It is true that heirloom varieties are significantly better options in general. The fact that humans are so reckless and out of tune with the biology of our world does not mean that veganism should be avoided. Being in balance means largely disposing of our 'advanced technological' approach to food production.

I can show you many vegans who do not have dental problems who have been vegan for much loner than me. My teeth are not perfect by any means but then they never have been, both before and after becoming vegan. Without restorative dentistry my mouth would be a bit of a mess. I put this down, in part, to living in Britain where it is literally impossible for me to get enough sunlight to ensure the correct functioning of some of the processes in my body. Again, living naturally - out doors - would go a long way to helping this, but in Britain and perhaps in New Zealand (I'm not sure) it still wouldn't be enough. Our planet is hugely out of balance (including it's axial tilt) and so we have a lot working against us.