From Mead on The Greening of Godzilla:
...on issues the public follows closely, the scientific consensus keeps changing. Margarine was introduced as the healthy alternative to butter; now experts tell us that the transfats in many types of margarine are the worst things you can eat. Should you eat no fat or the right fat? All carbs, no carbs or good carbs? How much vitamin E should you take? How much sun should you get? How much fish oil should you swallow? How should you divide your time between aerobic and non-aerobic exercise? On these and many other subjects, expert opinion keeps changing. Perhaps the current consensus will last; quite possibly, it won’t — but the experts can’t tell you what will happen.
Nobody trusts experts to be right, except those with no scientific education at all. Furthermore, real experts are humble about things.