Are Grains to Blame?
Will cutting out grains make you healthier? It depends. Nutrition Diva dives into the great grains debate.
Q. "I understand that grains are not necessarily nutrient-dense or even necessary, but can they be a cause of health/behavioral/psychological problems (beyond celiac disease)? Is it true that gluten acts like an opiate in our brains and that we can become addicted to grains? Is there merit to the claim that eliminating grains can cure lots of health problems?"
A. It is true that gluten can be broken down during digestion into peptides (strings of amino acids) that can stimulate opiate receptors in the brain. Hypothetically, the stimulation of those opiate receptors could produce euphoric effects and subsequent cravings for more of the same. Perhaps some people are especially sensitive to this effect. That's about as far down that road as I'm willing to travel, given the scarcity of hard data.
Will Eliminating Grains Solve Your Health Problems?
As for whether eliminating grains can cure lots of health problems, a lot depends on
1) what else gets eliminated along with them, and
2) what you replace it with.
(You can substitute any other food, food group, or ingredient for the word "grains" in the previous statement, by the way.)
For example, a lot of grain-based foods are also high in sugar. If avoiding grains also means you're eating a lot less sugar, that could certainly improve your health, but might not have anything to do with gluten. Similarly, are you replacing your dinner roll with a salad or with French fries? How can you tell which effects are from eliminating gluten and which are from eating more vegetables (or more French fries).
You could always try avoiding grains and seeing if you feel better. If you do, it doesn't really matter whether it's truly because of the lack of gluten in your diet or because of other factors, right? But I think the claim that "eliminating grains can cure lots of health problems" is far too broad to be taken seriously.