This time it is fiber, which contrary to the collective wisdom of the brightest minds in medicine apparently does not ward off colon cancer after all. Over and over, the conventional medical wisdom collapses under the weight of new evidence. Now it is pretty clear that salt is not an important cause of high blood pressure.
Most people probably can eat an egg for breakfast without triggering a heart attack.
No one really knows how that will turn out, but there is doubt about the long-accepted assumption that it keeps the heart working smoothly after menopause. It may have been the best guess at the moment. But often the recommendations are repeated so many times that people forget they were rough guesses in the first place and come to think they are hard facts. This is not to say everything is wrong or likely to be overturned tomorrow. For instance, scientists feel absolutely certain that smoking is bad.