Host (Courtney Beasley): Houston, we have a podcast. Welcome to the official podcast of the NASA Johnson Space Center, episode 370, Spaceflight Adaptation. I'm Courtney Beasley, and I will be your host. Today on this podcast, we bring in the experts, scientists, engineers, and astronauts, all to let you know what's going on inside the world of human space flight, and more. From the early days of human space flight, we have known that microgravity and being in space in general would have impacts on the human body. Medical specialists have monitored our astronauts from the beginning, studying how the body reacts, adapts, and changes going to space and returning to earth. Today we're going to talk about some of those changes and some of the practices that our flight surgeons and other medical professionals here on the ground do to help astronauts mitigate the impacts on the human body during human space flight. And here to tell us all about it is NASA's Chief Health and Medical Officer, Dr. J. D Polk. Let's get started. Host: All right, Dr. Polk, welcome to Houston. We have a podcast. J.D. Polk: Thanks, Courtney. Glad to be here. Host: We're happy to have you. I wanted to start off by getting to know a little bit more about you. Can you tell me where you went to school and did you always know that you wanted to be a doctor? J.D. Polk: Oh, well, that's a pretty loaded question. It's probably easier to tell you where I haven't gone to school. Uh, I actually, uh, you know, I did my undergrad, started out in Dayton at, uh, Wright State, actually even before that. Did an associate degree in, in Dayton and physical therapy assisting. And, uh, just kind of kept working my way up the ladder, uh, if you will. Um, and then, uh, did, uh, my bachelor's in science in New York. Then, uh, went to medical school out at, uh, AT Still University in Missouri. Um, did a master's in science at American Military University. Did a master's in Medical Management at University of Southern California. Did another doctorate in aviation and space at Oklahoma State, et cetera, et cetera, et cetera. So, uh, but, um, board certified in emergency medicine and board certified in aerospace medicine. And, uh, did a lot of my clinical training, uh, in Cleveland, Ohio, uh, and was the, the chief of lifeline before I got into the, uh, space business, if you will, and got into it a little bit, uh, uh, you know, through the Air Force. Actually, I was in the Air Force Reserve and, uh, one of our assignments was to cover search and rescue for the space shuttle missions. And that's actually how I got introduced to the whole aerospace medicine in NASA. And then, uh, vectored from emergency medicine to aerospace and was a flight surgeon in the Air Force. The whole works and the rest is history. Uh, I kept, uh, working my way up the ladder and I think, I think, 'cause I'm the only one willing to do a budget, I kind of, uh, you know, kept getting promoted, uh, <laugh> on the medical side. Host: Well, you kind of talked about it already about your path to NASA, but when did you start here at NASA? J.D. Polk: Oh, golly. I think I started initially as a contractor supporting NASA in 2001, um, and then, uh, converted to a civil servant in 2004. Um, uh, but then I took, I shook, took a short break from NASA to be, uh, the Assistant Secretary of Homeland Security, um, and deputy assistant Secretary of Homeland Security. Uh, and then went on to be the assistant secretary and then went to be a dean of a medical school. Uh, and then came back to NASA, uh, especially as we began building all the new vehicles and the new programs with commercial crew and, and Artemis and, uh, have been, uh, the chief medical officer for, uh, for the agency. This is going on my ninth year, which sounds kind of, you know, I can't believe it's been that long. It's gone really quickly. Host: They say time flies when you're having fun. That must be it, it does, J.D. Polk: You get older for me, trust me, as you get older, it keeps rattling by faster and faster. Host: Can you give us an overview of what your position is here at NASA? What's your day-to-day like? J.D. Polk: Yeah, Sure. We, you know, at headquarters we formulate a great deal of healthcare policy, but also oversight of the, the 10 centers at NASA and the healthcare that they provide. But we take care of not only the NASA workforce, the entire NASA workforce, uh, throughout, uh, the agency, and to make sure that the, uh, healthcare and the, the policy to execute that healthcare and taking care of our worst workforce is put into place. But we also work on the, uh, the healthcare of the astronauts and making sure that the astronauts are healthy for all of their space missions. Uh, but we're also involved in the, uh, human factors and human systems integration of, uh, spacecraft and vehicles. And so developing the standards, uh, that are going into, um, how those vehicles are developed to support the astronauts on those missions. So it's, it's, uh, you know, a lot of different spheres that we get involved in, and including the human research element, uh, working with our partners at the Human research program, uh, to decrease the risks for human space flight as we go. Um, but there's also another little element where we work to make sure that those things that we develop or innovate for space flight also, uh, have some kind of on, uh, contribution to the ground in healthcare as well. And to see where those things can be, uh, developed, uh, to help, uh, you know, in areas like third world countries and others that might not, uh, um, you know, be able to do the same healthcare that we do in the United States, but use those technologies that we develop in space flight to that end. Host: That's really neat, and we will get into some of those benefits for here on earth later in our conversation. But I wanted to go ahead and start talking a little bit about the physical challenges of humans in space. Um, so I just wanted to see what some of the most significant health challenges astronauts face during long duration missions are. J.D. Polk: Yeah, probably the, uh, the elephant in the room is radiation. That's the one that everyone thinks about. And there's different types of radiation. There's the, uh, solar radiation, uh, that you get from the sun. There's radiation that's trapped, uh, in the magnetic sphere of the, of the earth. Uh, and there's what's called galactic cosmic radiation. That's, that's always a cool word, uh, even to say. But that's, uh, high energy transfer particles from outside our solar system, like if a star explodes and a neighboring solar system or another, uh, galaxy, and then starts zipping through those particles, zip through our, uh, our solar system. And so it's, uh, those, that's probably the elephant in the room. Then the, the microgravity challenges themselves, bone loss from microgravity, um, and then that fluid shift up into the head and thorax, uh, can cause changes in both, uh, vision, uh, and what we believe is, uh, some elevated intracranial pressure. But it's, it's hard to, to delineate whether how high that pressure is, because normally we do that on the ground with a spinal tap. Uh, and that would be a pretty messy