I have no firsthand knowledge of Indian home cooking, but here's an article about it which claims it's common. https://www.seriouseats.com/2020/02/mustard-oil-

I have no firsthand knowledge of Indian home cooking, but here's an article about it which claims it's common. https://www.seriouseats.com/2020/02/mustard-oil-guide.html https://www.seriouseats.com/2020/02/mustard-oil-guide.html From what I've seen in passing most people attribute rising heart disease to economic prosperity leading to a more westernised diet but I haven't really looked into it.