Lessons Learned from Life in Space

They’re among the most studied individuals on the planet, so unique in their circumstances that an exclusive branch of medicine has been devoted to them, indeed a new subcategory of physiology itself. Their experiences teach us about the fine delineations of human biology – as well as its inherent vulnerability. I’m talking about astronauts, whose explorations on behalf of humanity take them far beyond the landscape of earth and the natural conditions of human life. We read about their pioneering endeavors. We see the spectacular images, possible because of their labors. Yet, we know little of their experiences and the physical struggles they endure in the name of discovery.

To us, they might seem the epitome of vitality and enthusiasm as they wave their greetings from space or upon return from their voyages. Truly, these men and women must love what they do. They must value the extraordinary work of space travel – both its inquisitive human quest and the resulting technological possibility. They bring more than heart and soul to their endeavors after all. Their bodies bear the brunt of profound adaptation few of us can envision, harsh acclimatization unimagined until a few decades ago in human history. Truth be told, we’re only beginning to understand the multifaceted adjustment space travel induces – the short term challenges and sometimes permanent emblems of living beyond the bounds of human habitation.

Upon leaving earth and entering what’s known as microgravity, the body processes the cues of its new environment and the physical demands within it. Without substantial gravitational pull, fluids shift toward a concentration in the upper body, and in the early days of a mission diminish by almost a quarter of total volume. Blood flow slows as does the distribution of nutrients. It becomes more difficult for the body to regulate blood pressure and maintain a consistent heart rate. The heart muscle slowly weakens in the face of lesser demand.

Without the anchoring effects of gravity, a sense of balance is difficult to achieve. At least half of astronauts experience a period of spatial disorientation, nausea, and headache in what’s known as Space Adaptation Syndrome. As circadian rhythms are thrown off, sleep becomes difficult and subject to frequent disruption. The immune system becomes depressed, although scientists are still searching for the exact cause. Research shows that in a zero-gravity situation, the body doesn’t turn on the majority of genes related to T-cell activation. (The only other physical condition with this significant an impact on T-cell process is HIV infection.)

In a feat of efficient adaptability, muscle and bone deftly respond to the decreased demands of the physical environment. Without the weight-bearing exertion induced by gravity, the body’s muscles devote fewer resources to producing muscle-building proteins. Experts have measured the loss at approximately 2% per week. Higher cortisol levels measured during space travel also likely contribute to breakdown of muscle.

The orchestration of bone formation and break down also shifts in response to the lower physical demand. Bone producing osteoblasts curtail their activity while the natural break down and recycling activities of osteoclasts ramp up. Measurements vary from individual to individual, mission to mission; however, bone density loss has been calculated between .6-5% per month. Astronauts who live on the International Space Station for six months showed losses of up to 30% of their bone density.

In an attempt to ameliorate the dramatic impact of space travel on human strength and well-being, experts around the globe have designed an evolving series of interventions. In response to the immunosuppressive effects of space travel, astronauts go through a partial pre-flight quarantine lasting 7-10 days. During the mission, they exercise 2 ½ hours a day 6 days a week on a stationary bike, a treadmill (strapped to the machine), and the specially designed ARED (Advanced Resistive Exercise Device) that creates load in the microgravity environment using vacuum cylinders.

Because their workouts, however carefully crafted, don’t offer the same protective benefit to bones as it does to muscle, researchers and space physiology experts have recently experimented with the use of vibration plates as a supplement to astronauts’ fitness regimen. Some NASA scientists suggest that in addition to vigorous, high load exercise, the “low magnitude, high frequency” stress we put on our musculoskeletal structures just in positioning activities like standing or sitting put growth-stimulating demands on our bones. The vibration plates subject the individual to the high frequency signal that mimics these gravity-related positioning demands.

Upon return from space, astronauts participate in 4-12 weeks of rehabilitation to counteract the muscle and bone loss experienced during their mission.