procedure on orbit. So, uh, we've mostly been following that through what's called ocular coherence tomography, which is a fancy word for a scan that looks at the back of the eye to look at the edema and the, uh, or swelling that occurs in the back of the eye and astronauts. And, and so there's, uh, several different things that occur and, and there are other risks. Uh, we've recently seen clots in what, uh, what's called the internal jugular vein. Um, and that's a pretty risky thing if you think about when you fly on an airplane for a long time. And most people have heard the term DVT or, or deep vein thrombosis, uh, which you might get in your calf from a long airplane flight. Uh, astronauts gets, uh, are at risk for that, but not in their calf. They're actually at risk for it up in the, uh, the upper neck. And so it's, uh, due to that fluid shift and things that occur, and of course, muscle changes and neuro vestibular changes too. Uh, almost every organ system in the human body is affected in some way by microgravity and some of the challenges with space flight. Host: So how do you kind of track and check on those effects while these astronauts are in on orbit? J.D. Polk: Yeah. The flight surgeons do several things. They have, uh, a weekly PMC, which is a private medical conference. Uh, think about, uh, you know, like a telemedicine checkup with your doctor on how you're doing. But we also do intermittent exams, uh, including EKG, and like we talked about, the OCT that scan in the back of the eye, as well as ultrasound and even blood work, um, on a routine basis, uh, just to make sure that the astronauts are, are doing well and healthy. We also get, uh, feedback from the exercise that they do and their exercise regimen. Uh, they also put into, uh, the computer, uh, when they've had to take, uh, medications, things that you and I might just go to the medicine cabinet for at home, like Tylenol or Advil. We like to kind of keep track of that to see how they're doing on orbit, if they've got musculoskeletal, uh, issues or, or pain and things of that nature. Uh, you and I probably don't do that at home, uh, but, uh, we're a little bit more stringent on keeping track on how their health is going on orbit, uh, and even their nutrition, how many calories they're consuming, um, and how they're doing generally. And then, uh, they also have what are called private psychological conferences with the, uh, psychiatrist and psychologist, uh, to make sure that they're, they're tolerating, uh, the long duration mission well, uh, or even the short duration mission well, and, uh, that's one of the ways that we just make a, a kind of a holistic assessment to make sure that they're doing well physically, but also mentally, um, and that, uh, they're, uh, they're doing well for their space flight and, and enduring those challenges that can occur. Host: You mentioned exercise, which I know is a huge factor in keeping astronauts in shape and in great health on orbit. Are there other mitigating factors taken to help astronauts adapt? J.D. Polk: Yeah, you know, exercise is one of those things that's, uh, very interesting for us. Not only do they have aerobic exercise that they do one hour a day, but they do anaerobic exercise like, uh, resistive exercise, what we would call weightlifting on the ground. But of course, in microgravity, we don't really call it weightlifting. So it's, uh, providing resistance there. But one of the feedback that we've gotten from the astronauts is that not only does it help them physically, uh, but mentally as well, that the exercise, uh, uh, helps 'em, uh, you know, probably with some dopamine surge and other reasons for it. But they, they feel better mentally after exercising. Uh, and of course, they do that two hours a day. Uh, and, uh, you know, sometimes I might have the best of intentions to exercise, uh, every day. But, uh, we've got it, uh, pretty much marked on their calendar. They are exercising every day and, uh, and don't get to skip very often. And so, uh, uh, and, and when they do skip, it's usually for a space walk, which is pretty, uh, physically, you know, uh, has a lot of physical endurance to it as well. And so exercise is one of those big things that, that really has a, a big impact on the astronauts. The other one is, is probably diet and, and, you know, making sure that they've got the right diet. Uh, and, and, you know, things like vitamin D uh, which are important in bone health, uh, especially if you're not getting direct sunlight, which they're not when they're on the ISS, um, and, uh, making sure that they've got enough calories and enough protein to, uh, keep their muscles, uh, in really good shape as well as their bones. Um, and again, on the psychological side, the astronauts talked about what a big impact food is, and that, uh, one of their favorite things is when the progress comes up and they, uh, the, the Russian progress and they open the hatch and they can smell the fresh fruit. It just wafts through the, the entire module. And that what a psychological impact, uh, that is. And, uh, Scott Kelly mentioned something that I really hadn't thought about once was that, uh, one of the things that he, he missed and he, uh, really enjoyed, uh, was rain. Uh, you know, they don't, they don't get to see smell and or hear rain for six months to a year, depending on how long their mission is. And I think Scott, when he got back, stood in the rain for a little bit just to, you know, re-experience it again. It's little, little things like that that you think of physically, but also, uh, mentally that, uh, impact folks that, you know, that we take for granted every day, walking in a, in a green woods or, uh, feeling rain and, and, uh, you know, hearing the raindrops or smelling that fresh rain when it falls. A lot of those different things, uh, that, um, the astronauts, uh, have mentioned when they get back. And so there's, there's a lot of it that is both physical and mental, uh, you know, to keep the crew healthy. And it's, uh, it's always interesting to get their feedback after a mission Host: That is so interesting. And those are little things that you don't think of here on earth. I mean, sometimes when it's raining, it's an inconvenience for us. And here the astronauts are longing for the day. They can feel rain again. So. Interesting. How long would you say it typically takes an astronaut to adapt to life on orbit? Even something as simple as learning to float instead of walk? J.D. Polk: Yeah, you know, it, it depends on the organ system. Um, one of the first things we see is what's called space adaptation, uh, uh, syndrome that, we used to call it space motion sickness, but it's not really motion based. 