As for healthy people's recommendations, I sometimes think they believe they're well because they did something right, and people who are ill did something wrong lifestyle-wise, or are doing something wrong now. Hence we need their not-so-expert opinions to get better, or something!
In the US we are taught from birth to obey without question. If one obeys, one will be rewarded. Disobedience will also be rewarded, but with suffering. Therefore, if we are suffering with illness, well obviously it's because we failed to obey: "I'm a good person. I followed all the rules. So why did something bad happen to me? I must not be good enough to be well."
Even eating is a moral act: "I really want a chocolate, but chocolate is bad, therefore if I eat it, that makes me bad."
It's all about controlling people, and putting them into their "proper" place in the social hierarchy. People who are sick, old, and poor, well, we are pretty much at the bottom. Everyone else wants to keep us on the bottom so they can feel better about themselves. Ugh. Stop the world: I want to get off. This amusement park isn't amusing anymore.