Could our digestive system handle alien meat?

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In lots of sci-fi desperate survivors often eat native creatures on alien planets. Besides the obvious dangers like it having poison sacks or something, what would happen if we tried to eat it? Is our digestive system tied closely to the evolution of Earth life, or would it universally be able to break down at least some of the nutrients? Let's assume that the life is amino acid based and has been thoroughly cooked.
 
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A well-equipped ship or escape pod would have a lab to test anything before eating. The nutrients and trace elements would be an issue, I think.
 
Since we are speaking of hypotheticals, if amino acid based life exists outside of Earth, then the most likely places where they would exist would be on planets with a similar composition to Earth (e.g. existence of an atmosphere, presence of water, breathable air consisting of oxygen, etc.) If such life with a certain degree of complexity exists, then presumably they would have evolved with its basic components having similar molecular structures as life on earth, and presumably these life would need to seek sustenance in a manner similar to life on Earth (i.e. consuming other forms of life).

If so, and since we humans are after all just another animal (hence just another form of life), at least in theory we should be able to consume life that has evolved in Earth-like planets (with the obvious caveat of certain lifeforms containing poisons, etc.) That being said, given that we would be unfamiliar with such life, it would be a considerable risk to try to consume other life without knowing more about the chemical composition of such life, and whether such life would be safe to eat.
 
There are many forms of life here on Earth which if eaten by humans are toxic, and in some cases lethal even in small quantities.
Ideally the colonisers would be able test the effects of eating the alien life on lab rats or similar at first.
If not then the only way to find out would be for a human to risk consumption of a very small amount, and if no problems test larger amounts.

It would be more likely though that a colony would include seeds of crops which grow on Earth.
Making adequate soil for them to grow on an another world may be less challenging.
 
There are two questions wrapped in one: would such food be toxic, and would such food be nutritious. For example, a creature that used sucralose instead of sucrose wouldn't do you much good if you were to eat it.

While we don't know the answer to either question, I suspect that alien food would be dangerous even if the chemistry were similar to our own. The reason? Minerals. Too little selenium, we die. Too much selenium, we die. Same story with copper, iodine, potassium, manganese, cobalt, etc. The odds that the balance of these elements on some other planet exactly balances the range on Earth seems unlikely.
 
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I wrote a short story once about a guy who built a robot to test food for him when he visited alien planets. At the first planet he finds he give the robot a piece of fruit and has it test the item. He'd seen the local birds eating the fruit, but wanted to make sure.

"Is it safe to eat?"

"Yes."

The human eats the fruit and gets extremely sick.

"I thought you said this was safe to eat!"

"I didn't say for whom."

As he lays dying the man thinks "This is what I get for programming that thing in C."
 
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I would think it unlikely, even if the fundamental biomolecules of the alien world were similar (amino acid proteins, DNA, lipids etc) there's a vast range of possible configurations that are different to our own. Highly conserved proteins for this world may include features that our digestive enzymes cannot cleave, e.g. if their version of collagen is highly cross-linked or if cellulose-like cell walls were the norm in most kingdoms. We see this to some extent on Earth with enzymes that are homologous across species.

There's also the risk that with such a similar biochemical make up something in the environment (or many things) would be antigenic. Infection by bacteria, virus or other pathogen seems unlikely (in absence of a history of host/pathogen co-evolution) but you may still end up with dangerous allergic reactions.
 
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One thing for sure, they would find out the hard way if it was toxic. It could also be long term carcinogenic which would only be found years later even if proven not to be immediately toxic.
 
I'd imagine the risks would not be entirely unlike those experienced by humans in unfamiliar Earth environments. It would be a trial and error process limititing consumption to things observed to be eaten by the local fauna, or, preferably, your bolder companions, which is how human food sources were 'discovered' by our ancestors. Natural selection would arbitrate the wisdom of food choices. To paraphrase a popular pilot saying, there are no old bold ancestors.
 
There's one BIG caveat about all the following items. I'll describe that caveat near the end.

