I think chance that alien food would actually be edible to us to the extent you can actually live off it as a food source without supplements is rather low. A bit like expecting to be able to survive on eating petrol. Even if it is organic, it's not going to have what a human needs to survive (though some microbes may be able to make use of it).
It could be poisonous or it could be just pointless, like trying to eat sand, goes through your body and is rejected.
This is improves the situation a lot, and is not impossible especially for nearby stars, or indeed life in our solar system. E.g. hypothesis that life on Earth originated around another star and you find another planet seeded by the same star - then it could still be deadly.
In that case, it could potentially be nutritious to us. But just like many Earth life, and more so, it could also be harmful.
For instance, it could cause an allergic reaction Allergy causes
Or indeed, many Earth berries are food for some animals but poisonous for humans. E.g. "deadly nightshade" or wisteria seeds.
If your host is gobbling down some tasty berries or seeds, even if they are an Earth species, actually evolved here on the Earth, doesn't at all mean it is safe to eat for you. Even on the Earth if, say, a parrot is gobbling down tasty seeds, it doesn't mean they won't kill you. 11 Toxic Wild Plants That Look Like Food
Unless, that is, you are both results of seeding by the extraordinarily advanced Star Trek Ancient humanoids :).
Here particularly talking about proteins. And for humans eating, not other animals or plants, especially microbes, who are less picky feeders, some of them can make do with just water and CO2 and sunlight and a few trace elements :).
So, humans need amino acids to stay healthy. When we digest food, any proteins are broken down first into polypeptides, then peptides, then into their component amino acids. Protein Digestion and Absorption Process - Video & Lesson Transcript | Study.com
So what matters are what the amino acids are in the food.
There are nine essential amino acids that humans need in their food. Essential amino acid
The thing is, that there are an estimated around 4,000 possible biologically reasonable amino acids in one computer search. Alien Life Could Use Endless Array of Building Blocks. And many of them occur in nature. So the number of choices of amino acids to build proteins from, ignoring chirality, and assuming that you have 23 of them (Amino acid) is 4000 choose 23 - or about 10^60.
Of course many of those won't occur in nature, and other searches might change or refine those numbers - but certainly are many more than are used in life, the meteorites have many amino acids not found in nature, and no particular reason to use the 23 ones used by life arising from our genetic code.
For instance, 52 amino acids identified in the Murchison meteorite. Amino acids in meteorites and 52 choose 23 is still 10^14 possible "languages" that life could use to build proteins.
And if you choose 23 amino acids at random from 52, what's your chance that you include all 9 of the essential amino acids?
(Of course also no particular reason why your exobiology has 23 amino acids either, could be any number).
So, the food is likely to be missing essential amino acids, and include extra amino acids that our body is not used to.
And then any of those amino acids can be in either its left or right form to build the proteins. And as likely or not can't be used by the body if you get the mirror image. So chance of all 9 essential amino acids being the correct enantiomer, even if they are all present, is 1 in 2^9 or one in 512.
From John H. Chalmers' answer:
Humans also have many other essential nutrients e.g. vitamins, that have to be in our food or eventually we'll die. Essential nutrient
He suggests, essential nutrients for our ETs, there equivalent of our vitamins, may also be Antimetabolites for us - drugs that interfere with the normal functioning of the cell. And I suppose also vice versa, our vitamins might interfere with their metabolism equally.
So, unless related to us, it's not going to be able to give us all the amino acids we need to survive, bar an extraordinary coincidence.
But apart from that - barring an extraordinary coincidence, it wouldn't have toxins that are targeted at humans or animals specifically.
But there are many things that are poisonous for us, so it doesn't need to specifically target vulnerabilities in humans to do that.
Also, it could have toxins for us that are food for ETs. For instance, maybe your ET just loves to eat hydrogen cyanide, or arsenic, these are delicacies for them, but deadly to us.
Apart from that - well it could be tasty even if not actually nutritious. And it could have carbohydrates to give you energy.
Sugars seem quite possible.
Glucose, the form of sugar you have in fruit juice,
Seems reasonably possible they'd have something like that, simple carbohydrates that we may be able to eat. So you'd be able to use ET food as a source of energy at least.
As other possibilities, maybe it naturally produces an artificial sweetener, e.g. Aspartame which is a combination of two amino acids.
Or Saccharin
Or lead acetate, which of course would give you lead poisoning if you used it a lot.
See Sugar substitute
Ethanol is simple enough, so good chance you can at least share a drink with your hosts, if they happen to also like alcohol (of course depends on their metabolism)
Romulan Ale
But tasting nice is no guarantee that it is good for you, or indeed not poisonous. E.g. antifreeze, Ethylene glycol, tastes sweet.
