The exact mechanism of why this occurs is not well understood. The levels of other antioxidants, such as vitamins E and A, as well as the carotenoids lutein, zeaxanthin and lycopene do not appear linked with passive smoke exposure.
The issue of antioxidant nutrition is complex. Under certain conditions, antioxidants can be pro-oxidants. In its March 29, 2001 e-newsletter, the Competitive Intelligence Adviser (CIA) referred to an assessment by German researchers of the antioxidant properties of a variety of pure carotenes, (all-rac; dl ) alpha-tocopherol, flavonoids and indigoid.(ii)
The pro-oxidant tendencies of certain carotenes such as ÃŸ-carotene also were examined. The researchers inferred that this property likely was due to different head and tail chemistries as compared to astaxanthin and zeaxanthin. How relevant such findings are on human nutrition is harder to predict in that the tests generally are performed in vitro (test tube). - Claudia D. O'Donnell, Chief Editor
www.ajcn.org - The American Journal of Clinical Nutrition
www.imaginutrition.com - IMAGINutrition home page, click on CIA
(i) Albert van der Vliet, 2000. Am J Clin Nutr., Cigarettes, cancer, and carotenoids: a continuing, unresolved antioxidant paradox. J Sci Fd Agric. 72: 1421-1423.
(ii) Beutner, S., et. al., 2001. Quantitative assessment of antioxidant properties of natural colorants and phytochemicals: carotenoids, flavonoids, phenols and indigoids. The role of -carotene in antioxidant functions. J Sci Fd Agric. May 2001:81(6):559-568.