Looks like Michael Mosley's "Trust me I'm a doctor" series is looking at veganism.
bbc.co.uk/news/health-45409471
His summary:
"The researchers found being a vegetarian or vegan was associated with a significantly lower risk of heart disease and cancer, though there was no difference in all-cause mortality.
In other words, being a vegetarian or vegan was associated with being healthier but not necessarily with living longer. "