And is so simple you can easily imagine an ET food including it, and causes Ethylene glycol poisoning
Of course also salt is tasty - sprinkling ET originated salt (maybe with trace elements) on your food might well be fine unless it contains mercury, arsenic or some such.
So there might well also be tasty condiments from ET planets.
It could also contain chemicals that are similar enough to ones our body uses that it takes it up as food - but they are not quite identical.
Example:
L-serine, resembles
BMAA which is created by green algae.
It’s been suggested that BMAA can be misincorporated to cause tangle diseases like Alzheimers.
So - if it is similar enough so that you find it tasty - might be that your predilection for ET food gives you Alzheimers in your later life.
As well as that, you'd need to be sure to sterilize the food because the biggest danger I think would be from ET microbes. Which you might also get from the ETs themselves.
You might think that ET microbes would have no effect on a human, but the thing is - that though they wouldn't be adapted to us, our immune system also wouldn't be adapted to them. Just as you can have e.g. artificial implants that your body doesn't reject because it doesn't trigger your immune system, so also ET life could quite possibly invade your body and your immune system doesn't even notice it because it doesn't produce the chemicals characteristic of life.
So - after visiting an ET and sharing a meal with them, your lungs, sinuses, eyes, stomach, the surface of your skin, and every accessible part of your body may be inhabited by trillions of ET microbes that your body has no idea needs to be eliminated. Microbes that are used to living on the skin and inside the stomach etc of an ET host that has a different biology from you.
And of course would be the same likewise for them, they'd surely find that at least a few of the hundred trillion microbes in ten thousand species that make human bodies their home have jumped over to them and are inhabiting their body as well.
Then these microbes themselves may make various chemicals that are toxic to them and their microbes may make chemicals toxic to you. Or interfere with your body functions. Or even just slowly eat you, if you are edible to the microbes, and your cells don't realize what's going on, they respond to the trauma but their reaction has no effect on the ET microbes.
If the ETs are like some plants and can be sterilized as seeds, then grown in abiotic conditions from then on, (so long as you supply the right nutrients artificially) they probably sterilize themselves of all microbes before encounters with beings from other planets (including of course any microbes they picked up from visits to previous planets).
It might also be that some ETs belong to other "kingdoms of life" that we don't have here, that for one reason or another, like plants, though complex in structure, don't need to have lots of symbiotic microbes to keep alive.
Apart from that, I think that most ETs would use robotic avatars when meeting other ETs "in the flesh" for the first time.
For some reason I don't think any of these movies that depict ETs suggest any problems at all with ET microbes. After all they are written by movie script writers not scientists.
And - you get a kind of evolving "Movie reality consensus" where people accept things in movies because they have been exposed to them in previous movies so evolving idea of what an ET encounter might be like by building imagination upon imagination which probably gets us further and further away from what the reality would be like. Especially since there have been no actual ET contacts to build on to get a more accurate picture in the movies.
For more on possibilities for ET biochemistry (though covering non Earth type planets as well) see
As Philae Awakes - Where Might Life Hide In Our Solar System?
Note, I've now written this up as an answer on Science20:
What Food Can You Safely Share With An ET?
which has some extra material in it which I'll probably copy back here when I get a bit more time. E.g. looks into herbivores and fructivores and gastroliths to name a few.
You can now get this as a kindle book along with many other of my answers, in
Simple Questions - Surprising Answers - In Astronomy
WHAT IF IT HAS A COMMON ORIGIN WITH EARTH LIFE
This is improves the situation a lot, and is not impossible especially for nearby stars, or indeed life in our solar system. E.g. hypothesis that life on Earth originated around another star and you find another planet seeded by the same star - then it could still be deadly.
In that case, it could potentially be nutritious to us. But just like many Earth life, and more so, it could also be harmful.
For instance, it could cause an allergic reaction Allergy causes
Or indeed, many Earth berries are food for some animals but poisonous for humans. E.g. "deadly nightshade" or wisteria seeds.
If your host is gobbling down some tasty berries or seeds, even if they are an Earth species, actually evolved here on the Earth, doesn't at all mean it is safe to eat for you. Even on the Earth if, say, a parrot is gobbling down tasty seeds, it doesn't mean they won't kill you. 11 Toxic Wild Plants That Look Like Food
Unless, that is, you are both results of seeding by the extraordinarily advanced Star Trek Ancient humanoids :).
