Prooxidant Behavior

The ability to quench singlet oxygen, porphyrin triplet energies, and free radical reactions are examples of the antioxidant nature of carotenoids. An in vitro study showed that, at low partial pressures of oxygen (pO2), ¡-carotene consumed peroxy radicals efficiently as in: CARL + ROO-! CAR/+ + ROO. At higher pO2, however, ¡-carotene became a prooxi-dant through autooxidation. Recently, experiments in intact murine normal and tumor thymocytes showed that ¡-carotene lost its antioxidant potency at higher pO2, and the effect was more pronounced in tumor cells. It is still unclear, however, whether some effects of carotenoid behavior at higher pO2 are due to prooxidant activity or simply lack of antioxi-dant ability. Prooxidant effects of ¡-carotene have also been used to explain results from intervention trials of ¡-carotene supplementation in diets of smokers or individuals suffering from asbestosis where the incidence of carcinogenesis was higher in those individuals taking the ¡-carotene supplement. Generation of deleterious oxidation products from ¡-carotene reaction with reactive oxygen species in tobacco smoke or as a result of asbestosis has been proposed. Interference with retinoid signaling was also considered. However, whether those effects were due to prooxidant behavior or lack of antioxi-dant ability is still unclear.

Breaking Bulimia

Breaking Bulimia

We have all been there: turning to the refrigerator if feeling lonely or bored or indulging in seconds or thirds if strained. But if you suffer from bulimia, the from time to time urge to overeat is more like an obsession.

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