'cause we, we figured out that we used to have hardened fighter pilots that were used to doing, you know, barrel rolls would still get nauseated when they got to space. So it really wasn't motion connected. Uh, and when you think about it, when you're, when you and I are just sitting here talking, there's the pressure on the balls of our feet. There's the pressure on our rear end telling us where we are. There's the, our eyes telling us if we're even with the horizon, uh, what's called our semi-circular canals in your ears, that can tell you if you're leaning one side or another. Um, and even those, this a, uh, a small thing in your tendon called the golgi tendon apparatus, that if you are leaning forward or back, you have a stretch on your tendon or a laxity of your tendon, uh, that tells you whether you're leaning back or forward. All in all, there's over a hundred different signals that tell you where you are in time and space at one point in time. But when you launch in space after a, an exciting eight minute ride, then all of a sudden all of those signals are gone. Um, your partner might be upside down, so your eyes are not, uh, uh, a good thing to rely on. You don't have the pressure on the balls of your feet 'cause you're floating. You, you, your limbs are a little bit flexed, so you don't have any stretch on the ing tendon apparatus. So all that fluid in your semi-circular canals is floating. And so all of that in one, you know, in a, in a few seconds when you first get to microgravity and, uh, your brain says, I'm not really sure what just happened, but I think I'm gonna get nauseated or throw up. Um, and that we see that in about 78% of astronauts. Um, and what's interesting is that phenomenon goes down each time they fly. It's, it's like the brain remembers, okay, this is that space flight thing, so I'm not gonna get nauseated this time around. Um, and so first time flyers, uh, very frequently get that space adaptation syndrome. We do have a medication that we use to treat that. Uh, it's a very old medication called Phenergan, uh, that we use. Uh, and that prevents the nausea. And, and even the Phenergan itself behaves differently in space flight. Uh, that drug, uh, is cleared through the liver and, and, uh, because of that fluid shift, it has a faster onset than it does on the ground and a faster offset than it does on the ground. So we can get the astronauts over that hump of that nausea right away. So that's, that's the first thing that, that we see for them to get adapted to. Uh, and then that takes a couple days for them to adapt to that neuro vestibular challenge. Um, and then their heart rate goes up for a little bit for about three to four weeks. Uh, as all that fluid moves, uh, upward into the chest, your, your body actually thinks you've got too much fluid on board. It doesn't realize all that fluid's coming from your legs, and it takes a while for you to downregulate, uh, the blood production as well as, uh, you know, get rid of some of that fluid, uh, coming through the kidneys and other things to equilibrate that fluid again. And then, uh, bone is another one, uh, that takes, uh, weeks to months, uh, where you, you know, you start to have a little bit of bone loss, but hopefully with the resistant exercise and the diet that we're curbing a lot of that. Um, and so it's the different organ systems adapt at different times. Um, the vision things that we've talked about with what's called sands or, uh, space flight associated neuro ocular syndrome, we have really long names for things in space flight. Um, that one, we usually don't see vision changes till about month two or three in an astronaut, um, because it takes that long for the optic nerve to swell a little bit. Um, and so each of these things, uh, it's interesting, they have different milestones and, and occur at different points along the, uh, the continuum in space flight. And I think that's one of the advantages, uh, quite frankly, to long duration space flight. Many of these things we had never seen in short duration. You know, the shuttle missions were 14 days or less, Apollo less than that, uh, you know, mercury, Gemini less than that. So, you know, the long duration, uh, missions in the ISS has a, of allowed us a glimpse into a lot more adaptability of the human organ systems in space, uh, which I think helps us then to figure out what we need to do going on to the moon and Mars. Host: Now, I know astronauts go into quarantine ahead of launch to avoid bringing anything up to the station, but is it still possible to get a common cold on orbit? J.D. Polk: Well, it's, uh, it's never impossible. It always depends on, you got new people coming up on occasion, um, and, uh, usually you're not exposed to a lot of viruses, uh, on, you know, on orbit, uh, unless, uh, somebody's bringing up something. And so that's one of the reasons we're so strict with the quarantine, of course, uh, covid, uh, backed that quarantine up even further a little bit. Um, and we make sure the astronauts are well vaccinated on, on all sorts of things from flu. Uh, but also, uh, you know, uh, varicella or zoster, uh, you know, we can have viral activation on orbit. Uh, and some of it is just reactivation of viruses that you are already harboring in your body. You think about a, a college student who's studying for an exam and they get a cold sore that's actually a reactivation of a virus, uh, that same virus along the same family as chickenpox and things that, that you have, and it can, space flight is stressful, it can reactivate those viruses as well. And that's one of the reasons we do vaccinations for the astronauts. Uh, uh, similar to like, uh, varicella and, and, uh, zoster as a vaccine, something that you would normally not vaccinate somebody till they're like age 60 on, uh, but we might be giving it to an astronaut in their thirties and forties just because of that activation from the stress of space flight. Host: How interesting. You have mentioned some of the medications that they have up on orbit, but what about medical equipment and treatments that are available to the crew aboard the station? J.D. Polk: Yeah, you know, uh, we're fortunate that sometimes we fly a physician, uh, but not always. And so, uh, most of the crew with each mission, we have at least two people that are trained to be what's called a crew medical officer. Uh, and they're think about, uh, an emergency medical technician advanced, uh, that's kind of the level that they're trained to. They know how to defibrillate, they know how to, to put an airway in, they know how to draw blood. Uh, they can be walkthrough the basics of an ultrasound, and we can guide them a little bit more on ultrasound, go a little bit left a little bit, right? Um, and so they've, they've got a lot of those different things that they can do. Um, uh, along that lines of that EMT advance. Now when we have a physician on there, of course, uh, they have, uh, vastly more skill just because of their training, but, uh, uh, the majority of, of the folks on board are trained at that, what we call the CMO level or the, the crew medical officer level. And sometimes we even take them to the emergency department and, uh, have them do procedures there and learn how to do, uh, some of these procedures, including suturing and other things, just so that they'll have the exposure. Um, and, uh, when you have that exposure, then, then it's, it's not as scary when you see it, uh, for the first time on orbit or elsewhere. Um, and, uh, you know, learning how to give each other's, uh, in injections, so like for space adaptation syndrome and things of that nature, uh, so they get quite a bit of training, some of it just in