Although the general processes of bone production and break down resume upon return to earth (to a certain extent reclaiming most losses over several years) the thinning of trabecular bone (found in the vertebrae and around the meeting points of bone in joints and sockets) may not recover. Because trabecular bone is built upon an intricate lattice-like structure, damage to the fundamental structure undermines the overall strength of the bone and leaves the person more susceptible to fractures in his/her lifetime.

What can we learn from these brave individuals who knowingly choose to be thrust into an environment that will wreak havoc with their most essential functioning?

That our own plight, in a sense, isn’t so different.

While the astronauts orbit above us, most of us earthbound creatures exist – either by choice or circumstance (unwittingly or otherwise) – in conditions nearly as alien. We also live as fish out of water, physiologically disoriented and separated from the conditions we need to thrive. And when we peek into the life of a space voyager we see our own, as we too attempt to mimic ideal environmental conditions and give our bodies what they need to prosper. While we don’t have to contest with microgravity, air pressure and oxygen abundance, we’re faced with our own set of challenges (see food, fitness, stress, sun exposure, etc.). For without just the right conditions, profound, and in some cases irreversible, damage follows closely behind.

This world and all of its characteristics – was the cradle for our unique and elaborate development. Although modern life distances us from many of our most fundamental, primal conditions for flourishing, the roots of human vitality remain the same as many millennia ago. Our humanity offers us astounding cognitive and imaginative ability. Yet, the blueprint for our physical progress, our basic health and well-being – in which the grander dimensions of our humanity is fostered – is embedded still in our most primal patterns. (If you don’t know what these patterns are yet, you have some reading to do!)

What say you readers? What other morals are there to this story? Thank you for reading!

About the Author

Mark Sisson is the founder of Mark’s Daily Apple, godfather to the Primal food and lifestyle movement, and the New York Times bestselling author of The Keto Reset Diet. His latest book is Keto for Life, where he discusses how he combines the keto diet with a Primal lifestyle for optimal health and longevity. Mark is the author of numerous other books as well, including The Primal Blueprint, which was credited with turbocharging the growth of the primal/paleo movement back in 2009. After spending three decades researching and educating folks on why food is the key component to achieving and maintaining optimal wellness, Mark launched Primal Kitchen, a real-food company that creates Primal/paleo, keto, and Whole30-friendly kitchen staples.

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77 thoughts on “Lessons Learned from Life in Space”

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  1. Today at the grocery store, I bought a parsnip. The fat girl at checkout had to ask me what kind of vegetable it was.

    1. I’m sure if she was thin, she would have been able to identify it on the spot (is there an eyeroll sign on here?)

        1. This fat girl can ID a parsnip. As a matter of fact, lots of fat people are intimately familiar with vegetables from their long struggles as vegetarians or quasi-vegetarians, leading to insulin resistance and despair.

        2. Thanks for the 9_9 heads up. And I’m really glad to see I wasn’t the only one who was annoyed by that comment. Louise D nailed a very valid point too.

        3. for rolling eyes, WTF, i use


          yes, very insensitive also irrelevant to this article.


    2. What a great comment! Now let’s pick on people with blue eyes. I’m sorry but it is annoying to read a real informative piece and then read your comment. Please keep those types of comments to yourself. The world has enough negativity.

      1. Uh…. “let’s pick on people with blue eyes”?? That’s like saying “let’s pick on people with superior genes”. Bad analogy there Gorm.

        1. Too true. And when you combine blue eyes with green eyes to get ocean eyes you go even farther up the food chain.

    3. Wow Brandon, I’m sure you are slim and handsome and perfect in every sense! How dare a fat girl ask you a question?

      Rude and insensitive ….you don’t know this person’s story.

    4. I am very disappointed to see your necessity in describing the checkout girl by her size as if that is the ONLY reason that she would not be familiar with parsnips. Your reference to her size is both arrogant on your part and offensive. If you cannot speak about a person without using some sort of slam against their deficiencies then maybe you need to take a closer look at yourself.

