More research is needed into antioxidants found in plants, which may actually aggravate health conditions rather than benefiting people who eat them. Specifically, quercetin and ferulic acid have been shown to aggravate kidney cancer in severely diabetic laboratory rats, according to a study in the Journal of Agricultural and Food Chemistry.
Kuan-Chou Chen, Robert Peng, and colleagues note that vegetables, fruits, and other plant-based foods are rich in antioxidants that appear to fight cancer, diabetes, heart disease, and other disorders. Among those antioxidants is quercetin, especially abundant in onions and black tea, and ferulic acid, found in corn, tomatoes, and rice bran. Both also are ingredients in certain herbal remedies and dietary supplements. But questions remain about the safety and effectiveness of some antioxidants, with research suggesting that quercetin could contribute to the development of cancer, the scientists note.
It’s always struck me as odd that you would want to ingest extra antioxidants anyway, given that oxidising agents are at the front-line of immune defence against pathogens and cancer cells. This work vindicates that outlook at least in a small lab study of two commonly supplemented antioxidants under certain conditions (is that enough qualifiers for one sentence?). Suffice to say that taking antioxidant supplements whether derived from plants or not may not necessarily be good for your health if you already have health problems.
Hsieh CL, Peng CC, Cheng YM, Lin LY, Ker YB, Chang CH, Chen KC, & Peng RY (2010). Quercetin and Ferulic Acid Aggravate Renal Carcinoma in Long-Term Diabetic Victims. Journal of agricultural and food chemistry PMID: 20669956