For those who having beta thalassemia, what food should they eat and what should not they eat?

Major or minor? Beta thal minor is a non-problem; the rate of red cell production is somewhat higher so get plenty of Folic Acid in your diet or supplement. Beta thal major is a very serious illness requiring lifelong close management by a physician; again, the need for Folic Acid and a generally nutritious diet is worth remembering but there's no magical food remedy. Good luck.