We can avoid vitamin B12 deficiency diseases if we include good nutrients and proper B12-rich foods in our diet

Egg is the top source in this list. 

For non vegetarian people there are food such as – meat, chicken, fish rich in vitamin b12. 

Green vegies such as Broccoli, spinach are the most important sources of vitamin b12

Peanuts are also considered as best food that should be eaten by people who are suffering from Vitamin b12 deficiency

Mushrooms and Lima beans can be included in one's diet to overcome with deficiency of Vit-b12

Fruits are healthy in so many other ways, some of them are top choice for vit-b12 such as Oranges, bananas, lemons, strawberries etc

All the dairy product food items are rich in Vitamin B12 such as milk, cheese, yogurt, curd etc.