And lead to a myriad of other problems unless the whole grains come from a wide variety of sources, are either non-processed or fermented and are non genetically modified.
Most people get almost all of their grains from three sources: corn, wheat and soy, which also happen to be the three most genetically modified crops on the planet. They would love to have you believe that a diet high in grains is a healthy one.
The healthiest diet is one close to what our ancestors evolved (or adapted) to eat over 10,000 years ago - and there weren't a great deal of grains in it.
Before you buy into the latest mainstream "advice", do Google search on "dangers of eating grains" and take a look at some of the articles that turn up.