I think we have to do everything that's useful. We're doctors. Our job is to tell the truth. And it doesn't have to be embellished in any way.

In my own life, I decided to leave meat off my plate in medical school, but was a bit slow to realise that dairy products and eggs are not health foods either.

Chimpanzees will eat a little bit of meat. But, they never eat dairy products, and no other animal would do that.

I'm thinking of people in rural Japan and China, where McDonald's hasn't yet arrived. These are the thinnest, healthiest, longest-lived people with the least risk of cardiovascular disease and diabetes.

The important thing is that while heroin and cocaine and tobacco and every drug and junk food cause dopamine release, there are healthier ways that you can put this into your life. And the three big ones are intimacy ... physical activity ... and the third thing is music.

I was aware of what animals go through because I had driven animals to slaughter and I'd killed animals. And I was aware that there were certain ethical issues, but they weren't preying on my mind very heavily.

While it's certainly true that many people think that dairy doesn't have a cost to the animal, it's because they never went to a dairy farm.