> The article mentions Gandhi. Many in India have been vegetarian for millennia, including many Brahmin. It seems to have worked for them over the past 3000 years.

There's a lot of B12 deficiency in India, for example:

> Conclusion: Prevalence of vitamin B12 deficiency is 47% in north Indian population. People with diabetes have higher vitamin B12 levels than general population though still have high prevalence of deficiency. This data shows that Vitamin B12 deficiency is widespread in Indian population.

https://www.ijem.in/article.asp?issn=2230-8210;year=2019;vol...

The study is mentioned in the article.