I've never much agreed with the bipolar-style flip-flopping between extremes that comes with dietary guidelines, studies, and conventional widsom.
Take for instance salt—or sodium, in the physiological sense. An article published today in The New York Times, written by Aaron E. Carroll, called Dash of Salt Does No Harm. Extremes Are the Enemy:
For years, we have known that diets high in salt can be bad for people with high blood pressure.
Except, maybe not:
Why? There’s surprisingly little rationale for this belief. Last year, experts convened by the Institute of Medicine assessed the evidence concerning sodium intake around the world. They agreed that efforts to reduce excessive sodium were warranted. But they cautioned that no such evidence existed to recommend a very low salt diet.
By the end of the article, Carroll's discussion topic has changed:
Why experts and organizations feel the need to go from one extreme to the other is unclear. But it’s unfortunately something we do far too often in medicine.
Regarding salt: generally, I'm not afraid of it. As we've seen, a diet way too high in sodium can produce blood pressure issues, although this is mainly seen in people who already have blood pressure issues. Furthermore, we now know that diets that are too low in sodium actually seem riskier than the too-high diets.
As a science-minded individual, I'm critical of epidemiological ("observational") studies by default. Simply following a population over a time period and making generalizations about relationships is a dangerous and ill-informed practice, especially when we consider how the media and population reacts when they hear the results. We always tend to flip-flop to the opposite end of the extreme, to even more dangerous results.
(Continuing on the salt train for a moment more: salt intake needs to be highly individualized. People who eat a lot of cooked food generally require more salt for enzyme production. Athletes demand a higher intake of sodium, for both electrolyte purposes and to keep up with the metabolic demands of a high-protein diet.)
We've seen this flip-flopping with everything. I'm notorious for pushing a diet higher in fats, despite what the American Heart Association has to say on the matter. This is primarily because government organizations are notorious for being slow to adapt to advances in scientific understanding, and it would be unwise to blindly follow the recommendations of those who aren't doing the research themselves. Those who are doing the research are shouting something completely different:
But later research showed us that egg consumption had no relationship to cardiovascular disease for most people. In fact, a majority of people’s serum cholesterol level has little to do with how much cholesterol is in their diet.
(In case you missed it: the above paragraph contains links to four peer-reviewed studies.)
All this being said, I've also never much agreed with the popular saying "everything in moderation". The very concept of “moderation” is intangible—so fluffy as to be meaningless. These days, there's an understood level of optimal that we should all strive to achieve. Instead of eating too much or too little of anything, and instead of finding some arbitrary middle ground, we should all do our own research, find what works best for us, and follow that path for as long as it works.
Perhaps the real takeaway is this: take everything you hear regarding your health with a grain of salt.