[saiya-jin]

Correlation != causation. India is mostly vegetarian, not vegan - people eat diary products like paneer, ghee and yoghurt en masse. Meat foods are generally not that great - chicken with tons of bones, very chewy mutton, fish with tons of thin bones. I became +-vegetarian for few months when I backpacked there.

Their diet is generally not that good though - tons of carbs, little physical activity unless in 'blue collar' job. Older folks are almost always overweight. Maybe genes also don't help, not sure there.