I think that diets, and particular foods, also have a placebo effect (as well as a nocebo effect - if we believe they are doing us harm, they will). People who swear by a daily bowl of blueberries, salmon three times a week, only raw dairy products ... or raw diets, low-carb diets, vegan diets ... are benefiting, in part, by the strength of their belief. Not that there's anything wrong with that. In fact, it would be great if we could tap into this innate healing ability at will.
What's your food placebo? One of mine is kabocha squash. In lieu of that, sweet potatoes. Sweet potato withdraw is nasty. I think I know what Ronald's is.