Orbiting Solutions for Better Post-Space Care

Exploring space is made possible with the help of astronauts. Space travel allows humans to gain a clearer understanding of our planet and the other celestial bodies that surround us. Consequently, astronauts are exposed to ionizing radiation at anywhere from 50 to 2,000 millisieverts (mSv).¹ Many units represent the doses of radiation, but the millisievert is a unit that specifically describes the degree of radiation biologically affecting humans, indicating health risk.² Acceptable levels of radiation exposure vary, depending on the condition of the individual or circumstances as some cancer patients are treated with radiation therapy.³ Ideally, one should not exceed exposure to 1 mSv annually.² 

On average, 1 mSv of ionizing radiation is equivalent to receiving three X-rays.^1,2 Therefore, at minimum, an astronaut would be exposed to doses of radiation that is equivalent to 150-6,000 X-rays. Exposure to high/continuous amounts of ionizing radiation can increase the risk of central nervous system decline, degenerative diseases, and cancer. Ionizing radiation is a high-energy process that essentially kicks electrons out of the matter that it strikes. It can be found in solar flare particles, radiation belt particles, and galactic cosmic rays. On Earth, we are protected by a large magnetic field called the magnetosphere.¹ However, astronauts are inevitably exposed to particles that induce ionizing radiation when passing through the magnetosphere.¹ 

In addition to ionizing radiation exposure, astronauts also experience loss of bone density during space travel. In an environment where gravity does not exist, along with the lack of counteracting forces against an individual standing up, astronauts are unable to exercise their bones and keep them in their “normal” conditions prior to space travel.⁴  In addition, the lack of impact from walking on a solid ground surface is lost due to floating in the microgravity environment.⁴ Similar to the effects of  leading a sedentary lifestyle on Earth, lack of exposure and consistent impact against the bones will lead to a decreased bone density.⁵

This poses a question: Are there any interventions or solutions that can improve the quality of life for astronauts? While there is no single straightforward method, multiple approaches could be used and combined to help astronauts mitigate the health risks of space travel. 

Firstly, their exposure to radiation could be limited. This solution is the most challenging, as ionizing radiation in space is inevitable, and equipment has not fully reached maximum optimization. Some examples of interventions include radioprotectors, radio modulators, radio mitigators, immune modulation, and supportive care for the aftermath of radiation. Radioprotectors are designed compounds given prior or during radiation, shielding molecules and tissue from indirect and direct damage that can be caused by ionizing radiation.⁶ Radiomodulators, on the other hand, act as natural antioxidants, combatting oxidation of cell membranes, and are incorporated post-radiation.⁷ Immune modulation consists of medications that are used for altering the body system.⁸ Immune modulation can either increase immune response, making immune cells more attuned to destroying cancer cells, or decrease immune response by suppressing the immune system.⁸

Another intervention that is currently being utilized is physical activity to help promote better bone health in astronauts, with devices that make exercise possible in the microgravity environment of space.⁴ In addition to exercise, studies have been conducted to show that proper nutrition can reduce  health risks associated with ionizing radiation exposure. For example, foods such as tomatoes, carrots, algae, salmon, and squash contain compounds called carotenoids.⁹ One specific carotenoid lutein is a retinal radioprotectant, a substance that protects the retina from radiation damage.⁹ Some other compounds such as polyphenols found in green tea and resveratrol found in grapes help with combatting oxygen ions and hydrogen peroxide, supporting mitochondrial activity.⁹ While these studies provide some insight into the implications of nutrition on combating oxidative stress, they need to be further explored in the clinical research space.⁹ Making more advancements in the field of nutrition with regards to individuals taking part in space travel could help find the missing pieces of the puzzle to help improve their quality of life after space travel.  

References:

1. NASA. (2017, April 13). Why Space Radiation Matters. NASA. https://www.nasa.gov/missions/analog-field-testing/why-space-radiation-matters/
2. Principles of Ionizing Radiation. (1999, September 1). Www.ncbi.nlm.nih.gov; Agency for Toxic Substances and Disease Registry (US). https://www.ncbi.nlm.nih.gov/books/NBK597565/
3. Lin, E. C. (2010). Radiation Risk From Medical Imaging. Mayo Clinic Proceedings, 85(12), 1142–1146. https://doi.org/10.4065/mcp.2010.0260
4. Risk of Spaceflight-Induced Bone Changes – NASA. (2024, October 23). NASA. https://www.nasa.gov/reference/risk-of-spaceflight-induced-bone-changes/
5. Manaye, S., Kaaviya Cheran, Murthy, C., Bornemann, E. A., Hari Krishna Kamma, Alabbas, M., Elashahab, M., Abid, N., & Arcia, A. P. (2023). The Role of High-intensity and High-impact Exercises in Improving Bone Health in Postmenopausal Women: A Systematic Review. Cureus, 15(2). https://doi.org/10.7759/cureus.34644
6. Montoro, A., Obrador, E., Mistry, D., Forte, G. I., Bravatà, V., Minafra, L., Calvaruso, M., Cammarata, F. P., Falk, M., Schettino, G., Vidhula Ahire, Noami Daems, Boterberg, T., Dainiak, N., Chaudhary, P., Baatout, S., & Mishra, K. P. (2023). Radioprotectors, Radiomitigators, and Radiosensitizers. Springer EBooks, 571–628. https://doi.org/10.1007/978-3-031-18810-7_11
7. Vasin, M. V., & Ushakov, I. B. (2020). Radiomodulators as Agents of Biological Protection against Oxidative Stress under the Influence of Ionizing Radiation. Biology Bulletin Reviews, 10(4), 251–265. https://doi.org/10.1134/s2079086420040106
8. Strzelec, M., Detka, J., Patrycja Mieszczak, Małgorzata Katarzyna Sobocińska, & Majka, M. (2023). Immunomodulation—a general review of the current state-of-the-art and new therapeutic strategies for targeting the immune system. Frontiers in Immunology, 14. https://doi.org/10.3389/fimmu.2023.1127704
9. Montesinos, C. A., Khalid, R., Cristea, O., Greenberger, J. S., Epperly, M. W., Lemon, J. A., Boreham, D. R., Popov, D., Gorthi, G., Ramkumar, N., & Jones, J. A. (2021). Space Radiation Protection Countermeasures in Microgravity and Planetary Exploration. Life, 11(8), 829. https://doi.org/10.3390/life11080829

Image References:

1. Hand drawn astronaut in spacesuit flying in the space with space rocket behind, cosmonaut in space. https://stock.adobe.com/search?k=astronaut