    1. Hi! NASA is not officially or unofficially implementing either into the existing regimen. But Robb and Erwan were asked to give a lecture to some of the folks from the space med/bioastronautics division. 🙂

  2. I love how you took the idea of those in space, being distanced from the natural cradle of earth, and made an analogy to our modern society being distanced from our primal selves. Thats some literary gold mark!

    Definitely a slap in the face.

    1. I agree. It’s nice to see a piece once in a while that makes one think in an abstract sense, instead of always getting down to the concrete facts and statistics.

      Maybe an idea for an expansion on this article is the possible negative effects of the acquisition of too much knowledge? We obviously know more about the universe, about science and everything in general than our ancient selves, but does this have a negative side? Are most of the facts that we have things we shouldn’t know about and be left to dream and ponder about?

      1. “Are most of the facts that we have things we shouldn’t know about and be left to dream and ponder about?”

        On the contary, the question is why aren’t we seeking out those facts with a much greater hunger as it is knowledge, not reclusion, which has truly set us free to dream and ponder.

        Because of our facts, we now dream of mutiple unvirses, of the warping of and traveling through time and space, of the birth and death of billions upon billions of stars and galaxies, and of a universe begun in a single point of pure light. We imagine invisible matter, nothingness creating enormous amounts of dark energy, additional dimesions that we cannot even access, invisible force feilds of energy surrounding us, and impossibly tiny particles living by rules so extrodinaryly freaky that we cannot understand them outside the language of mathamatics.

        Through our curiosity, we now ponder the completely alien worlds, some filled with fantastic creatures beyond anything we could previously conjure, now perserved in the rocks under our feet, in the stars above us, and existing in lands we never bothered to explore before. We have visions of entire continents colliding and being ripped apart, of incredible machines built from fusions of billions upon billions of bacteria, of a abiding kinship with every single creature on this planet, and of an enduring history of trials for survival measured not in centuries, but in millions of years.

        It used to be that our dreams and musings were extremely narrow visions of worlds based only upon human expectations. We based our earlier contemplations just as much on “facts” then as now; the only difference is that our “knowledge” was derived purely from our everyday experiances and thus our musings were limited exclusively to replicating a human-like world in the mind as well. It is only because of our facts and knowledge that the human imagination has truly been unleashed from its self-centered bounds to explore awesome depths completely untouched by all preceding generations.

        1. Sure, but that doesn’t really answer my question. All of these things that we are now able to imagine, i.e., dark matter, other universes, etc, are all things unrelated directly to human experience, and, in an abstract sense, or not all that different to what ancient man would have thought of anyways: interactions between various layers of the universe, the unknown matter of stars in the sky, etc. If anything, knowing the technicalities and facts of all these things causes more nightmares than good dreams. But what’s the point? I’d rather spend my time thinking about things directly related to our experience.

      2. Woah!

        I had a discussion, briefly about this.

        We simplified it into this understanding.

        1. There is a time to stay in the present moment. In the present moment there are fewer thoughts moving through our heads. Only here and now. Only action, doing, or not doing. No thinking

        2. Similarly, there is a time and place to plan, think, and analyze, so that the next moment we are fully present in, is more efficient, intelligent, healthier, with longevity.

        That’s all I can say for now.

    2. Eh. I am not so into the analogy.

      That said, I took a class from the leading osteoporosis researcher in the country. He has literally consulted for NASA regarding space and bone. Very cool guy and very cool class.

  3. oh jeeeze – that was a “writer’s ” post – nicely done mark –

    regarding the bravery of our astronauts – i think the most emotionally devestating moment in my younger life was watching that bizzare trail of plumes cutting across the bright, cloudless florida sky from the exploded Challenger – still sad about that one…

  4. Well, now we know why they needed so many clones in that movie Moon.

  5. i’ve always considered space exploration the biggest waste of money and intelligence the world has ever seen.

    1. You do realize that the engineering and connectivity required to connect Apollo with Houston paved the path for the creation of the internet, correct? There’s no telling what will be discovered/engineered next as a result of exploring the unknown.

