Humans are meant to eat meat, not just veggies.
For starters, the small intestine of carnivores is much shorter than non-carnivores and has a higher level of acidity in the stomach. This is because the nutrients need to be extracted and the waste expelled before the meat rots inside the body(which it partially does in a human body since our intestine is much longer by comparison than other carnivores).
There's also the issue of short, dull, canines and much smaller temporalis muscle that powers the jaw. This is why we have to spend more time chewing and grinding meat down into smaller pieces instead of just tearing off chunks and swallowing it whole like most carnivores. We wouldn't be able very easily bite through hide and tear chunks of meat off nor would we be able to digest (most)raw meat without getting sick.
Most of our carnivorous traits are remnants from evolution that were never replaced. We more closely resemble a herbivore that has maintained some basic primal ability to process meat than we do a carnivore that has adapted to process vegetation.
"Like the hard-core carnivores, we have fairly simple digestive systems well suited to the consumption of animal protein, which breaks down quickly. Contrary to what your magazine article says, the human small intestine, at 23 feet, is a little under eight times body length (assuming a mouth-to-anus "body length" of three feet). This is about midway between cats (three times body length), dogs (3-1/2 times), and other well-known meat eaters on the one hand and plant eaters such as cattle (20 to 1) and horses (12 to 1) on the other. This tends to support the idea that we are omnivores.
Herbivores also have a variety of specialized digestive organs capable of breaking down cellulose, the main component of plant tissue. Humans find cellulose totally indigestible, and even plant eaters have to take their time with it. If you were a ruminant (cud eater), for instance, you might have a stomach with four compartments, enabling you to cough up last night's alfalfa and chew on it all over again.
Or you might have an enlarged cecum, a sac attached to the intestines, where rabbits and such store food until their intestinal bacteria have time to do their stuff. Digestion in such cases takes place by a process of fermentation — bacteria actually "eat" the cellulose and the host animal consumes what results, namely bacteria dung.
The story is roughly the same with teeth. We're equipped with an all-purpose set of ivories equally suited to liver and onions."
http://www.straightdope.com/columns/read/674/are-humans-meat...
But I really don't know why you added "heavily spiced" in there. Spices are usually more or less nutritionally neutral.
Nutritionally neutral, but not gastrointestinally, as folks sensitive to spicy food can attest.
And what's wrong with taking supplements? You keep invoking the concept of "natural", but there is nothing intrinsically superior about nature. Humans are in control now, and we're doing a lot better for ourselves than nature ever did.
I'm not a vegetarian, because I love my meat, but if you can give me a meat replacement that's indistinguishable in nutrition, texture, and flavour, what's wrong with that?