Uh, do not need answer fast >_>
If you’re thinking of chocolate, it’s poisonous to humans, too. It’s not as poisonous to us, but the biggest differences are just due to humans mostly being larger than dogs, and exerting greater restraint in how much we eat at once. A dog, given the opportunity, will eat five pounds of chocolate at one sitting, while a human with twice the mass wouldn’t eat ten pounds at once.
Other human foods which are no-nos for dogs, like onions and most dairy products, just cause really bad indigestion and gas in them.
dogs will eat rotten stuff and shit. since they have a fast throughput because of what their natural diet is then it doesn’t bother them. humans having a slower digestion would get sick from some of the same.
Dogs and humans alike can eat rotten stuff. In both cases, sometimes it works out OK, and sometimes the one doing the eating gets sick from it.
Dogs seem to be able to enjoy salt water without negative consequence.
Let’s remember about eating rotten stuff that even vultures prefer their food fresher, although they have titanium intestinal systems by comparison to humans.
What are these “many” human foods that are poisonous to dogs?
How well do dogs metabolize alcohol? I’ve seen a dog put away quite a few crème de menthes at a Christmas party and still be able to drive.
Brownies, cookies, hot dogs, pizza, sammiches and the food that belongs to the cat. Of those, the most dangerous for the dog is the food that belongs to the cat, which can lead to acute claw poisoning so fast it will make your head spin. The others just give the dog a facial expression that would be extreme guilt if on a person.
I was interpreting “poisonous” to me “lethal”, but I guess that was incorrect…?
Well, methanol poisoning can cause permanent vision loss. And I’ve seen dogs who have lost eyes from sampling cat food.
Not really. Different animal species metabolize digested food differently, and use different pathways to clear and metabolize them. Some use some pathways more efficiently than others. Dogs, cats, and people do not metabolize what they eat the same way. Their liver (and other organs as well) react slightly different.
With chocolate (and caffeine), it’s not only that, pound for pound, a dog is more likely to overeat than a human, that is a minor point, but the fact that dogs (and cats) use a slightly different pathway to clear the offending family of substances (theobromines). Humans are much better at the pathway called glucourodination than dogs, and dogs are slightly better than cats. These affect everything that uses that pathway, including some drugs. Because humans are more efficient at using this pathway, the concentration of theobromine accumulates at a higher rate in dogs and cats. The lethal dose for cats and chocolate is even smaller than for dogs, but they tend to eat chocolate waaaay less than dogs.
For onions and their families, you have the same issue as above, plus (IIR my clin path correctly), the cell membranes of their erythrocytes have slightly different chemical composition, which is more affected once more by the compounds present in the onion family. So onion (and related) can cause anemia by destroying the red blood cells.
For dairy products it is the same as lactose intolerant humans, in that they lack lactase as adults.
For some compounds, they don’t have a clear reason yet why they’re toxic other than “they are”.
Regarding the “food that belongs to cat” joke, for cats, eating dog food (that is, the food that is marketed specifically for dogs, be it canned or dry) IS lethal.
Cats have an absolute requirement for taurine, an amino acid that is not essential for dogs. Being more obligate carnivores than dogs, they would get this from their usual hunting. But if they’re fed dog food because, say, there’s a dog in the house and is cheaper to buy one brand than two separate ones, they’ll get serious health problems. They can get blind because of lack of taurine, as well as develop a heart condition called dilated cardiomyopathy (natch, this is congenital in dogs and cows).
Careful with that pet theory:
http://www.petmd.com/blogs/thedailyvet/jlee/2012/may/salt_water_poisonous_to_dogs-20569
Interesting. Thank you. Now if only I could get my dog to read it…
But that’s not so much that the food itself is dangerous, just that it’s inadequate. If humans eat nothing but biscuits and salt pork, we’ll get very sick or die from scurvy… but that doesn’t mean that biscuits or salt pork are themselves bad, just that you need something else with them. Would a cat be seriously harmed by dog food (beyond presumed digestive distress from excessive carbs) if it also had access to a good supply of taurine?
You’re correct in that by itself it’s not lethal, and would be more equivalent to the different types of malnutrition suffered by humans due to lack of vitamins.
I just brought it up because of the joke mentioned before “hey, eating the cat’s food is dangerous for the dog (because the cat will attack)”. 
Dogs have brains? Mine still haven’t figured out there’s a cat living in the crawl space.
You can get your cats to eat dog food, or is that just a hypothetical case? Mine all turned up their noses at dog food like it was poisonous AND were insulted that I thought they might eat it.
No, it was real. It was also the case with correctly labelled taurine-less cat food before they realized the cats needed taurine. But the recorded cases come from both sources of taurine-less diets.
I don’t think that, technically speaking, there are foods dogs can eat that people can’t, that are equivalent to the raisins, chocolate, pistachios, and xylitol that are digestible by humans, but quite toxic to dogs.
But dogs are adapted to digesting carrion, and people aren’t. Salmonella, for example, is fairly well dealt with by dogs, but not by humans. A goodly percentage of commercial dog food recalls are because of salmonella, which is likely to make people sick but not dogs.