I am always struck by how difficult it is for people to see how much cruelty they are bringing not only upon animals but upon themselves and their loved ones and other people, how much we are screwing up the planet, how much we are hurting our own health, how hard it is to change all that, how eager people are to make a buck at everybody else's expense - all those things are discouraging.

I think herd mentality is a good thing overall. Because if every sheep had to figure out the velocity of the wolf and their personal risk, that would take forever.

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.

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

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.

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.

People have to know that if they've wanted to lose weight, if they've wanted to get their diabetes better and get their cholesterol down, here is how it works. Beyond that point, you can't force people into changes, you have to guide them.