Vitamin B12 is one thing that many vegetarians do not have enough of. You can eat good food every day. You can feel full. But your body can still be empty on B12. This is very common in India because so many of us do not eat meat or eggs for years.
I will tell you what happens when your body runs low on B12. These are real signs. You can see them in yourself or in your signs of vitamin b12 deficiency in vegetarians.