      1. You realize that if engineers had put their effort into genetic engineering instead of Apollo we would have Dragons? I’d rather have a dragon at the circus, than read about the moon mission in history books. (The last moon mission was in 1972 – long before I was born – therefore it is all ancient history to me)

        In economics this is called opportunity cost. Please quit using it as an example – you need to account for the unknowable things we lost before you can claim it was good.

    2. I’ve always considered it one of the coolest things humanity has ever attempted. Isn’t it great how different we all are?

      1. I also admire your positivity. I think space exploration is cool too, yet I am terrified of space!

    3. I’m with Stephen Hawking on this one. Don’t keep all your eggs in one basket. How intelligent would we be if we decided not to *waste* our money and precious intelligence on colonizing of space and then a big asteroid impacts our planet, and we have nowhere to go?

    4. methink the Food Pyramid all the related subsidy of grains & corn is much bigger waste of $ & health.

      look @ how it been killing us & the next generations.


  6. These effects on the human body show how difficult it would be to colonize space. The most likely “planets” humans could live on are the Moon and Mars. However, their weaker gravities would create the same effects as zero-G, only over a longer period of time. It would take some mighty heroic gentic engineering to allow people to live healthy in such places. I can’t imagine a viable society growing on either one.

    Of course, building space stations like an O’Neill Cylinder or a Stanford Torus with near-Earth asteroids, would make colonization much more possible. You could have normal gravity, enough shielding to reduce radiation levels to very low, and as much energy from the sun as you would like.

    I’ll leave the engineering and economics of such structures to others. But it would probably be best to leave most of the exploring of space to the robots.

    1. Some food for thought: If we were actually living in space, then would we necessarily need the same bone density and muscle size? Since we would no longer be returning to an Earth-magnitude gravity, our new body type might suit us just fine? We could probably all squat 1000 Earth pounds on Mars!

      This makes me also think of the battle our bodies are undergoing trying to adapt to the new foods and lifestyles we have today. Adaptation is a necessity for survival in our world. By not doing exactly what our genes and bodies were designed for, we are forcing ourselves to adapt.

      I guess what I’m trying to say is, the 90/10 or 80/20 rule should be part of being primal because it forces us to adapt to our environment, which is what we animals have always done.

      1. You wouldn’t need the same things as on Earth, true, but as Mark said, there are negative health effects, especially that of the heart weakening – and that’s just ONE example. Humans wouldn’t live as long in such an extreme environment, and in order to adapt quickly enough with as few lost lives as possible, there would need to be some genetic engineering involved.

    2. Good points, but we don’t actually KNOW that any of that is true or necessary because we don’t know what will be discovered or created that turns our world on it’s head. Just think: 75 years ago (one human lifetime) no one took a flight to cross the ocean, there were no cell phones/tvs/computers/internet/fax machines/gps/talking movies/escalators/dishwashers/microwave ovens, etc. The way that we live now would have been unimaginable to those living in 1935-LITERALLY. The super exciting thing about exploration is that we don’t know what we don’t know! Grok on y’all!

  7. Recently, I read a book called “The Home Planet,” which had photos taken from space along with comments from various astronauts.

    Upon viewing our planet from their vantage point, all were struck by how fragile is our existence with our thin atmosphere and by the beauty of the earth.

    Upon arrival back home, with the experience of the inky blackness and incredible silence of outer space, they had a renewed appreciation for the colors, smells and sounds of nature.

    Many have dedicated themselves to educating people to appreciate and take care of the only home we have.

    Their bodies may have taken a serious hit but their perspective on our relationship to earth took an expansive and positive turn.

  8. Great post! Too bad that any future trips to space will have to be through Russia. Low Earth Orbit doesn’t count on some commercial “flight to space”! I would be interested in seeing more of that kind of science.

  9. I learned that the makers of the movie “WALL-E” were not so far off in their interpretation of what space travel would do to the human body! Space Blobs! LOL!

