Humans can only synthesize a small amount of glucose from proteins via gluconeogenesis, and at the cost of the production of ketones which increases blood acidity and stresses the liver and kidneys. You couldn’t live on pure protein and lipids, and you most certainly do need to consume carbohydrates. However, vertebrate muscle tissue is at most 30% protein, and some types of organ meats are upwards of 60% carbohydrates. Most members of order Carnivora are not strict carnivores; the few that are are apex predators which do not engage in extended aerobic pursuit but instead rely on stealth and stalking predation to achieve kills, limiting the need for raw carbohydrate consumption.
Well, the Master disagrees, one can exist safely on a all-meat diet:
Most meat contains 0 carbs. It’s true, as you say that meat isn’t all proteins, it does contain a significant amount of water, and of course fat. Some does contain a tiny amount of carbs.
"Adult mammalian muscle flesh consists of roughly 75 percent of water, 19 percent of protein, 2.5 percent of intramuscular fat, 1.2 percent of carbohydrates and 2.3 percent of other soluble non-protein substances. These include nitrogenous compounds, such as amino acids, and inorganic substances such as minerals.[35]
Yeah,** Stranger**, I’m afraid I want cites about the need for carbohydrates (and about significant carbs being present in animals). An all-protein diet can lead to starvation (‘rabbit starvation’), but as far as I know, fats can easily provide enough calories with no carbs at all in the diet. There are many, many examples of humans living for years in Arctic or Antarctic conditions subsisting entirely on animal products.
I understand for some of them the lack of fiber led to constipation, but not life-threatening conditions. So I think fiber is more in the ‘optional’ category than ‘required’. (as opposed to vitamins and other trace minerals which you don’t need much of, but definitely do need).
Look at those animal shows and you can see the lions and hyenas and other animals go straight for the organ meats first including the gut. If a lion eats the stomach he’s also eating grass and whatever else the prey has eaten.
Animals aren’t horribly fussy. A cow in a field basically grazes and puts everything in his mouth. He will swallow it and he learns “that made me sick, don’t eat that.” Otherwise he will. Then he learns to put stuff in his mouth and spit out what he shouldn’t eat.
Most animals at some stage, especially as babies, eat bugs which are full of protein. Even hummingbirds which are nectar machines eat tiny bugs.
If you look at digestive systems of cows they take a long time to digest their food. This is because the food has to stay in the cow a long time so, the cow can extract all the vitimins and nutrients in it. If a human eats the same food, it shoots through them so fast there is no time for the human body to extract the nutrition.
When we send food to starving countries, we don’t send them fresh veggies and a variety of food stuffs. We simply send them a mash of soy and oatmeal and other protein rich foods. You can easily live on the same food day in and day out. It’s monotomous but fully do-able.
“The cow…HE will eat”? What is this, a cock and cow story?
In response to the general question, mammalian carnivore families vary widely in how exclusively carnivorous they are. Some kinds of bears are almost entirely vegetarian (pandas for instance, now again generally considered to be in the bear family after years of being exiled among the raccoons). Most other bears seek berries and other vegetable foods in season, and the greed for honey is factual. Moving on to dogs, I never met a dog that didn’t love sweets, like one that we had for years who demanded TicTacs whenever we had them. He needed them too. Cats are the most carnivorous, and they are not horribly fussy either. I had always wondered how a cat goes about actually eating a mouse. I’d assumed it first makes some effort to dress it out, as it were, by removing the skin and fur to reveal the choice parts. But no. Having had the opportunity to watch some YouTube clips, that isn’t what happens; instead, they generally chomp down on the whole thing from one end to the other, as you or I would eat a Danish! This is so utterly unlike the cans of Medley that my three boys yip and mewp and pester me for!