Can an adult human with no underlying medical conditions survive on these foods alone for 24 months without severe malnutrition?

Here is the list of foods:

  • Water
  • Plain crackers
  • Canned beans

Assume an unlimited amount of these foods. The human must be able to walk and pull a cart containing these foods for 2 years in a Mars-like environment. In addition, could the human fully recover afterward?

  • $\begingroup$ most likely yes $\endgroup$
    – Topcode
    Sep 12, 2020 at 20:47
  • 4
    $\begingroup$ If by "on these foods alone" you really mean nothing else, then the human will very obviously be confronted with a severe lack of fats and vitamin C. Survival is extremely unlikely. If those "canned beans" don't have added salt, then the poor human won't get to experience the effects of the lack of fats and vitamin C -- the lack of sodium will kill him much more quickly. (And the two years in the title have morphed into half a year in the body of the question. There is a great difference between six and twenty-four months.) $\endgroup$
    – AlexP
    Sep 12, 2020 at 21:15
  • $\begingroup$ @alexp now that hes changed it, gotta agree $\endgroup$
    – Topcode
    Sep 12, 2020 at 21:19
  • $\begingroup$ You may want to explain what "plain crackers" are. There is no such food in Europe, or at least I've never seen "plain crackers" for sale; I'm thinking of some sort of hard tack made of flour, water and yeast and double cooked? But it still a mystery. $\endgroup$
    – AlexP
    Sep 12, 2020 at 21:22
  • 1
    $\begingroup$ @Ton Day, 2 years. $\endgroup$
    – Galactic
    Sep 16, 2020 at 4:59

6 Answers 6


If you got some sun you would be ok.

bean vitamins


You will note that for vitamin C the % daily value is 5%. That is % in one serving of beans which is about 200 kcal. If you were living on beans you would eat 10x that much which is 20mg/day; 50% of the recommended daily allowance but enough to not die of scurvy. If you were eating more beans you would get more vitamin C; for example 3000+ kcal/day is reasonable for a person doing physical labor.

Beans (and crackers) have no vitamin D and no B12. It takes 3-5 years to exhaust normal bodily B12 stores so even a diet devoid of B12 would be ok for 6 months or 2 years.

Vitamin D deficiency could get you in trouble but you can synthesize that yourself when sunlight (ultraviolet light actually) hits your skin. If you knew that was an issue and took pains to get some sun then vitamin D would be ok. But even profound vitamin D deficiency is tolerable for adults - it messes with your bones and really that is about it.

  • $\begingroup$ You still have no fats in crackers or beans... $\endgroup$
    – AlexP
    Sep 12, 2020 at 23:17
  • $\begingroup$ @AlexP: The question of fat being necessary aroused some passion on this answer. worldbuilding.stackexchange.com/questions/99766/…. I assert that linoleum and linolenic acids are necessary micronutrients but fat itself is not necessary. We can synthesize fats that we need for the constituents of our bodies. $\endgroup$
    – Willk
    Sep 12, 2020 at 23:34
  • $\begingroup$ @AlexP, the canned beans may be cooked in oil providing fats. $\endgroup$
    – Galactic
    Sep 13, 2020 at 0:55
  • 1
    $\begingroup$ Maybe the subject of this diet could get the required sunshine by tending to a few avocado trees. That would boost the vitamin c, and more than cover the need for fats and vitamin D. $\endgroup$ Sep 13, 2020 at 4:37
  • 1
    $\begingroup$ When I saw the question about canned beans, I immediately thought baked beans, which would contain fats (and often tiny bits of bacon) so to settle this argument, we'd need the specifics of the beans (all kinds of beans = expanded nutrition). A UV light would be a good alternative for Vit D, since it may not be possible to sunbathe on Mars. $\endgroup$
    – DWKraus
    Sep 13, 2020 at 6:20

The character would probably die almost instantly.

The original question asks:

The human must be able to walk and pull a cart containing these foods for 2 years in a Mars-like environment.

Everything that people have suspected about a Mars-like environment in the 20th century, and all they have learned about a Mars-like environment since 1964, says that the atmosphere of Mars has only a tiny fraction of the atmospehric pressure necessary to maintain human life.