time, some of it recurring. But, uh, most of it in, in about that 16 to 20 hour range of an EMT advanced. Host: Now, we often get questions about mental health on orbit, which we've touched on a little bit, um, especially around the holidays. These questions come in. How do astronauts manage the stress, isolation, and mental health during these long duration missions? J.D. Polk: Yeah, that's a great question. Uh, you know, first we select some folks that are pretty hearty folks, when we go through the selection process. I mean, they are, uh, quintessentially the right stuff. I mean, we, you're not gonna go send, uh, someone who's claustrophobic and a narcissist onto a long duration ISS obviously. Um, but, uh, also, you know, they, they, uh, they have a great deal of mental health to be able to compartmentalize their work and separate that from the mission. Uh, but then they also have what's called the IP phone, uh, or the internet protocol phone, so they can keep in contact with family, uh, which, you know, that I think study after study shows human connection really helps, uh, your mental health, uh, including as you age. And that's something that we see on orbit as well. Having that connectedness to family make, you know, feeling it like you're not, uh, missing events with family, um, connecting, sending emails to folks that have the ability to keep up on news and, and see what's going on on orbit. Uh, but also we do those, uh, those, those private psychological conferences to check on how they're doing. Um, and they have the ability to reach out with that IP phone, uh, when they're not, uh, in the midst of work and on their off time. Um, and, uh, you know, I've, I've gotten a call a couple of times, which, uh, you know, half the time I let my, I don't know about you, Courtney, but I let my phone go to voicemail half the time if I don't recognize the number. Of course. And so there's that one particular number when I, when I see it now, I know I need, I have to answer that one. That one's, that one's a little bit more than a long distance call <laugh>. But, uh, but they do a great job of, uh, staying connected, uh, with family, and it's really important. But it's, it's not only important for the astronaut, but it's important for their family. You think about, uh, you know, somebody growing up that's 8, 9, 10, 11, 12 years old, uh, and their parent is, uh, gone for six months to a year, and, and many of that of them have had military deployments before. Families get used to that. But that, uh, connectedness and the ability to, to, uh, keep those family bonds are important for their mental health. Host: And I know there's an option to call, but you can also video call from orbit, correct? J.D. Polk: Yes, you can. Yep. Absolutely. Host: I assume seeing the faces really helps too. J.D. Polk: It does. And, uh, I don't know if we may touch on this a little bit, but, uh, one of our flight surgeons, uh, Joe Schmidt is working with, uh, the Microsoft HoloLens, which can actually project the individual onto the ISS. So we've, we've, we've got this video, it's, it's, uh, it's kind of, it's interesting that it's also just, you know, amazing to me where it's like a hologram like Star Wars hologram of Joe Schmidt projected onto the ISS. And so, uh, think about being able to project the, you know, your, your child or somebody else onto the ISS to have that conversation, not only face-to-face, but you be able to see them in three dimensions. It's, that's kind of neat. Host: That’s So cool J.D. Polk: and scary simultaneously. Yeah. Host: So I'm sure, obviously the resume is one thing that is heavily looked at before hiring an astronaut, but are there any unique psychological test or training that astronauts undergo before or during their missions? J.D. Polk: Well, I, I won't give away the farm on what exactly we're looking for, but, uh, we have, we invite a host of psychologists and psychiatrists, uh, so that it's a, a large group of folks that are actually, uh, evaluating and looking at the astronauts during the selection. And usually we have group activities where they're, they're doing team activities and, and you can kind of tell with if somebody is team oriented or if somebody is merely out for their own self and, and, uh, you know, uh, not really going to do well on a team. And, and, uh, that's what they're looking for. They're looking for team cohesion. They're looking for somebody that has a, a service before self mentality, uh, and someone that, that is going to, uh, align with that mission, and it's not gonna be all about them. And, uh, and, you know, we're about, uh, furthering the mission of, of the agency and, and, uh, the United States. It's not just about the individual. Um, and so that's one of the biggest things they look for and, and the ability to adapt. And, uh, and they, they all get together and, and they kind of have a scorecard, but, uh, I'm pretty sure they ask the, uh, individuals that are on the team too. Um, and so, uh, you know, if you're on a team of 10 and nine outta 10 people want you voted off the island, you're probably not gonna be an, um, but, uh, you know, there's, as to a specific test or things, I, I won't give that away, but they, they do a battery of different tests, mostly aimed at making sure folks, uh, are adaptable and can work in a team. Host: That's great. Now, I've heard it both ways on sleep. Some astronauts say they sleep the best they've ever slept in space. While I've heard some say that they prefer their own bed at home, how does space impact astronauts sleep pattern? J.D. Polk: Well, the one good news is, uh, you know, gravity causes your tongue to fall back in your throat, and you can snore on the ground. <laugh>, you don't snore in space. Uh, your, your tongue does not fall back in the back of your throat due to gravity. So, uh, you know, uh, we don't have any complaint about, uh, astronaut, uh, you know, John, John over heres snoring and keeping the rest of us awake. It does not happen. So that's, that's one good thing, uh, about space flight. Um, but, uh, you know, you have 17 sunrises and sunsets, so it, it's difficult to get into a circadian rhythm. Um, and that's one of the reasons that it's important that we have, uh, a, a timeline when they get up and they go to bed, and we have certain lighting that occurs with, uh, with an amount, uh, some small amount of blue light and other things that are, that are in that lighting to give them some feeling of daylight, if you will, uh, to help get their cortisol, uh, aligned and, and so that they can sleep. Um, some folks, uh, you know, sleep only six hours normally, and, and they find that they're sleeping only six hours on ISS as well. And, and as you mentioned, some people, uh, you know, sleep like a bug in a rug, and they're, they're, uh, sleeping and feel like it's the best sleep they've ever had. Uh, you don't have to worry about turnover, you know, feeling like you've compressed this arm or that leg too much. You know, sometimes we all do that when we're, uh, lying in bed at night and feel like we've laid it on one side too long, don't really get that on orbit. And so, uh, some people feel like it's the most restful sleep they've