When a typical westerner goes to the doctor with a headache, we expect a prescription for a pill or shot or liquid that will “attack” the headache. We probably would not go back if the doctor massaged our feet or stuck needles in random body parts or told us to give up meat, eggs, milk, cheese, and processed foods to make the headache go away. The truth, however, is that any of these treatments could be more effective than pills, shots, or liquids because the head is connected to the rest of the body.
A body is a whole thing with many inter-related parts. Isolating a brain or a pancreas or a heart or a blood vessel may be helpful for scientists trying to understand how they work, but all the parts work together in awesome ways to keep the body going, slow it down, or kill it. Even when it malfunctions and fails, a body is awesome. It knows what to do, and has a lot of alternative strategies, but when the substances it is given are conflicting and chaotic, it will eventually fail.
This interconnected human body is not built to be nourished by the flesh, eggs, or milk of other animals. How we became omnivores that have survived eating all kinds of things is a fascinating anthropological and biological story, but it’s a whole other long story. Our ability to adapt to adverse environments has given us shorter lives filled with more pain than necessary.