Some of this food could easily be toxic to humans, or vice versa, even if we are all biologically closely related. In the Star Trek universe then they have an underlying hypothesis that all the planets with the various humanoids on them were seeded by the Ancient humanoids, so it's reasonable that it is all using the same amino acids as Earth life. Could be the same if there's a common origin because e.g. the life originated on another planet around an earlier star that passed through the protoplanetary disks of the forming solar systems.
In Star Trek they go one step further (rather improbably) that the humanoids are so closely related they can actually interbreed, which would suggest that they can eat just about anything we can. Still, even then, they need to take some care. Humans vary a fair bit in their tolerance to foods and in allergic reactions that can be deadly. A Thanksgiving Look At Great Meals In Star Trek History
WHY NOT LIKELY TO BE EDIBLE BY HUMANS IF INDEPENDENTLY EVOLVED
Here particularly talking about proteins. And for humans eating, not other animals or plants, especially microbes, who are less picky feeders, some of them can make do with just water and CO2 and sunlight and a few trace elements :).
So, humans need amino acids to stay healthy. When we digest food, any proteins are broken down first into polypeptides, then peptides, then into their component amino acids. Protein Digestion and Absorption Process - Video & Lesson Transcript | Study.com
So what matters are what the amino acids are in the food.
There are nine essential amino acids that humans need in their food. Essential amino acid
The thing is, that there are an estimated around 4,000 possible biologically reasonable amino acids in one computer search. Alien Life Could Use Endless Array of Building Blocks. And many of them occur in nature. So the number of choices of amino acids to build proteins from, ignoring chirality, and assuming that you have 23 of them (Amino acid) is 4000 choose 23 - or about 10^60.
Of course many of those won't occur in nature, and other searches might change or refine those numbers - but certainly are many more than are used in life, the meteorites have many amino acids not found in nature, and no particular reason to use the 23 ones used by life arising from our genetic code.
For instance, 52 amino acids identified in the Murchison meteorite. Amino acids in meteorites and 52 choose 23 is still 10^14 possible "languages" that life could use to build proteins.
And if you choose 23 amino acids at random from 52, what's your chance that you include all 9 of the essential amino acids?
(Of course also no particular reason why your exobiology has 23 amino acids either, could be any number).
So, the food is likely to be missing essential amino acids, and include extra amino acids that our body is not used to.
And then any of those amino acids can be in either its left or right form to build the proteins. And as likely or not can't be used by the body if you get the mirror image. So chance of all 9 essential amino acids being the correct enantiomer, even if they are all present, is 1 in 2^9 or one in 512.
OTHER ESSENTIAL NUTRIENTS
From John H. Chalmers' answer:
Humans also have many other essential nutrients e.g. vitamins, that have to be in our food or eventually we'll die. Essential nutrient
He suggests, essential nutrients for our ETs, there equivalent of our vitamins, may also be Antimetabolites for us - drugs that interfere with the normal functioning of the cell. And I suppose also vice versa, our vitamins might interfere with their metabolism equally.
IF IT IS NOT RELATED TO EARTH LIFE
So, unless related to us, it's not going to be able to give us all the amino acids we need to survive, bar an extraordinary coincidence.
But apart from that - barring an extraordinary coincidence, it wouldn't have toxins that are targeted at humans or animals specifically.
But there are many things that are poisonous for us, so it doesn't need to specifically target vulnerabilities in humans to do that.
Also, it could have toxins for us that are food for ETs. For instance, maybe your ET just loves to eat hydrogen cyanide, or arsenic, these are delicacies for them, but deadly to us.
COULD BE TASTY HOWEVER
Apart from that - well it could be tasty even if not actually nutritious. And it could have carbohydrates to give you energy.
SWEETENERS
Sugars seem quite possible.
Glucose, the form of sugar you have in fruit juice,
As other possibilities, maybe it naturally produces an artificial sweetener, e.g. Aspartame which is a combination of two amino acids.
Or Saccharin
Or lead acetate, which of course would give you lead poisoning if you used it a lot.
See Sugar substitute
ALCOHOL
Ethanol is simple enough, so good chance you can at least share a drink with your hosts, if they happen to also like alcohol (of course depends on their metabolism)
TASTY POISONS
But tasting nice is no guarantee that it is good for you, or indeed not poisonous. E.g. antifreeze, Ethylene glycol, tastes sweet.
OTHER CONDIMENTS
Of course also salt is tasty - sprinkling ET originated salt (maybe with trace elements) on your food might well be fine unless it contains mercury, arsenic or some such.
So there might well also be tasty condiments from ET planets.
COULD CAUSE ALZHEIMERS OR OTHER TANGLE DISEASES
It could also contain chemicals that are similar enough to ones our body uses that it takes it up as food - but they are not quite identical.