ever had. Host: Can you explain the sleeping quarters on the station? How do you prevent an astronaut from floating off in the middle of their sleep? J.D. Polk: Yeah, sometimes it's just as simple as having, uh, what, what amounts to a sleeping bag, if you will, that keeps them, uh, in place, but also we want them to be able hear any cautions for alarms or, you know, if there's a fire alarm or smoke alarm or something else going on. So we have a sleep quarters that allows them, uh, you know, to where they can hear the caution and warnings. Uh, but also, uh, some folks feel like they need, uh, like a compression or a cover or, or some feeling of a cocoon, if you will. And so they can have that as well. And that's, uh, but very often they sleep and their arms float up, uh, and their elbows are bent and, and they're just, you know, floating in front of 'em. And, uh, and that's typically the position that, uh, a lot of them sleep in. Host: How long does it typically take for astronauts to adapt to sleep on orbit? J.D. Polk: You know, I think that really depends on the astronaut. Uh, some folks adapt very quickly. Um, some folks take a while to get into the, the rhythm, uh, and the timeline. And I think probably that also aligns with how often you have flown that when you're a first time flyer and it's new and it's exciting and, and, you know, you're, you're nervous 'cause you don't wanna, uh, you wanna make sure you follow the instructions on the, the procedures that you're doing and et cetera. Um, you know, you probably have some apprehension and it takes you a while to, to, you know, calm down and be ready to, to sleep. Whereas, uh, repeat flyers are like, oh, it's bedtime. And so it, it probably does, uh, change a little bit based on frequency of flight. Host: You mentioned earlier how important nutrition is for astronauts in space. What kind of diets are developed for the astronauts to maintain health? And is it different for each astronaut? J.D. Polk: It's a little bit different, uh, based on what their nutritional needs are. We, we have a good idea of what their bone density is, um, how their muscle, uh, is, what their caloric intake needs to be to maintain their metabolic, uh, reserve. Uh, all of those things are calculated. But also, um, the food lab does a great deal of testing of food, uh, to see what the astronauts will like. Um, and, uh, knowing that, you know, when you have that fluid shift a little bit, your, the palate changes a little bit. You think about your taste buds have sour and sweet and, and, uh, you know, now you're getting a little bit more blood flow to certain parts of your tongue. Um, and so folks, uh, tend to tend to crave a little bit more spicy foods on orbit. Um, and, but they have the ability to test taste and, and test a lot of the foods in the food lab, uh, on the ground to get an idea of what they want. Uh, but also we, uh, of course augment that with things, knowing how many calories they need, how much protein, um, you know, how many, uh, good fats, uh, soluble fats, um, vitamin D, um, all of those things, uh, that, uh, our food research team, uh, keeps track of. And, and the, the nutritionists build a, a big lab, uh, if you will, or library of, of different food items that they can, uh, take. Uh, and of course, there's things that we want from a psychological reason, you know, that, uh, some folks are like, Hey, I really want that ballpark mustard that I had when I was, you know, a kid. Well, okay, yeah, we'll, we'll fly that and, uh, and see if we can do things that, uh, help them on the psychological front as well. Host: Yep, that makes total sense. I just, like you mentioned earlier, I have also heard how exciting it is for them to get those cargo resupply missions and open the hatch and get to see and smell some of that food coming in. It's so exciting. Earlier you mentioned the elephant in the room, which was radiation exposure. How is radiation exposure monitored and mitigated for astronauts in space? J.D. Polk: Yeah, we have a, a radiation monitoring device, but we also have different instruments that monitor radiation on the ISS. And typically we have, we just updated our standard on radiation to 600 millisieverts, uh, across the board for astronauts. We, in the past, we had had a little bit of a dichotomy between male and female, uh, based on some studies that came about from Hiroshima and, and others that, that showed that females were a little bit more at risk for lung cancer. Uh, you would think, you know, most of us would assume breast and ovary, but, but lung cancer may not be one that, uh, would rise to our, our thoughts right away. Um, and so, uh, it used to be that that female astronauts, uh, had a slightly shorter, uh, standard or shorter career from a radiation standpoint than male astronauts because of that, that cancer risk. Um, but we've looked at that from a mean standpoint, uh, looking at clinical means and longevity and, and, and what our own cancer, uh, results have shown. And also looking at larger studies from the Department of Energy, um, and, and really just amassed a ton of different data together and then worked with the National Academy of Medicine to, uh, figure out what should be the next standard. And that when we updated it, uh, it was updated to 600 millisieverts for males and females. Um, and so, you know, that you can, uh, you can fly multiple, multiple missions, uh, before you reach that. Uh, the, the difficulty that you have with, uh, like exploration missions is, um, looking at your exposure, we'll probably bust that 600 millisieverts going to Mars and, uh, and back, for example. Um, and so you look at all the different risk factors that the astronauts, you know, there's some informed consent they need to know what they're getting into. Uh, but we as the government also then monitor the astronauts for their lifetime, whereas, you know, a corporate entity might not have to do that. They, they can have you sign a waiver and we, we can't have you waive your rights, if you will, uh, and the federal government, and, uh, we monitor the astronauts throughout their entire lifetime. Um, and so we see them back at the Johnson Space Center Clinic, uh, healthcare clinic to, uh, to look at things like cancer risk for astronauts as well, just to make sure we're monitoring them. Host: So the number that you mentioned, could that be a certain amount of days or does each body react differently and the days could be different for the same amount of exposure for two different people? J.D. Polk: Yeah, a lot of things going to it, it could be days, but it could be exposure. Um, hydrogen, for example, is a good blocker of solar radiation. And so, uh, you know, if somebody was doing more spacewalk and is exposed outside the, you know, and as we go through the, uh, south Atlantic anomaly and through the poles, uh, versus somebody who wasn't doing any space walks, um, or if your mission happened to be closer to Solar Max versus Solar Min, there's a lot of different variables that can, uh, come into play. And so, um, you know, the same person can do a six month mission, uh, and you two people might do a six month mission, and they have slightly different doses that