  10. Mark,

    It might be my imagination, but I think you’re becoming a better writer even in the year or so I’ve been following. This was well done! I imagine going through the process of writing and publishing a book had a lot to do with that?

    Would you have suspected in the 60’s that writing would be such a passion for you?

    I’m actually starting a new job in private space propulsion in two weeks, so perhaps this has skewed my view in the direction of positive 😉

    1. Also, don’t discount the fact that anyone who’s done a couple orbits is guaranteed to be rich and employable for the rest of their life if they’re inclined. Not to say the discovery and awe aren’t the primary motivators, but even though I have zero desire to be launched myself, one could look at it like a roll of the dice. You roll double-ones, you die. Anything else, you have infinite prestige and a high level position at half of all engineering firms in the world, for as long as you want.

  11. Great post! Grad school can seem a lot like outer space sometimes… the microgravity environment of the desk and books, offering little chance for weight-bearing exertion; the sunless, vitamin-D depleting laboratory; the immunosuppressive effects of impending exams.

    When I get back to “Earth” after finals, I look forward to my own 4-12 week rehabilitation!

    1. What are you doing for grad school? I’m mech-eng…I feel all the pain you’re going through!

      Not the lifestyle for me…but it might lead to it.

      1. Molecular Toxicology here – I’m hoping for a career that fuels my brain and funds my travels!

  12. If microgravity atrophies muscle and degrades bone density, could we cure people who have developed osteoporosis by putting them in those spinning trainers that get pilots used to high-Gs?

  13. See, what they really need is artificial gravity, inertial dampeners, food replicators, holodecks, universal translators, and a bald man named Jean-Luc in charge.

    I’ve always dreamed of going to space. Still an option for me. I fit the criteria (being primal helps with the fitness criteria), but so do thousands of others. Canada recently recruited 2 astronauts for the newest training program out of a pool of almost 10000 qualified applicants. My physics professor made it into the top 16! Two that made it: air force pilots with PhD’s on the side…

    Tough competition!

  14. Mark – I wonder what you think of elite runners using the Alter-G treadmill that simulates running in lesser gravity. While most of the athletes are running outside for the majority of their volume, are they producing aerobic fitness (from the use of the Alter-G) that can’t be supported by their weaker musculoskeletal system?

  15. Interesting piece. Although I thought it was going to go in a slightly different direction, because many of the health degradations astronauts experience are very similar to those of the many Americans who eat the SAD and don’t exercise: ex. BP and heart rate problems, headaches, bone density loss, difficulty sleeping, immune suppression, etc. Maybe they are all just wannable astronauts 🙂

  16. Great post, made me think about where I live. Currently -30C. I wonder what effect winter has on my body other than limited sunshine…

    1. Mark,

      Great post! As an Exercise Scientist with the Exercise Physiology & Countermeasures Project at the Johnson Space Center in Houston, I can tell you first-hand that your assessment is spot on. We are researching many different things with regards to the development of effective exercise and non-exercise countermeasures, and it is quite a challenge. 🙂 Many times, things that people think should be a no-brainer solution to a problem simply aren’t feasible in a microgravity environment. We are, however, making great progress and continue to learn something new everyday. 🙂 Thanks again for the great post!

  17. I had heard about the bone effects, nice details. Will check references later.

    I read “The Body Electric,” and it mentioned that the cause is most probably the earth’s electromagnetic field, despite it’s very very small magnitude. Think about what else those fields are doing for us.

    Recently a study showed that axons can communicate with each other without any direct contact whatsoever. SOme believe it may have to do with electromagnetism. Maybe I should post links.


  18. Interestingly, there’s also been some research into magnesium losses in space – probably being excreted straight from the bone surface, where most of the body’s magnesium is stored. Without enough magnesium in place, over 300 enzymes (ATP!) start to fail… including those related to glucose metabolism, not to mention ion balance.

    And yes – we are a deeply curious species. And it is both terrifying and wondrous. Thanks, Mark!