A person would loose conssciousness and suffer fatal injuries with seconds of exposure to the Martian atmosphere, or even an atmosphere which was several times as dense as the Martian atmopshere. And the Martian atmosphere has only trace amounts of oxygen, so if it was concentrated to the same pressure as Earth's atmosphere, someone would still suffocate quickly when breathing it.

No environment which is even remotely Mars-like can be survivable for an unprotected human.

So maybe the human is not unprotected. Maybe they wear a full spacesuit when they pull their cart around on the Mars-like surface.

That means that a lot of the space and weight capacity of the cart would have to be used to extract oxygen from the Martian atmosphere or soil somehow to replenish the oxygen supply of the person's spacesuit, and the power source for the oxygen device.

That leaves a lot less room for food in the cart. I believe that I eat several pounds of food and water each week. So for about 2 years or about 100 weeks someone would need a load of several hundred pounds of food and water to carry around in their cart.

So how does the space suit wearing human actually eat and drink the food and water they pull around in their cart? How does the food and water get from outside the spacesuit to inside the spacesuit without the human losing air and dying? And how do they excreate while wearing the spacesuit?

It would be a lot more plausible if the human lived in a pressurized habitat where they didn't have to wear the space suit, and only went on long trips outside the pressurized habitat pulling the cart when they had missions requiring them to be out of the habitat for several days at a time.

I note that in a spaceship or a large habitat in space or on a planet, an advanced enough technology would enable the recycling of all waste products via complex chemical reactions powered by a powerful energy source into breathable air, drinkable water, and nourishing foods.

And possibly after such recycling becomes common in space ships and large habitats, centuries of improvement and advances will enable such recycling equiment and its power source to be miniaturized small enough to be built into a spacesuit, so that someone could survive in a spacesuit for months or years without ever taking it off.

And possibly before that recycling equipment becomes miniaturized enough to be used in a spacesuit, a slightly less miniaturized version would become available which could be installed in a cart pulled by a human in a spacesuit with various umbilical hoses connecting the cart and the spacesuit, so that the cart is effectively a vital part of the spacesuit.

But in that case the recycling system would synthasize air, water, and nutritious foods for the human, and they would not need to carry hundreds of pounds of air, water, and canned(?) food with them in the cart.

As I wrote, any environment which is "Mars-like" would be almost instantly lethal for a human without the protection of a pressurized habitat or a spacesuit.

But possibly the question means an environment with Mars-like gravity for making pulling a cart loaded with years of food in it easier, but with an Earth-like atmosphere which is breathable for humans. Thus the human wouldn't need a spacesuit, heavy oxygen bottles, or a device to extract and concentrate oxygen from the atmosphere or the ground.

And so they might not have devices to recycle wastes into synthasized food, and thus might need to rely on canned(?) food and water supplies which they have to pull behind them in a cart.

But is a planet with low, Mars-like gravity and a breathable atmosphere possible?

The important atributes to consider here are the surface gravity of a planet and its escape velocity.

The surface gravity of the planet should be low enough that movement and pulling heavy loads is much easier than on Earth, while high enough to avoid problems with movement and avoid the long term bad health effects of microbravity.

And the escape velocity of the planet has to be high enough to prevent oxygen and other necessary gases from escaping.

The surface gravity of a planet can be calculated from the equations here: https://en.wikipedia.org/wiki/Surface_gravity#Relationship_of_surface_gravity_to_mass_and_radius[1]

And the escape velocity of a planet can be calculated from the equations here:

https://en.wikipedia.org/wiki/Escape_velocity#From_the_surface_of_a_body 2

And I have noted that for planets, moons, and other objects less massive than Earth, the listed surface gravity decreases faster with a decrease in mass than the escape velocity does, so that the escape velocities of those smaller bodies are higher, proportional to Earth's escape velocity, than their surface gravities are proportional to Earth's surface gravity.

Which helps a bit in having planets with lower surface gravity retain their atmospheres.

There is an estimate about how small a planet could be and still have an atmosphere breathable for humans.

Habitable Planets for Man Stephen H. Dole, 1964, 2007, is a scientific study of the requirements for a planet to be habitable for humans.


Pages 13-19 discuss the atmospheric requirements, and pages 53 to 58 discuss the mass requirements for a planet to retain a breathable atmosphere for geological amounts of time.

On page 54 Dole calculates that the minimum escape velocity for a planet to retain a breathable atmosphere is 6.25 kilometers per second, corresponding to a mass of 0.195 Earth and a surface gravity of 0.49 Earth. But Dole believed such a planet would be too small to produce enough oxygen for humans to breath.

