Astronauts immune system responses are altered following spaceflight, and that can potentially be contributed to an increase in stress hormones (Narici, 2015). When astronauts are on the ISS (International Space Station), they are subjected to radiation and low g-forces because of the high altitude. Astronauts have been shown to suffer a myriad of issues upon returning to the Earth’s surface. The question then becomes: What can be done to mitigate some of the issues that the Astronauts face?
Large amounts of ionizing radiation have been proven to harm humans, and there has been evidence correlating it to cancer (Brenner et al, 2003).
With the increase in altitude above the Earth’s surface the radiation that the human body is exposed to is much greater, this is due to the lack of atmosphere to filter out the harmful radiation since the ISS altitude is 248 miles above the Earth’s surface (Narici et al., 2015). While small amounts of radiation are needed for evolution, the large amounts that humans are exposed to at the high altitude is extremely dangerous to their overall long-term health.
Radiation on the ISS comes from two major external sources which is the GCR, galactic cosmic rays, and SPE, solar particle events (Narici et al, 2015). These two constant sources of radiation impose severe health risks on astronauts, especially when the larger radiation particles smash through the DNA of the astronaut and cause DNA mutation. The mutated cells then must be disposed of by the body and its natural killer cells. However, bear in mind that the Astronaut is in a perpetual sympathetic dominant state, that does not allow the body to truly enter a repair state.
This means the body has a harder time removing the problem cells and increases the risk of cancer if those cells are not removed.
Although NASA’s radiation limits only allow a 3% cancer fatality probability, in studies examining the long-term effects of the radiation on the astronaut’s post-exposure it was found the cancer risk due to prolonged exposure to be significantly higher, nearing 50% risk of developing cancer (Cucionetta, 2014). This increased cancer risk can be related to the amount of time the astronaut was exposed to the radiation. The long-term exposure must have damaged the integrity of immune system cells, making the cells vulnerable to overgrowth, or out of control growth, resulting in cancer. With the constant sympathetic dominant state that the body is in, the lack of proper gut bacteria replacement, and the extremely sterile environment the Astronauts are in the body is incapable of properly initiating an immune system response to the cancer cells. It has been shown that the gut has “70-80% of the body’s immune cells” (Furness, Kunze, & Clerk, 1999).
Various factors impact the human during spaceflight including microgravity, physiological stress, isolation, diet changes, and disrupted circadian rhythms (Crucian et al., 2013). The physical stressors stated put the Astronaut in a sympathetic dominant state, that doesn’t allow the body any chance to enter a parasympathetic dominant state and heal the body. To determine how much radiation astronauts aboard the ISS are being exposed to, a radiation monitoring system was installed in the Zvezda module of the ISS. Daily measurements were taken from the system to assess the radiation exposure to astronauts aboard the space station (Lishnevskii, & Benghin, 2014). The results of the test showed that the radiation on board the ISS was highly variable and could not be controlled. The results also showed that the majority of bulk leukocyte subsets were unaltered during spaceflight but changed following landing. This was attributed to the significant change in the gravitational force, putting stress on the cells (Crucian et al., 2013). For astronauts going on frequent space-flights, the long-term immune system dysregulation paired with the radiation exposure, microgravity, changes in g-force, and altitudes created a risk for negative health effects.
The radiation, g-forces, and altitude by themselves do not cause the issues the body shows upon return to Earth. The change in the bodies response as it tries to reach an internal homeostasis given the new environment are shown within the first several weeks of their stay on the ISS and the changes are the bodies way of responding to the environment to keep the Astronaut alive. While some immune cells are heightened by the changes in altitude during space travel, other immune cells get depressed (Feltman, 2014).
When radiation pierces a cell and effects the DNA structure of that cell, the Astronauts Natural Killer (NK) cells would normally get rid of the damaged cell to protect the body. However, given the effects of lowered g-force and the high altitude the body’s “lymphocytes, white blood cells in the immune system that are called upon to destroy infection, show a reduced function after short-term space flight” (Faulk, 2016). While on Earth the body naturally gets rid of billions of cancer cells a day, but when the body’s natural system is disrupted and put under larger amounts of stress, such as the chronic stress of being in space, the body’s immune response weakens as a result. The chronic stress puts the Astronaut in a sympathetic dominate state, which will cause the immune system to not function as it should and the body not to repair itself properly.
Given the information available that shows the immune system’s response is controlled by the Autonomic Nervous System (ANS), it can be concluded that by ensuring lower stress levels and proper prayer and meditation can instigate a parasympathetic dominate state the will increase the immune systems strength and allow the body to heal. From the information gathered, if the Astronauts have a strong immune system the risks of cancer development and fungal, viral, and bacterial infections causing a problem for the Astronauts decreases. The natural supplementation, healthy diet, and good probiotics can increase the body’s immune system and should be considered for future spaceflights to help with mitigation of the overall disease problems that could be encountered.