. The authors report unexpectedly finding that too high a dose of antioxidants can increase damage to DNA. They initially wanted to see how to protect stem cells from oxidative damage:

"Stem cell cytogenetic abnormalities constitute a roadblock to regenerative therapies. We investigated the possibility that reactive oxygen species (ROS) influence genomic stability in cardiac and embryonic stem cells."

They were surprised to observe that chromosomal abnormalities and DNA damage appeared when the ROS inside cardiac stem cells were sharply decreased by high-dose antioxidants:

"Quantification of DNA damage in cardiac stem cells and in human embryonic stem cells revealed a biphasic dose-dependence: antioxidants suppressed DNA damage at low concentrations, but potentiated such damage at higher concentrations."

How could too high a dose of antioxidants cause this effect?

"High-dose antioxidants decreased cellular levels of the ATM (ataxia-telangiectasia mutated) and other DNA repair enzymes, providing a potential mechanistic basis for the observed effects."

This is an immensely important key point for clinical practice and self-care alike. There are innumerable biological biphasic phenomena. Except for aggressive short-term interventions justified by acute indications, it's important to stay within a physiological 'window' with everything from antioxidants to hormones. This can be determined on an individual basis by the appropriate objective tests.The authors' conclusion is well worth bearing in mind:

"These results indicate that physiological levels of intracellular ROS are required to activate the DNA repair pathway for maintaining genomic stability in stem cells. The concept of an oxidative optimum for genomic stability has broad implications for stem cell biology and carcinogenesis."