Sugars: There's a reason nature chose glucose and fructose as the most common sugars - it's because they're the most stable forms of six carbon sugars. If you were to eat alien fruits there's a good chance you would run across a high proportion of these sugars, as well as sucrose which is a combination of glucose and fructose.

Fats: The development of phospholipids from simple fatty acid membranes is a logical evolutionary development that created a membrane that was much more impermeable to ions and thus much more efficient for cell energy management. For this reason it is fair to assume phospholipids could be found in alien cells. Triglycerides, which are used for storing energy, are a logical development that stems from these phospholipids so there's good chance you'd find those as well. However for both phospholipids and triglycerides there's a wide variety of forms and so I'd predict you'd only be able to utilize a small proportion of them.

Proteins: The good news: Protein (chains of amino acids) is such a ubiquitous and useful polymer here on Earth that I'm willing to bet the farm that any particular alien life form will utilize it as well. There's also reason to think that at least half of our standard 20 amino acids could be found in alien bodies - mainly because they're some of the simplest amino acids. The other half is really uncertain though, and some of them like histidine seem extremely unlikely.

The bad news is that the enzymes in our digestive systems would likely only be able to break apart most proteins into larger chunks by breaking the peptide bonds. All of the specialized proteins we have for separating specific amino acid combinations as well as breaking down other familiar combinations would likely be useless or close to useless. I'm guessing we'd only be able to extract about 5% of the amino acids from any alien protein.Vitamins:
Niacin can be found in meteors. It is also a very simple molecule and many scientists believe it was the very first vitamin/coenzyme. There's probably a good chance you'll be able to get this from aliens.

Vitamin C is an extremely useful and fairly straightforward coenzyme derived from sugars, there's probably a pretty good chance you'll be able to find that as well.

B6: This is a simple molecule and there's a small but real chance you'd find it in alien food matter.

For the rest of them there's a variety of reasons to think that there's only a very small chance of finding them in alien flesh. Some, like B12, are ridiculously unlikely.Caveat: All of these biomolecules can exist in either a 'right-handed' or 'left-handed' form (except for the amino acid glycine). All of our digestive enzymes are designed specifically for one of these configurations. If we were to encounter the opposite configuration we wouldn't be able to break them down hardly at all. Just through natural chemical processes however (high acidity in the stomach for example) I believe there would be a tiny proportion that would break down into small enough biomolecules such that we could eat consume them.

There's some evidence to suggest that the earliest amino acids on Earth were skewed slightly towards left-handed (our current configuration) so we'll say there's slightly better than 50% chance that you'll find alien amino acids to be digestible. You could probably flip a coin for the other types of biomolecules.Final summary: Both you and the bacteria in your digestive system would only likely be able to extract a small proportion of calories from the food you eat. The bacteria that came with the alien flesh however would have no problem eating it and thus would turn your digestive system into a festering tube of putrid and decaying flesh. This would be IBS times 50. The resulting horror would likely make you think fondly of starvation.

If you were to continue on this emergency diet you would also start to get nutrient deficiencies (amino acids, linoleic acid, linolenic acid, vitamins) within about 4 to 5 days. After about 3 weeks these deficiencies would likely kill you.

So yeah, best plan ahead :)
 
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Should be alright if you cook / boil it first, unless they are Tardigrades with five billion years of evolution designed specifically to eat your germs!
 
Are we talking about long or short duration? With most vitamins, you can go a month without them and live. If you are stranded for a month, you should be able to get adequate nutrition out of the plants and animals. There are many chemicals in a body and I'm inclined to think that at least one of the chemicals in an alien body would be toxic to us. If you figure out which chemical it is, you might be able to neutralize it. The spaceship might have a food processor that adds vitamins and deletes toxins. Carpenter ants feed leaves to fungus and eat the fungus. We might be able to do the same thing on an alien planet.
 
tkyoung75 said:
Should be alright if you cook / boil it first, unless they are Tardigrades with five billion years of evolution designed specifically to eat your germs!