they, uh, acquired, uh, from an exposure standpoint. And a lot of that has to do with, um, you know, how the active the sun is at that time. Um, and the other thing that that does come into play is the age of the astronaut, too. Um, you know, if, if I'm exposed to a particular amount of radiation and let's say I'm gonna get, there's a risk that I could get cancer in 30 years, well, if I'm 27, that could be pretty serious. You know, I'm getting it at 30, at 57, and then, you know, that could, uh, impact the next 30 years of my life. If I'm a 57-year-old astronaut and I fly and it's gonna be, you know, 30 years later, well, the likelihood that I'm probably gonna, you know, leave the planet for a different reason, coronary disease, old age, et cetera, uh, is there. And so, uh, uh, Bob Cabana used to remind me that, uh, you know, radiation, uh, is less of an issue the older you get, so he was insisting that he could go to Mars when he's, uh, yeah, after he retires. So I, I I, I told Bob I'd, I'd vote for him for sure. Host: I love that. You've told us a lot about the different kinds of effects the astronauts feel while on orbit and how your teams on the ground monitor those effects in real time. Are there any changes made to mitigation plans based on what those different markers may show? You mentioned that the blood draw analysis and food and water tracking exercise. Would there ever be a situation where you're tracking something and you need to make changes? J.D. Polk: Yeah, absolutely. Uh, in fact, we have what are called acers, which are astronaut Strength and Conditioning Rehabilitation Specialists. Um, and they look at the exercise regimen of the astronauts, and they are, um, also developing exercise regimen based on their bone density and their muscle strength. And so we may see or make changes to that. For example, uh, they, one astronaut might need a more rigorous exercise program or more loading, uh, through the hips, uh, and back, uh, for their resistant exercise as opposed to another astronaut. Uh, one astronaut might need, uh, uh, pharmacologic help with, uh, what we call, uh, bisphosphonates, uh, to keep their bone density, uh, whereas another astronaut would not, uh, or another astronaut might need an increased vitamin D uh, load versus another one. So yeah, there are different things that we change, uh, based on either what we're seeing pre-flight or what we see in flight, uh, to maintain the optimal health of the astronauts. Host: So now, we've talked a lot about crew health on orbit, and I wanna move into the recovery and rehabilitation once those astronauts return to earth. So what is that rehabilitation process like for astronauts when they return from space and when does it begin? J.D. Polk: Yeah, it begins almost immediately. They, you know, when they first return, uh, they are low on what we call preload. As we talked about before, you have all this fluid moving up into the head and thorax, but, and your body perceives that you've got a fluid overload. And so you, you decrease the amount of blood that you are actually producing in your bones and, and with what's called erythropoietin. Um, and also, you know, decrease some of that pre, uh, free fluid or plasma volume. So they're about a liter or two behind, uh, when they first land. That's why if you've, when you see them land on the Soyuz, uh, you know, they're on the, on those cots that are reclined, it's because if we had them stand up, they probably get lightheaded and uh, and pass out. And a lot of that is because their lower extremities are not used to squeezing those vessels to push that blood back up to their heart. J.D. Polk: But also, uh, their tank is a little low, if you will, uh, the fluid, they haven't needed that much fluid or plasma volume before. Um, and so one of the first things we do is, is give them hydration. Uh, and that might be as simple as Gatorade. Uh, you know, that may be, uh, we do a salt load, uh, before they, uh, uh, before they come home and do a fluid loading before they come home. But we give them more fluids if they're able to, to, uh, take fluids when they get back. Uh, we could do IVs if they're nauseated, and I feel like they can't take oral fluid. Um, and so a lot of that starts right away. And then it's, uh, a lot of it is what we call biofeedback or retraining the brain. Uh, they'll, they'll have a very wide base gait. They'll walk like, uh, John Wayne going into the saloon in a Western movie initially, because they, they have that unstable gait. They, that neuro vestibular wise, they, they feel like they, they are unsteady. Um, and it takes a little while for the brain to readapt to, uh, get that, you know, all those different signals, uh, as to where they are in time and space, like we talked about with your semi-circular canals and your vision, uh, back in synchrony. Uh, and that usually takes a, um, you know, sometimes in some astronauts it comes very quickly within several days. Others, it takes weeks for that to occur. Um, there's a lot of variability there. We, we, there's not really a good second guessing which one's going to have what, you know, we've, we've some seen some astronauts that have taken a couple of weeks that, um, and then even on their next flight took a couple of weeks as well. J.D. Polk: And so it did, uh, that's one of the reasons we don't allow them to drive or fly, typically for, uh, almost a month, uh, uh, after they get back, until they get all that nerve vestibular, uh, system, uh, working again and in good shape and, and buffered. Um, if you think about it, that, that feeling, I'm sure you've had it before Courtney, where you, you're about to fall asleep and then you feel like you're gonna fall out of bed and you, you have that little jerk response. Yes, they get that as well. They, it's that feeling like they're, they're gonna fall or they're gonna move, et cetera. Um, Tom Marshburn told me too, that, which I thought was pretty funny, that for six months he would take a drink and he'd put the glass out there and the glass would stay right in front of him. J.D. Polk: Um, and he had gotten home, uh, into his kitchen, and he took a drink and put the glass out there, and the glass, you know, of course fell to his feet, and you, it, it's just readapting to some of those things that they've been used to for six months, takes a while. Um, but, uh, usually by the 30 day mark, they're doing pretty well. Bone is probably one of those things that takes the longest, uh, um, for, you know, a one year mission. It might take all the way up to three years to re yeah, adapt all of that bone and get the, all of that density together. But the, the interesting thing about bone is that although you may lose the bone in the matrix, it comes back as cortical bone. And so you think about chalk, chalk is dense, but it's not very strong. And so we, we want that bone to readapt and, and have the matrix solid, uh, not necessarily for it to come back just solely on the cortex or the outside of the bone. Uh, so it does take a while, uh, bone probably the, the longer for those things, uh, to adapt. The, the, probably the more shocking thing for us was this eye, uh, issue with sans and the optic nerve. We, we thought