Dole made two different estimates of the minimum mass of a planet that could produce an oxygen rich atmosphere, 0.25 Earth and 0.57 Earth. Dole decided that the correct minimum mass should be between those figures, and thus about 0.4 times the mass of Earth, which corresponds to a planet with a radius of 0.78 Earth radius and a surface gravity of 0.68 Earth.

However, discoveries since Dole wrote indicate that it might, repreat might, be possible for a world with lower surface gravity than that to have a breathable atmosphere.

Titan, the largest moon of Saturn, has a very surprisingly dense atmosphere considering its low surface gravity & escape velocity. Its surface gravity is only 0.36 that of Mars, while its escape velocity is only 0.52 That of Mars. But Titan has an atmosphere many times as dense as that of Mars.

In fact, Titan's atmosphere has a atmopshere 1.45 times as dense as Earth's, despite Titan having a surface gravity 0.137 that of Earth and an escape velocity 0.235 that of Earth.

So perhaps it is possible for a planet to have a surface gravity like that of Mars, temperatures similar to those on Earth, and a breathable atmosphere.

However, part of the reason that Titan has a dense atmosphere is because it is so far from the Sun, and way too cold for unprotected humans to survive. Humans would need very warm clothing to survive on Titan. And while Earth's atmosphere is about 78 % nitrogen and 20.9 % oxygen, Titan's atmosphere is about 97 % Nitrogen and 2.7 % methane, with no oxygen detected. So humans would have to use breathing apparatus on Titan.

Titan offers hope that a planet with Mars-like surface gravity and Earth-like temperatures might have a breathable atmosphere, but not proof that is possible.

Another possibility might be a story set in a vast artificial space habitat, a hollow cylinder which rotates to provide Earthlike gravity.

So perhaps a vast cylindrical space hapibtat has been constructed and has been supplied with an atmosphere, and is being slowly spun to provide Earth-like gravity for the eventual settlers.

But it will take years or decades to get the vast mass spinning fast enough to avoid long term health problems for the settlers, so the station is deserted at the moment.

But maybe two people have snuck into the station to fly with artifical wings attached to their limbs, which is practical near the center axis of a rotating space habitat but not near the surface where the gravity is too high. Inside this station the gravity is not yet too high at the surface for human powered flight, so they can land and take off from the inner surface, which they couldn't do in a habitat ready for occupation.

So maybe the two people are flying low over the surface and can easily land when they want to, unlike in an inhabited habitat, when suddenly some interior storm strikes them and scatters them. They land separately too far apart for each to see or guess where the other has landed, and the protagonist's wings are broken beyong repair.

But the station has a hundred levels of interior space below the inner surface they were flying around above. Those levels wiil be interior spaces for people to live in and for all the food synthiszers and other life suppport equipement which will be installedin the future. The surface area will be reserved for parks and other recreational purposes.

Those lower levels were built in many thousands of airtight segments that were joined together to form the giant cylinder. And the airtight airlock doors between each segment are locked and won't be unlocked until the station is made ready for habitation.

And the protagonist knows that there are emergency supplies in each segment for workers who might be stranded due to accidents.

So he opens a door to a ramp down into the lower levels, and finds the emergency cache, which is in the same location in every one of the shousands of segements. He finds a cart and loads it up with all the water and food he can pull in the very light gravity, leaves a note for anyone who might happen to come there, and pulls the cart back up the ramps to the inner surface of the cylinder.

And then he sets out across the inner surface until he reaches one of the ends of the cylinder. Then he pulls the cart up ramp after ramp after ramp, the elevators probably not being powered yet, up kilometers to the central axis of the habitat, where their space ship is parked. His partner isn't there.

He waits for the partner as long as he can stand to, and then leaves a note at the spaceship and returns to the inner surface of the cylinder. And then he searches the inner surface of the cylinder for his partner who could be dead or injured, and goes down to the emergency supply place in each seqment, checks to see if any supplies have been taken, and leaves a note for anyone who might find it.

And it may take him years to search the entire habitat, replenishing his supplies from the emergency supply places, until he either finds his partner or the work crews arrive to begin readying the habitat for the colonists.

And this is the best I can think of to justify someone pulling a cart loaded with food and water through a "Mars-like" enviroment.

