Regulation of physiological systems by nutrientsOpportunities for nutritional amelioration of radiation-induced cellular damage☆
Introduction
The closed environment and limited evasive capabilities inherent in space flight expose astronauts to many potential harmful agents (chemical contaminants in the environment and cosmic radiation exposure). Chemical contaminant exposure can be mitigated by changes in material composition and in air and water filtration systems. However, current power systems used to achieve space flight are incapable of supporting the weight requirements to fully shield the astronauts from cosmic radiation. Therefore, radiation poses a major, currently unresolvable risk for astronauts, especially for long-duration space flights. In fact, the National Aeronautics and Space Administration (NASA) has identified the health risks associated with exposure to radiation as one of the most serious limitations to long-term missions on the International Space Station or exploration missions to other planets such as Mars.1, 2, 3 The risk would be even greater for those undergoing multiple, sequential exposures because diseases such as cancer develop after multiple insults. If shielding is not an option, then other countermeasures must be developed to protect astronauts from galactic cosmic radiation (GCR) and the potential for disease induction. One potential route is through dietary modification.
To best address the possible roles nutrition may play in preventing the kind of physical and chemical damage that occurs with radiation exposure, it is first important to understand the types and sources of radiation to which astronauts and other people are exposed. Therefore, this review first describes radiation types, sources, and levels found from sea level to outside Earth’s atmosphere. The second part of the article describes the biological effects attributed to these types of radiation. Last, a description of some of the literature is provided, which suggests nutrition may be a determinant of how the human body responds to the kind of radiation prevalent in space and on Earth.
Section snippets
Radiation environment
Until people started exploring space, we had led rather a sheltered existence as far as exposure to ionizing radiation was concerned. We were protected by the magnetic fields of our solar system and Earth and by the Earth’s thick atmosphere. However, space outside the solar system is permeated by atomic nuclei that have gained very high velocities and thus have become highly ionizing particles known as galactic cosmic radiation. Our primary power source, the sun, is also a major source of
Tissues and systems affected by radiation
The possible detrimental effects of radiation in space have been considered since the inception of space flight. Astronauts are exposed to a number of serious risks that are not found in a typical occupational setting. For this reason, radiation protection limits are different for astronauts than for the public or other types of radiation workers. Limits were originally set to avoid acute effects and to limit any late-occurring effects of radiation (e.g., cataracts and cancer).
NASA sets career
Radiation effects and cellular responses
Biological molecules are susceptible to physical and chemical modifications whenever they are exposed to ionizing radiation.32, 33 Whenever a large-enough particle, such as iron, passes through a cell, it is capable of physically damaging molecules. This becomes critical in the case of DNA, resulting in mismatch repair and chromosomal rearrangement in which the DNA strands do not reattach to the correct corresponding piece of DNA, or segments of DNA are deleted altogether. The other form of
Nutritional interventions to reduce radiation-induced cancer
An obvious recommendation to reduce the oxidative damage that occurs from radiation exposure is to consume additional amounts of antioxidants. Many natural antioxidants, whether consumed before or after radiation exposure, are able to confer some level of radioprotection.53 A general review of antioxidants and their effect on reactive oxygen compounds has been provided by Fang et al.45 Therefore, the primary focus of this review is on specific compounds that have been evaluated in humans,
Relationship to Earth-based nutrition
On Earth we are exposed to only limited amounts of the type of radiation to which astronauts are exposed. However, as discussed in this article, while on Earth we are still exposed to radiation sources, with the quantity and risk associated with that exposure being dependent on the geographic location, elevation above sea level, and our profession. In addition, many individuals are exposed to radiation for diagnosis and treatment of disease. Therefore, it is very important that we understand
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Support was provided by the National Space Biomedical Research Institute (NPFR00202), NIH (CA61750, CA82907), and NIEHS (P30-ES09106).