Not true. Boiling does not turn incompatible proteins and other molecules into ones compatible with your biology nor does it neutralize all poisons.

Phineas Far said:
Are we talking about long or short duration? With most vitamins, you can go a month without them and live. If you are stranded for a month, you should be able to get adequate nutrition out of the plants and animals. There are many chemicals in a body and I'm inclined to think that at least one of the chemicals in an alien body would be toxic to us. If you figure out which chemical it is, you might be able to neutralize it. The spaceship might have a food processor that adds vitamins and deletes toxins. Carpenter ants feed leaves to fungus and eat the fungus. We might be able to do the same thing on an alien planet.

That would be very unlikely. The chances of alien biology being compatible with our own is remote, as has been explained in several posts above.
 
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Phineas Far said:
Are we talking about long or short duration? With most vitamins, you can go a month without them and live. If you are stranded for a month, you should be able to get adequate nutrition out of the plants and animals. There are many chemicals in a body and I'm inclined to think that at least one of the chemicals in an alien body would be toxic to us. If you figure out which chemical it is, you might be able to neutralize it. The spaceship might have a food processor that adds vitamins and deletes toxins. Carpenter ants feed leaves to fungus and eat the fungus. We might be able to do the same thing on an alien planet.
I'm talking about extreme short term. A crashed ship with a stranded crew. Help is weeks away but not years.
 
One thing that is very plausible is engineering gut bacteria to break down and partially digest alien biological matter. They'd take a portion and you'd take a portion, similar to the way ruminants digest cellulose via anaerobic bacteria in their digestive tracts. Under focused, guided artifical selection you could probably come up with strains that could break apart nearly all alien biological molecules. So those fictional scenarios where humans survive on alien flesh could occur with sufficient foresight.
 
NC_Seattle said:
So those fictional scenarios where humans survive on alien flesh could occur with sufficient foresight.

Sure. Given sufficient foresight and technology this would almost certainly not be an issue.
 
NC_Seattle said:
Caveat

I got your "caveat" right here :wink:

 
I couldn't find a peer reviewed publication for this question and therefore all responses here are probably speculative.

This is the best I could do, but I'm sure it's not approved by the US Food and Drug Administration.

http://www.ufopaedia.org/index.php/Alien_Food
 
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We won't know until we try it, but my general feeling is that it would generally not be safe to eat the plants, generally safe to eat the animals, but with a 50% chance that the alien biochemistry uses the other handedness, so they'd have negligible nutritional value.
The difference is that animals defend themselves from being eaten by running away or fighting back, but plants defend themselves by incorporating toxins. Because we evolved in the presence of some of these toxins, we've evolved tolerance to many of them, but if you found yourself lost in an Earth jungle, it would be unwise to eat any plant that you didn't recognise.
 
Alice in Through the Looking Glass also wondered if looking-glass milk wasn't good to drink because it was flipped to its opposite handedness.

(its a publication and its been reviewed)!
 
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We did evolve on Earth to digest certain things, like western people used to be lactose intolorent and struggled to digest cows milk years ago. But the thing is in sci fi, we completely base alien life on what we might expect or imagine. There isn't anything remotely scientific about these fictional creatures, in fact we have a tendency to base them on our own experience of what we class as a life form. But if we assume that an alien has what we would consider meat, there is absolutely no way of telling until we tested it. No way whatsoever, we either have to imagine that it has digestable properties, or non digestable properties, its all strictly down to the imagination, there is no known alien life form to base a conclusion on.

I would love to reach a point where we find out though
 
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Adamchiv said:
I would love to reach a point where we find out though
Yes. it's the biggest of all questions, well for me it is.
Is what happened on Earth really unlikely, but then it did?, or is life in some form, even simple life, something that inevitably takes off given the right conditions.
 
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Yes I agree in my opinion its the most fascinating question. I don't believe it is as unlikely as some people think, carbon is very abundent in the universe and incredibly fertile. So their must be another lifeform on a goldilocks planet somewhere. Probably in our own galaxy! Dont want to sound unscientific, I admit I am purely speculating