  19. I would like to have read more on the vibrating plates as they seem to be the latest fitness craze. How valid are they?

  20. Wow, Mark, what a terrific article!!I didn’t know how ignorant I was about all that you detailed!!! (Too much Star Trek back in the day, LOL) Very informative article, Thank you for taking the time to educate us that didn’t know. and comparing it to our daily routines here…a great eye opener. At 30 I thought I knew everything, now (30 years later) I realized I haven’t even scraped the surface of all there is to know….

  21. A nice eye opening post that was actually imformative. I did not know that gravity itself was causing our bodies to produce muscle building proteins, but hey, you live and you learn right?

  22. I have often thought that gravity must be a real bitch after returning from months aboard the space station…

    fascinating topic, thanks for sharing.

  23. I remember a scifi story by Michael Moorcock in which he blithely notes that space exploration was a big dud because “for unknown reasons” no-one could survive very far from Earth for any length of time. Who knows what subtle influences the planet has that might support life, and without which we simply wither and die? Because of our limited understanding of life and vital forces, it is easy to just blame a lack of gravity – but when you factor in Sunlight, protection from Cosmic Rays, the Magnetosphere, and the subtle energies of a world full of living things, it is perhaps not inconceivable that manned extraterrestrial exploration is not possible without a living spacecraft (i.e. Mother Earth). So much of our casual abuse of this planet is predicated on the “more of that somewhere out there” mentality: if this planet was the ONLY PLACE we could thrive and be healthy, and we knew it, perhaps we would care for it a bit better?

    I think Erwan leCorre’s work dovetails brilliantly with Mark Sisson’s books and e-information: a return to simplicity/sophistication, rather than central control/diktat and regimentation. We need to embrace and recreate the Natural, both in our environment and in ourselves, for optimal Health and happiness – and perhaps we can do it by focussing more on what is within and around us, than some far-flung frontier.

    just my ha’pennysworth!

    1. I remember asking my high school science teacher: If we were on another planet with perhaps a different number of moons, or different gravity, how would that affect things like our menstrual cycle?

      He didn’t know. And we wouldn’t find out until we actually started living on a planet.


  24. Mark has made a very poignant comparison of our manufactured lives with astronauts in space. This is so evident as I type in my sterile office communicating with strangers in “internet land”. I might as well be on a spacecraft as I’m strapped in an uncomfortable chair in an unnatural position. The only “food” available nearby are packaged chips and cookies in a vending machine – all of which could last for a long starfleet voyage. Occasionally I get to glimpse longingly out the window wondering what kind of lifeforms are crawling outside my “spaceship office”. This also holds true for all of our modes of mechanized transport and gymnasiums with treadmills and bizarre exercise machines. Those contraptions would be more at home on the Star Trek Enterprise than here. It’s as if we have created all these artificial environments in anticipation of going out in space as we are so far removed from nature.

    Although we have benefited from research conducted in outer space, it’s ironic how we think all products developed in there are so good for us. People would rather drink a concoction like Tang rather than eating an orange!

  25. I always knew there was a bit of the poet/philosopher in you Mark.

    Interesting article but BEAUTIFULLY written.

    You should consider writing fiction too, if you haven’t already. You have a gift for words to invoke imagery.



  26. I enjoyed your musings on this. i guess not so different to the story of the many adaptations we have made on our long journey down from the trees – we are going to have to send a bunch of us up there in baby steps and see who survives!

  27. The folk working on colonization projects, on the Moon and Mars, have focused their attentions on finding suitable caves to build a colony in. I find that thought strangely comforting. 😉

  28. Extremely interesting, Mark. It dramatically shows how unhealthy it is for human beings to move away from the environment in which we evolved. The implication is that on earth it must also be unhealthy to depart too far from the lifestyle that evolution has adapted us to live. Note the similarity; there are medical interventions to counteract the bad effects of space travel and there are medical interventions to counteract the bad effects of the American lifestyle. We’re not adapted to either.