It’s so unnatural that I increased my benchpress by nearly 40 lbs, was able to do a dip where for the first time in my life, I had to ADD weight to my body rather than be assisted, and where I had enough energy to do those exercises after an hour of taekwondo class. And after I did all of those exercises, I went ice skating. Oh, by the way, I rode my bicycle to taekwondo practice. Gee, when I still ate meat, I couldn’t do half of that. I wonder why?
Veganism is totally unnatural for our species. Our line has been omnivorous for millions of years, while the other hominids that were vegetarians became extinct (perhaps there's a lesson there for you). Another tip-off for its unnaturalness is that it's impossible to get enough vitamin B-12 without supplementation eating a vegan diet.
And further, following your "logic," why is it ok for you to kill plants? They're certainly living, aren't they? How do we know that tomato you're slicing doesn't feel pain? Just because it doesn't scream?
Perhaps you should just eat dirt.