that once they got back to gravity, that that, that would subside very quickly. Um, and, uh, and several astronauts, we saw that that pressure, uh, on spinal tap was, was still high for quite a long time. And it, and it took a long time for their vision, uh, to, uh, get, uh, close to, to normal again. And so, um, that just tells us that, you know, we're really good at pumping blood into your brain to make sure that you stay alive. But, uh, there's not a lot of mechanisms to pump pump fluid outta your brain. You, you don't exactly have a sump pump, uh, up hidden up there. And so it, it takes a long time for the, the venous flow in the lymphatics to get rid of a lot of that, that swelling. Host: Is there a standard timeframe on NASA's end for when the rehab process would end for an astronaut? Or is it different with each person? J.D. Polk: Yeah, it's different with each person, uh, based on, on where they're at with their exercise, with their neuro vestibular, um, you know, certainly we let them, you know, they, they go home very quickly and, and we allow 'em to go home very quickly. Uh, but, uh, you know, getting back to driving, typically we have that as a policy at a 30 day mark. Some people are probably better before that. Some people, you know, take right up to that. But we found that typically 30 days was when most people were, were good to get back in, in the aircraft or were driving again. Um, and so we, we try to have a little bit of a safety buffer on the backside to, to, uh, ensure that they are, are safe, but also that they're, they're, uh, on the right, uh, trajectory from a physiologic standpoint that they're recovering well. Host: So knowing what we know now, after years of research, does space travel accelerate the biological processes like aging, for instance? J.D. Polk: Yeah, you know, to some degree, I, you could probably say that certainly from a, from bone loss standpoint, uh, you know, when you think about osteoporosis, yes. Um, but, uh, we're getting better and better at mitigating some of those either with bisphosphonates, resistive exercise, vitamin D, all of those things that we do. Um, but it's not perfect yet. Uh, and so yeah, to some degree, but if you think about the stress of space flight reactivation of viruses, uh, muscle loss, bone loss, those things very much mimic aging, uh, to some degree. And even radiation, uh, and its impact on cells, uh, mimic, uh, radiation or, uh, aging rather. So it's, uh, you know, to some degree, yes, it's a, it's a pretty good, uh, parallel between those two. Host: I think sometimes people do not make the connection between the benefits for humanity and the International Space Station. I think one of the best things about the International Space Station is the benefits for life here on earth. What insights has astronauts health research provided for improving healthcare here on earth? J.D. Polk: Oh, wow. This, that could be a three day conversation, but we'll, we'll start with a couple that I think are really fascinating. Uh, one, we can make different proteins and different crystals on orbit, uh, than we can on the ground. Um, and that has been helpful, uh, and including in the pharmaceutical industry. Uh, one of the drugs that, uh, is used for type four cancer, uh, especially type four lung cancer, a grade four lung cancer, uh, is called Keytruda, and it has some of its, uh, work done on the International Space Station. Um, and, uh, red wire recently in the last year did an experiment where they actually 3D printed a human knee meniscus using, uh, you know, human stem cells, uh, as the, uh, the bioproduction, uh, you know, substrate and made a human knee meniscus on orbit. Now, you would think, okay, what, why? That sounds pretty cool, but why make a human knee meniscus on orbit? Um, well, gravity has a tendency to call, cause what's called cell senescence, where the cells kind of collapse or smash each other, but due to the weight of gravity. And so you can make a matrix if you can, uh, on orbit and microgravity that, uh, much more easily than you can on the ground. Um, and, uh, they also 3D printed, uh, beating cardiac cells, uh, recently. Um, and that, that has some profound implications. Uh, the, the bioprinting, especially if you think about right now on the ground, there's probably a, you know, some family unfortunately has a 10-year-old who's waiting for an organ, uh, a liver or a kidney, uh, or even a heart. And you have to, unfortunately, in the United States right now, the way that this works is you have to wait for some other family to befall a tragedy, uh, somebody, uh, to donate their organs, uh, somebody to have a motorcycle accident or some other thing before an organ's available. J.D. Polk: But if you think about being able to take stem cells from someone, spin them culture, those stem cells, and then 3D print, uh, an organ or a matrix, imagine being able to 3D print, uh, a kidney that is made from the child's own stem cells. They're no longer on rejection medications for the rest of their life with the risk of infection and all of those things. It has some profound implications, and we're, we're just starting on that area and, and doing some really cool science on the International Space Station right now and in microgravity. I think that's also the, uh, probably, uh, one of the biggest reasons to continue microgravity research, like for the, uh, commercial, uh, lower, lower orbit development program, um, to continue and, and continue that research, especially on the commercial side, uh, to keep pushing those boundaries. Um, even Moon to Mars, uh, you know, one of the things we've been looking at is, uh, 3D printing of medications. Um, I can't take the entire CVS or Walgreens pharmacy with me, uh, you know, to, to Mars. Yeah, we would like to take food and water and other things. If I took the whole pharmacy, you wouldn't have room for anything else. Um, and so looking at can you, can you 3D print medications, if I took the constituent chemicals, um, and you knew what the recipe was to make a Zithromax or a Cipro, uh, to be able to 3D print those in a just in time manner. And if you think about the profound implications that would have, uh, on the ground to either hospitals or third world countries or other places, uh, to be able to three, 3D print, uh, medications on demand, if they know the recipe and they have the, uh, constituent chemicals there. Um, so there's a lot of things that we're doing that, uh, really are, are pushing the boundaries, uh, on healthcare that will have a, a profound impact to the ground. That the only difference, Courtney, is they, we don't really have a sticker that says, you know, made at NASA or done at NASA. We don't slap something on there. Um, even the smoke alarm in my house came from Skylab by technology, but it doesn't have a little blue NASA meatball on it. So there's so many things that we develop or, or, uh, push the boundaries on that, uh, eventually get taken off in, in the commercial sector. But, uh, many people don't know that they had, uh, at least part of their origins in the space program. Host: That's absolutely incredible. And it's a great segue to my next question. How do you think these advancements