When science is diluted... or just wrong

If you live in Australia you will know that for the last 20 years it has been a crime or at least a horrific sin againt society, health and right thinking to be outdoors for any length of time without being covered head to foot in 30+ sunscreen and a hat - and that's just at nighttime!
We have been told to wear sunscreen every day regardless of sunshine or temperature, and to avoid being in the sun between 11 and 3. (That puts rather a dampener on most summertime activities.  On the other hand it's a good excuse to stay inside days over 35 degrees if you are heat intolerant like me).
Earnest advice from most quarters has been advising for so long that the sun is unhealthy and dangerous, that most of the extreme advice above has been accepted more or less without question.
But the truth is rarely at the extremes. (I had written "never" but that's an extreme...)

Now it turns out that Australia is experiencing an increase in cases of rickets, with a University of Melbourne study finding significant numbers of people in its study to be vitamin D deficient, and the Paediatric Surveillance Unit finding nearly 1300 Australian children under 15 develop rickets each year.
Rickets.
In a first world country, in the twenty-first century.
Rickets!
Because, it seems, people have taken to heart the very strong, long-standing, scary and persistent advice to stay out of the sun, to the point where they or their children are not getting enough vitamin D.

Yes we know that Australia has one of the highest rates of skin cancer in the world, and no one wants to go back to the days when I was a kid, when we would all get so sunburnt every summer it was a regular evening activity to peel each others' skin off our backs, and you'd graduate each summer with a few more freckles and a redder nose than last year. But why do we go from one extreme to the other?
Why does the general wisdom on what's healthy and what's not seem to do back-flips and see-saws between different positions, when logic would say that a middle ground must be best?

We know that scientific findings are always being challenged and extended, modified, or overturned, but in the areas of health and well-being the changes are dizzying. Usually the blame is laid with the media for watering down or sensationalising scientific findings, or science outfits after funding publicising their work prematurely or following a popular angle. These things are a factor. Is there something more?
For some reason we don't seem to be able to get a handle on the most basic aspects of what's good for us and how much of things we need (such as sunshine).

Weight and nutrition are other ones. How much meat should you eat? How much dairy? Should you eat dairy at all? I remember a comedian years ago saying "Here is a question you cannot answer. Milk: good or bad?" It was funny. It was true. Years later we still cannot answer it, officially. But unofficially, inside most people's heads, the answer is obvious: good, in moderation.

Here are some other bits of common wisdom, all derived from valid scientific studies, where some part of the finding has been stripped out and repeated for years until it has become something most of us accept as truth - until the next study, some time in the next 2-10 years, flips it on its head.

Drink at least two litres of water a day and more in summer.
Thirst often masquarades as hunger; if you think you feel hungry you may actually be thirsty.
Obesity leads to cancer, heart disease and diabetes and is a huge cost on the health system.
Raw food is better for you than cooked food [and yet humans have been cooking food for millenia].
Organic vegetables are better than intensively farmed vegetables [and you know what, they probably are. But seriously with 7 billion people, what are we going to do].
A glass of red wine a day promotes longevity.
Blueberries, broccoli and others are superfoods which contain antioxidants which cleanse the body and flush out toxins.
A Mars a day helps you work rest and play. Just kidding - that one did not come from a scientific study. But it was acceptable as an advertising jingle for a long time, hard as that is to believe now.

I have just realised everything I have listed here pertains to nutrition.
One of the key obsessions of our time, and one of the worst areas for yo-yoing advice in pop science.
Much of the stuff we read or are told is from preliminary or incomplete studies and confuses correlation with causation.
Here is a good example.
For some time now it has been said that being overweight hinders women from falling pregnant, and the reason was possibly something to do with the way fat cells interfered with hormones.
Then another study was done, and this time it seemed people spoke to the women or observed their behaviour. Turns out the reason for lower pregnancy rates is actually that overweight women are self-conscious about their bodies and have sex less often.
Like, DER.
How often do you read these "latest findings" and feel angry? How often do you feel cynicism, or fear, or depression or despair? Do you think "Not this old thing again" or "Wow, that doesn't sound right, but I guess those guys know...". Or do you think "Oh no! How will I fit this one in too?" or "Bloody hell, what are we meant to be doing this year then?" Or do you let it all pass over your head and just get on with your life? (Easier said than done).

As the classic - and perenially true - wisdom says: Moderation in all things.