Asthma, oxidant stress, and diet

It has been suggested that the increased prevalence of atopy and asthma obs erved in many developed countries over the past 30 y is in part the result of a decrease in the incidence and severity of early childhood infections. The immunologic consequence of this phenomenon has been the expansion of T- lymphocyte populations away from the T-helper 1 (Th1) subset and in the dir ection of the Th2 subset. This leads to the creation of a cytokine-mediated propensity for the development of an intense inflammatory response in the airways, resulting in oxidative stress, airway tissue injury, and the devel opment of atopy and asthmatic symptomatology. Over this same period, there has been a decreased intake of dietary substances that contribute to antiox idant defense, and this appears to have contributed to the rise of atopy an d asthma. Studies evaluating the efficacy of these antioxidant substances i n the prevention of asthma and as adjuvants in the treatment of asthma are reviewed, and suggestions are made for the direction of future studies. (C) Elsevier Science Inc. 1999.