Example:
L-serine, resembles
BMAA which is created by green algae.
It’s been suggested that BMAA can be misincorporated to cause tangle diseases like Alzheimers.
So - if it is similar enough so that you find it tasty - might be that your predilection for ET food gives you Alzheimers in your later life.
BE SURE TO STERILIZE YOUR FOOD AND NOT SIT IN THE SAME ROOM AS YOUR ET HOST - BEST - USE TELEROBITIC AVATARS
As well as that, you'd need to be sure to sterilize the food because the biggest danger I think would be from ET microbes. Which you might also get from the ETs themselves.
You might think that ET microbes would have no effect on a human, but the thing is - that though they wouldn't be adapted to us, our immune system also wouldn't be adapted to them. Just as you can have e.g. artificial implants that your body doesn't reject because it doesn't trigger your immune system, so also ET life could quite possibly invade your body and your immune system doesn't even notice it because it doesn't produce the chemicals characteristic of life.
So - after visiting an ET and sharing a meal with them, your lungs, sinuses, eyes, stomach, the surface of your skin, and every accessible part of your body may be inhabited by trillions of ET microbes that your body has no idea needs to be eliminated. Microbes that are used to living on the skin and inside the stomach etc of an ET host that has a different biology from you.
And of course would be the same likewise for them, they'd surely find that at least a few of the hundred trillion microbes in ten thousand species that make human bodies their home have jumped over to them and are inhabiting their body as well.
Then these microbes themselves may make various chemicals that are toxic to them and their microbes may make chemicals toxic to you. Or interfere with your body functions. Or even just slowly eat you, if you are edible to the microbes, and your cells don't realize what's going on, they respond to the trauma but their reaction has no effect on the ET microbes.
ETS THAT MAY BE CAPABLE OF BEING STERILIZED OF HARMFUL LIFE FROM THEIR PLANET
If the ETs are like some plants and can be sterilized as seeds, then grown in abiotic conditions from then on, (so long as you supply the right nutrients artificially) they probably sterilize themselves of all microbes before encounters with beings from other planets (including of course any microbes they picked up from visits to previous planets).
It might also be that some ETs belong to other "kingdoms of life" that we don't have here, that for one reason or another, like plants, though complex in structure, don't need to have lots of symbiotic microbes to keep alive.
OTHERWISE, ROBOTIC AVATARS
Apart from that, I think that most ETs would use robotic avatars when meeting other ETs "in the flesh" for the first time.
EVOLVING MOVIE CONSENSUS
For some reason I don't think any of these movies that depict ETs suggest any problems at all with ET microbes. After all they are written by movie script writers not scientists.
And - you get a kind of evolving "Movie reality consensus" where people accept things in movies because they have been exposed to them in previous movies so evolving idea of what an ET encounter might be like by building imagination upon imagination which probably gets us further and further away from what the reality would be like. Especially since there have been no actual ET contacts to build on to get a more accurate picture in the movies.
SO IN SHORT
- ET food just possibly might be nutritious if we have a common ancestor
- Otherwise, almost certainly missing essential amino acids - take along food supplements
- Could be sweet though, and able to use it as a source of energy.
- May well be poisonous even if we have a common ancestor
- Tasty doesn't mean it is safe
- Could easily have tasty condiments and some of them might be safe for humans
- Whatever you do, sterilize the food and make sure you have a microbial barrier between you and your hosts, or better, use telerobotic avatars - until you have analysed the trillions of microbes that live on their bodies and shown they are harmless to humans, and vice versa.
For more on possibilities for ET biochemistry (though covering non Earth type planets as well) see
- The Limits of Organic Life in Planetary Systems (National Research Council)
- Hypothetical types of biochemistry (wikipedia)
- Cosmic Biology: How Life Could Evolve on Other Worlds, Louis Irwin and Dirk Schulze-Makuch
- Many Chemistries Could Be Used To Build Living Systems, William Bains
- Life as We Do Not Know It: The NASA Search for (and Synthesis of) Alien Life - Peter Ward
- Weird Life: The Search for Life That Is Very, Very Different from Our Own - David Tooney
As Philae Awakes - Where Might Life Hide In Our Solar System?
Note, I've now written this up as an answer on Science20:
What Food Can You Safely Share With An ET?
which has some extra material in it which I'll probably copy back here when I get a bit more time. E.g. looks into herbivores and fructivores and gastroliths to name a few.
You can now get this as a kindle book along with many other of my answers, in
About the Author
Robert Walker
Writer of articles on Mars and Space issues - Software Developer of Tune Smithy, Bounce Metronome etc.Studied at Wolfson College, Oxford
Lives in Isle of Mull
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