>He regularly gives advice to people who have risk factors like high blood pressure or high cholesterol, but the advice he gives them (eat in moderation, eat more vegetables and less junk food, exercise a little) is pretty generic, and none of them follow it anyway.
Doesn't that kind of justify his ignorance, though? Doctors don't have time to be experts on everything (or on anything, really), and it seems unlikely that an ability to hold informed discourse on the nutritional value of broccoli would have anything more than a marginal effect on outcomes for his patients.
All it means is that patients who are interested in nutrition don't discuss it with their doctors. I think the people who actually ask him for advice on nutrition tend to be older, poorly educated, and very dependent on authority. Everybody else takes it for granted that doctors don't have any useful information on living a healthy life. A doctor is just somebody who diagnoses and prescribes. My friend got his head stuffed chock full of arcane knowledge in medical school, and he gets a torrent of "education" from drug companies, but when it comes to the effect of lifestyle on health, he's less educated than most of my yuppie friends.
This is a waste, because the people who are in the best position to understand and evaluate information about living a healthy lifestyle have no influence on the production or consumption of this information, except when they themselves get in on the business.
He could do better, though, not just with nutrition but with other lifestyle factors. For instance, he could explain to older women that doing weight-bearing exercise will reduce their risk of osteoporosis, and he could tell them how to get calcium if they have problems with dairy products.
But my point was that very few people even bother asking him for guidance. It's silly that educated people just assume that by reading a little in their spare time they can acquire a better practical knowledge of nutrition than a professional with four or more years of intense training in human medicine. It's mind-boggling that they're right. For instance, if my friend could name a couple of high-calcium non-dairy foods -- which I'm not confident he could -- it's only because he read some diet books looking for ways to lose weight. He could probably name more symptoms of Chagas disease than dietary sources of vitamin D.
Doesn't that kind of justify his ignorance, though? Doctors don't have time to be experts on everything (or on anything, really), and it seems unlikely that an ability to hold informed discourse on the nutritional value of broccoli would have anything more than a marginal effect on outcomes for his patients.