|Barked: Fri Nov 4, '11 2:11am PST |
|scientifically speaking, raw is far easier to digest than cooked.
Humans have a longer GI tract, which makes it easier for bacteria like e.coli, salmonella and staph to breed, and these sorts of bacteria cannot breed quickly in a short GI tract like dogs and cats have. think about it. Dogs can't cook their own food. Dogs are natural scavengers and hunters of small animals. They are descended from Arabian wolves, so in the wild their natural prey is goat sized and smaller as well as whatever carrion, fruits, and root veggies they can scrounge. They are pretty firmly in the southern branch of grey wolves, although spitzes are an exception, being a blend of northern wolf and southern.
What this means, and it makes sense, is that they are pretty good at handling cooked food because they would be suited to eating sun-baked carrion. They would encounter stuff that was just a dose of salt short of jerky on a regular basis. Conservation of energy would dictate that carrion is easier to come across and eat than chasing down live prey.
Then humans come along, and they have been eating cooked meat for a while. Cooked meat is easier for humans to eat because our digestive systems are hybrid. One current theory is that we were all originally fruit and nut eaters, and then at a critical point in hominid history, there was a severe global drought that almost wiped out our species and we learned to survive by eating fish and shellfish exclusively. After that, and used to protein in the diet, we became hunters and became almost exclusively predatory for a while, before the advent of farming and settlement at which point we became more balanced in our diet between plants and animals. What this leaves on our structure is a body that is suited to eating fruits, nuts, and tender leaves and shoots, but a society that values and understands the need for meat as a quick and useful source of energy.
Proteins are naturally elastic. think about a muscle. it has to expand and contract while maintaining its basic structure. Cooking animal protein stiffens that elasticity so that it can no longer do that. It changes the structure of the protein to a form that is not bioavailable. What our body does with cooked meat is it has to sort through all of the cooked and denatured protein in the cooked food to find that small amount that is still intact before it moves its way out of the intestine.
In other words, cooking slows down our body's ability to readily access usable protein. This is important to humans because our intestines are meant to handle tender leaves, tender shoots, fruits, seeds, and maybe insects. By slowing down the bioavailability of protein, cooking meat simulates the bioavailability of protein in fruit, seeds, and tender vegetables.
Plants present a different problem. the same protein that is in animals is also in plants. the problem is that the protein is essentially trapped by cellulose, complex carbs, and a polymer of fructose called insoluble fiber. Herbivores have long guts and/or bacterial flora that can break down this stuff. Omnivorous humans and carnivorous dogs do not have this. Omnivorous humans have salivary amylaze, an enzyme that can break down starch. Dogs have amylase too, but farther down in the digestive process. Humans have boxy teeth to facilitate the grinding of tough substances, dogs have teeth designed to shear muscle and break bone. Humans and dogs both benefit from cooked vegetables because for humans and dogs it breaks down the tough fibers that we can't digest, for dogs, they need the vegetable and fruit matter to be almost pulped before they can benefit from the proteins and the vitamins that are in them. Unfortunately, that very process of freeing the proteins for bioavailability through cooking the vegetables destroys the very nutrients we are trying to free. Humans don't need to have their vegetables quite that cooked. Our gut like a happy medium, broken down just enough so that they are tender. For dogs, it's probably better to just pass unless it's a special treat. certain veggies like carrots taste sweet and all mammals except cats are programmed to crave salt, fat, and sweet. Only Cats as a taxonomic family can't taste sweetness, so they are a slight exception. Dogs can taste sweetness, so they are no exception.
So back to the evolution story; humans come along and meet up with wolves, already knowing how to cook these proteins. funny how cooked proteins are similar to sun-baked carrion. It is good for the wolf, and it feeds him well. Sun-baked carrion would have been a staple of the arabian wolf diet. To such a wolf, the raw protein works better, but it takes a lot of energy to chase raw food down in the heat of the desert. Fortunately by co-opting humans, they can can get fresh food on demand. Suddenly both raw food and sun-baked/cooked food costs the same energy to acquire.
So, following conservation of energy, the highest value(in terms of protein, fat, salt, sugar, other nutrients) food it can digest for the smallest amount of energy is the preferable diet for the animal. In the case of dogs, their diet being split between high-value, high energy live prey and medium value low energy sun-baked carrion, on it's own the carrion is a more efficient option. When humans can hunt for them and drag back fresh carcasses, the raw meat will always be preferred, and both will be preferred to vegetables, no matter how well cooked.
Long story short, cooking makes food simulate the tender shoots and fruits that humans are built to eat, cooking food simulates the sun-baked carrion that arabian wolves eat as a staple, but not as a preferred source. Dogs, as descendants of those wolves can gladly eat cooked protein their whole lives, but raw is preferable, while humans can eat cooked meat all of their lives, but tender veggies, fruits and nuts are actually preferable as far as our guts are concerned.
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