Lately I and others I know have, on dentist’s visits, gotten a fair amount of lecturing about excessively forceful brushing, ensuring the brush/bristles are soft, avoiding gumline erosion, etc. Fine, it sounds sensible to me – but when I queried the dentist as to when this emphasis on protecting the gums had come in, and when hard bristled brushes had gone out of favor, he assured me this had always been the rule. Now, I could be imagining things, but I seem to remember more than a little past emphasis on brushing firmly, stimulating the gums, making sure the disclosing tablet didn’t show you missing a spot – and little or no talk about the concept of brushing “too hard.” Why did they <ever> sell/make anything but soft-bristle brushes if giving the teeth a good forceful polishing weren’t, at some point, viewed as desirable? What I’m pretty sure has happened is that periodontal thinking has changed a bit (as medical thinking often does), and they’ve come to realize that after 40-50 years of increasing oral hygiene, people may have gone overboard a bit on attacking the plaque, so now they emphasize “gentle” brushing. Fine; but why deny that the rules have changed?
You see this with the fat vs. carbohydrate debate: The anti-Atkins crowd will frequently say something along the lines of “Naturally, we’ve always told you that it was desirable to eat plenty of <good> fats like salmon/nuts/avocados; all we ever warned you against was the bad evil saturated fats.” I <know> that is not an accurate portrayal of the “fat is bad” message as promulgated over the years; I know any number of people who have been dieting more or less nonstop since the '70s or '80s can’t look at guacamole or peanuts, or even olive oil on salad, without fear of putting on poundage. Why not just <admit> that the anti-fat message was oversimplified before, but the new version is more nuanced and scientifically correct – if that’s what its proponents believe?
I also seem to remember some simple computational error or fallacious assumption that led to our being assured for years that shellfish were high in cholesterol and to be avoided on these grounds – but I don’t remember anyone in the med./nutrition industry admitting that the data/advice had been just plain wrong.
Any other examples in which “X is good/bad for your health” has been significantly revised and the health professionals take the “Nothing to see here, move along” approach? Thoughts on why this tendency seems to exist?