"The number one thing one can do to improve his or her overall health and fitness is to GIVE UP GRAINS.
Why?
They are a distinctly Neolithic food that humans have yet to adapt to consuming, they contain anti-nutrients (lectins, gluten, phytates) that are unhealthy and should be avoided, insoluble grain fiber (often touted as necessary for gastrointestinal tract health) is non-essential, there are better sources of vitamins and minerals (see meat, healthy fats and vegetables), and they are carb-dense.
All-in-all they are completely and utterly pointless in the context of a healthy diet; nothing but a cheap source of calories." - Mark Sisson, blogger, speaker, and author