There’s no doubt that vitamin C (a.k.a. ascorbic acid) is good for you in general, but via Effect Measure comes news that in one very particular circumstance it might play a role in how hexavalent chromium causes cancer.

Work done by Anatoly Zhitkovich and his colleagues and students at Brown University has revealed that chromate carcinogenicity depends on the failure of a repair system for DNA damage, the kind called DNA mismatch repair. Here is the provisional picture as assembled by that group. Ascorbate is a strong potentiator of chromate metabolism from the VI form to the III form.

As the article also explains, it’s the VI (hexavalent) form that gets into the cell and the III form that causes cancer. The real lesson here, though, has little to do with cancer or the particular chemicals involved and a lot to do with how we think about the chemistry that happens within our bodies. This is an excellent example of how studying a single substance – hexavalent chromium – by itself can cause us to miss or misunderstand how it works within the actual chemical milieu we care about. Forms and combinations of chemicals do matter, so we can’t just say that all pills containing the same active ingredient – e.g. brand name vs. generic – are really the same. We have to weigh the specific evidence about how absorption rates and interactions and so on might actually influence results.