Dietary modulation of the effects of exposure to 56 Fe particles B.M. Rabin a, * , J.A. Joseph b , B. Shukitt-Hale b , A.N. Carey b a Department of Psychology, University of Maryland Baltimore County, Baltimore, MD 21250, USA b Human Nutrition Research Center on Aging, USDA-ARS, Tufts University, Boston, MA 02111, USA Received 1 September 2006; received in revised form 8 May 2007; accepted 9 May 2007 Abstract On exploratory missions to other planets, astronauts will be exposed to galactic cosmic rays composed of protons and heavy particles, such as 56 Fe. Long-term exposure to these particles can cause cancer. However, there are significant uncertainties in the risk estimates for the probability of developing heavy particle-induced cancer, and in the amount of shielding needed to provide an adequate level of radi- ation protection. The results of this preliminary study, using a ground-based model for exposure to cosmic rays, show reduced tumor- igenesis in rats maintained on diets containing blueberry or strawberry extract prior to exposure to 56 Fe particles. Because the study was not initially designed to evaluate tumorigenesis following exposure to 56 Fe particles, additional research is needed to evaluate the effec- tiveness of strawberry and blueberry supplementation. However, the preliminary results presented in this study suggest that diets con- taining antioxidant phytochemicals can provide additional radiation protection on interplanetary voyages. Ó 2007 COSPAR. Published by Elsevier Ltd. All rights reserved. Keywords: Diet; Antioxidant; Tumorigenesis; Iron-56; Survival 1. Introduction As the manned exploration of space moves beyond the protection provided by the magnetic shield of the earth to include interplanetary travel, astronauts will encounter types of radiation that are not routinely encountered in low earth orbit (Badhwar, 1998; Letaw et al., 1989; Townsend et al., 1992). The radiation envi- ronment outside the magnetosphere is composed of galactic cosmic rays (GCR) which consist of protons and of particles of high energy and charge (HZE parti- cles), such as 56 Fe. There is a general consensus that a significant risk facing astronauts on exploratory missions to other planets is the possibility of developing cancer (Ball and Evans, 2001; National Academy of Sciences, 1996; Edwards, 2001). However, the level of the risk of carcinogenesis as a result of exposure to GCR involves significant uncertainties (Cucinotta et al., 2001). One way to reduce the risk of heavy particle-induced carcino- genesis is to increase the amount of shielding. However, the degree of uncertainty in the attempt to determine the risk of developing cancer means that unnecessarily large amounts of shielding may be used, which might make a mission to Mars economically infeasible (Wilson et al., 2001). A complementary approach to radiation protec- tion, in addition to shielding, would be to manipulate other factors that might influence tumor development. Among other effects on the health and functioning of the organism, oxidative stress and the production of reactive oxygen species have been linked to carcinogenesis (Kovacic and Jacintho, 2001; Oberley, 2002). Exposing organisms to ionizing radiation leads to oxidative stress and the produc- tion of free radicals. It is possible that the development of cancer following exposure to heavy particles similarly results from radiation-produced oxidative stress (Riley, 1994; Choudhury et al., 1998). If this is the case, then it would be possible to reduce the risk of carcinogenesis on missions outside the magnetosphere by treatments that reduce oxidative stress. One treatment that has been reported to be effective in reducing oxidative stress and the production of free 0273-1177/$30 Ó 2007 COSPAR. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.asr.2007.05.029 * Corresponding author. Tel.: +1 410 455 2430; fax: +1 410 455 1055. E-mail address: rabin@umbc.edu (B.M. Rabin). www.elsevier.com/locate/asr Advances in Space Research 40 (2007) 576–580