that we're making now in medical technology will improve the safety and health of astronauts when we go even deeper into space? J.D. Polk: Wow, that's a, that's a great question. You know, I, I think there's two things. Um, one, uh, the commercial sector and having so many different partners, not just government partners, but commercial partners now, et cetera, uh, when you get more and more people involved, uh, in space, they, they start to think outside the box and think of things the way, you know, you might not have done it that way. Uh, and, uh, you start to see innovation, uh, and different sectors and, and in, uh, different ways of doing engineering, different ways of, uh, doing, uh, medical surveillance. All of those things start to occur. Um, and I think that's, that's one of the lasting impacts with this really growth of, of the space sector that we're seeing is, uh, uh, a lot of different companies, uh, being innovative and doing things in different ways. Uh, and that can have impacts not only in engineering, but also in, in medical and, and healthcare as well. And, uh, uh, it's been, and really great for us to see and to work with all of our different partners. And, uh, as we've worked, we've worked with multiple different countries now, uh, as well. And it's interesting to see, you know, how they look at things and how they, what are they developing and what are they looking at or trying to push the boundaries with? Um, and it's, uh, you know, we, we, uh, we try not to be siloed. It's very hard, uh, when you're a government agency to not be siloed sometimes in certain areas, but, uh, just a lot of the crosstalk that we've had with so many different folks, um, it's, it's amazing for me to at least see all the, uh, innovation that's occurring as part of this exploration and the commercial development. But, uh, one of the things that we've done probably recently in the last five years is we've placed all of our standards, um, on our website and, uh, in fact, it used to be a highly guarded secret, uh, for what was the, uh, standards to get in to become an astronaut when you applied. Uh, and we, we, you know, you could probably get the missile codes faster than you could have gotten my, uh, my medical standards for how to become an astronaut. Um, but we've, we've reversed that and we've placed that on, on the website now, so anybody can pull that up and they can see our, our standards for developing a spacecraft and our healthcare standards. And, and mostly that is because we want everyone going to space to be safe. And, uh, you know, all boats float with a rising tide. And we, uh, we want everyone to see what our lessons learned and, and, and what we've, uh, developed and over 65 years of human space flight. Um, but we're learning from them as well as folks read our standards or, or look at them. Uh, we'll get emails on occasion saying, Hey, have you guys thought about this? Or, Hey, we're looking at this, at this university and we found this. Could, you know, you might want to think about this. Um, and it's, uh, that that kind of innovation around the globe is really, it's made for an interesting partnership as we go, uh, to the moon and Mars. I think it's gonna be instead of one government of, you know, you're going as a planet with a collective public private partnership in multiple countries. Host: Okay. I'm really excited for this question. When you look back to when you started at NASA and where we are now, what are some of the most remarkable advancements in discoveries you've been a part of that you're most proud of? J.D. Polk: Oh, wow. Um, you know, there, there are things that, um, you don't realize that space flight can have an impact on. And I, uh, you know, I was fortunate to be part of the team that went down to help rescue the Chilean miners, uh, over a decade ago. And, uh, I remember when that phone call first came in and, uh, you know, the Chilean ambassador, uh, was in DC and had, and had talked to Charlie and said, Hey, you know, you guys keep people alive and an enclosed environment. Uh, can you help us keep these miners alive until we can get them rescued? And, uh, I remember that call coming down from headquarters down to JSC and, and, uh, us four of us getting into a, a room together and starting to whiteboard this and thinking, actually, you know what? We probably can help on this. We actually have lessons from space flight on how to keep somebody alive in an enclosed environment and what to look at and, and, uh, how to do these things. And even the engineering on, on, uh, yeah, helped a little bit with the engineering on the, uh, the, uh, module that would bring them up through the, uh, uh, through the tunnel. Um, and you know, if you had asked me three weeks before that, uh, if space flight had anything to do with, uh, mine rescue, I probably would've laughed. Uh, and then, yeah, there we were. And then, uh, you know, 31 days later, uh, pulling out, uh, you know, healthy miners, uh, and, uh, and everybody coming out alive and so that, things like that where you, you where it's right in your face, that space flight does help, uh, contribute to things on the ground. And, um, and looking at all the different science that the 3D printing of organs and, and, uh, 3D printing of medications, all of these things that are going on right now, I feel like I'm really right on the bow wave of a lot of, uh, innovation and change that is occurring due to space flight. Host: Wow, that's incredible. Dr. Polk, thank you for all of your work that is not only supporting our astronauts on the ground and in space, but for your work that is impacting life here on earth. And of course, thanks for coming on the podcast today. J.D. Polk: Uh, Courtney, thank you. And thank you for all the work you do. Uh, I'm sure somebody's gonna buff this and make me sound a lot better at the end, so, uh, appreciate all the work you guys do and, uh, and PAO and public affairs and, uh, uh, appreciate all the time and effort, uh, today as well. Host: Thanks for sticking around. I hope you learned something new today. Our full collection of episodes is on NASA.gov/podcast. You can also find the many other wonderful podcasts we have across the agency. On social media we're on the NASA Johnson Space Center, pages of Facebook, X and Instagram. Use the hashtag #askNASA on your favorite platform to submit your idea or ask a question, just make sure to mention it's for Houston We have a podcast. This interview was recorded on January 6th, 2025. Thanks to Dane Turner, Will Flato, Daniel Tohill and Dominique Crespo. And of course, thanks again to Dr. Polk for taking the time to come on the show. Give us a rating in feedback on whatever platform you're listening to us on. And tell us what you think of our podcast. We'll be back next week.
Most NASA images are in the public domain and free to use. Credit NASA as the source. Check NASA's media usage guidelines for details. Images featuring identifiable individuals may require additional permissions.
NASA ID
Ep370_Spaceflight_Adaptation
Date Created
January 31, 2025
Center
JSC
Media Type
audio
Download this audio in multiple resolutions. All NASA media are free for public use.
Audio
Full
