How To Avoid Hair From Getting Grey?

I'm a 26 year old woman but I'm already getting white hair along my temples. I also suffer from dandruff which results in hair fall. I shampoo every 2 days and use 2 shampoos - Head and Shoulders for dandruff and Dove for hair fall. I also use a Loreal Conditioner and oil my hair once a week with olive oil. Please tell me how can I get rid of these problems. I don't want to color my hair. Is there a capsule I can take to fight greying?