  • 2
    $\begingroup$ The problem doesn't say he doesn't have a suit. This appears to be a The Martian type scenario. $\endgroup$ Sep 13, 2020 at 22:27
  • $\begingroup$ Thank you! I laughed so hard, my face hurts. $\endgroup$
    – Otkin
    Sep 14, 2020 at 1:09
  • 1
    $\begingroup$ The answer is sooo long that I have run out of air midway. And what's worse is I had no crackers :D. $\endgroup$ Nov 18, 2020 at 11:08
  • $\begingroup$ @LorenPechtel A suit is one thing but 2 years worth of oxygen is another. The question definitely implies he has the cart and only a cart with no base, otherwise why would you drag 2 years worth of food around on a cart everywhere you go? Where is the 2 years worth of oxygen coming from? The tanks to store that are going to be heavier than the food. $\endgroup$
    – DKNguyen
    Nov 19, 2020 at 21:37
  • $\begingroup$ @DKNguyen Maybe the suit manufactures the oxygen on the fly. Quit possible if you have a handwavium power source for it. $\endgroup$ Nov 19, 2020 at 23:04

Most likely.... But you need to think about the deficiency on Vitamin D.

Above the Earth’s atmosphere the solar irradiance is slightly more than 1300 watts per square metre. The Earth’s atmosphere is not perfectly transparent to sunlight and about 1/4 of the Sun’s light scattered before it reaches the surface.

At Earth’s surface, with the Sun directly overhead at local noon (clear dry atmosphere), the solar irradiance is reduced to 1000 watts per square metre. This value is highly variable depending upon such things as the amount of dust and water vapor in the atmosphere.

At local noon on Mars, with Sun directly overhead, the solar irradiance 590 watts per square metre.

Mars atmosphere is very light, like 0.5% as of earth with no ozone layer. So, there are too much UV rays that will burn a space traveller skin quickly. And if they can have enough protection, rickets will quickly affect them and their bones will be weak. So they will need Milk for getting Vitamin D.

Plain crackers and Canned beans (if cooked in oil) will provide fat.

  • $\begingroup$ Milk does not naturally have enough Vitamin D for a human. Milk was merely used as the most convenient food to supplement. $\endgroup$
    – Mary
    Nov 18, 2020 at 13:35

Crackers and beans are, imho, not very healty food, lack of vitamins, too many plant protein from beans with absense of dietary fibres (from fruits and vegetables). I think your character can have dramatic stomach problems from diet like this. But if we consider character found stash of Military Grade Emergency Rations (each of them have enough food to keep grown up human for full day), things are not so dramatic.

Lets consider this tourist grade ration: tourist grade food ration

Kits like this are popular among Russian hikers. It has various porridges with meat, preserved vegetables, dried bread, some snaks and food warming systems. Water not included. All this kit weights around 4 lb or 1.5 kg. So, to survive 6 month, character needs 6*30 = 180 kits, or 270 kg / 720 lb of this kits. Its possible to carry all this weight in hand pulled cart. If we had Mars like environment with lower gravity, task is much easier.

But, humans requires ~ 2-3 kg of water per day, so your character needs big flask and access to drinkable water sources once per few days.

Also, humans requires oxygen. And there is no oxygen in Mars atmosphere.

  • 1
    $\begingroup$ Do you mean dietary fibre when you say cellulose? $\endgroup$
    – Otkin
    Sep 13, 2020 at 18:44

If this is a survival mode with a lot of physical activity, exposure to the sun, then you can survive with one type of food. Moreover, the brain involved in nutrition accepts that this is the only way to get energy. Ultimately, this will change our body structure and how the brain works differently.

But if there are other food options, it's very difficult to convince the brain. Moreover, in order to think, learn and behave in today's social conditions in an extremely competitive world, all nutrients are needed in order to cope with others.

In this article, it is said that malnutrition of your daily allowance for a long time will definitely cause micronutrient deficiency. When the body does not get enough essential vitamins and minerals from food. Micronutrient deficiencies can impair health and development.

  • 1
    $\begingroup$ The initial part of your answer seems to contradict the last part. What is your real answer? $\endgroup$
    – L.Dutch
    Nov 18, 2020 at 10:40

Survival is impossible:

By "plain crackers" I assume soda crackers. Vitamin A = 0. Beans, Vitamin A = 0.


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