"Settled science" and BuzzFeed share a fatal commonality.  Both are driven by an agenda rather than facts.  BuzzFeed learned that lesson yet another time last week.  Two years ago, the publication pushed the Clinton-bought phony and unverified Trump Russia dossier, which launched stories of collusion, FISA warrants, and the ongoing Mueller investigation.

In a bit of irony, it was the Mueller team that slapped down BuzzFeed's latest story accusing President Trump of asking Michael Cohen to lie to Congress.  Imagine the fake news media being fact-checked by their hero, Robert Mueller.

So-called settled science faces similar collisions with reality.  Driven by a particular agenda, whether financial or political, science becomes blinded to any contrarian views, insisting that the issue is "settled," shutting off any further inquiry, debate, or honest disagreement.  In some areas of science, dissenters are labeled as "deniers" with threats of violence, loss of job, or even imprisonment.

The most prevalent example is climate.  From global cooling in the 1970s to global warming in the 2000s, the names have changed, but not the agenda.  Since climate models are misbehaving, not providing the desired predictions, the names have morphed into "climate change" or "extreme weather."  But still the science is considered "settled."

Barack Obama in 2014 told Congress, "The debate is settled, climate change is a fact."

Someone with a bit more science knowledge than the community organizer from Chicago, physician and author Michael Crichton, said this about settled science: "There is no such thing as consensus science.  If it's consensus, it isn't science.  If it's science, it isn't consensus.  Period."

The latest bit of unsettled science is something few of us are thinking about in the midst of global warming-induced winter storms and piles of snow – namely, sunscreen.

A recent article in Outside magazine sums it up: "Current guidelines for sun exposure are unhealthy and unscientific, controversial new research suggests – and quite possibly even racist.  How did we get it so wrong?"

It started with vitamin D.

People with low levels of vitamin D in their blood have significantly higher rates of virtually every disease and disorder you can think of: cancer, diabetes, obesity, osteoporosis, heart attack, stroke, depression, cognitive impairment, autoimmune conditions, and more.  The vitamin is required for calcium absorption and is thus essential for bone health, but as evidence mounted that lower levels of vitamin D were associated with so many diseases, health experts began suspecting that it was involved in many other biological processes as well.

Why were so many of us low in vitamin D?  "Vitamin D is a hormone manufactured by the skin with the help of sunlight.  It's difficult to obtain in sufficient quantities through diet."

Enter the settled science that sun exposure is bad.  Excessive sun exposure, particularly sunburn, increases the risk of skin cancer.  Dermatologists recommend absolute protection from the sun, even on cloudy days.  Use sunscreen, the higher the SPF rating the better, and apply it multiple times a day, even if you are just going to work and back.

Easy enough.  Just take a vitamin D supplement every day, stay out of the sun, and all will be well.  Or will it?

"Vitamin D supplementation has failed spectacularly in clinical trials" according to the Outside article.  Five years of high-dose vitamin D had "[n]o impact on cancer, heart disease, or stroke."

Maybe simply taking vitamin D as a pill isn't the same as getting it naturally from sun exposure.  Perhaps the low blood levels of vitamin D in the unhealthy weren't the actual cause of health problems, but instead just a marker.

This is the scientific conundrum of causation versus association.  Does having blue hair cause elderly ladies to play bingo, or is this just an association?

The science of sunlight is a bit more complicated.  The skin uses sunlight to make nitric oxide, a blood vessel-dilator that lowers blood pressure.  This in turn reduces the risk of heart attack and stroke.  Vitamin D is produced along the way but may not be preventing actual disease, instead serving as a marker that an individual is receiving enough sun exposure.

But too much sun, particularly sunburn, does increase the risk of skin cancer.  Some types, like basal cells, are a cosmetic nuisance, whereas melanoma is deadly.

Much as with climate.  One can argue that fossil fuel consumption is a threat to the climate.  Yet the benefits of fossil fuel energy production have lifted millions out of poverty, prolonging life spans and quality of life.

A Swedish study tracked 30,000 women over 20 years and found that "[s]un avoiders were twice as likely to die as sun worshippers."

What unsettled the science of lathering on sunscreen or avoiding the sun altogether was the finding that "[a]voidance of sun exposure is a risk factor of a similar magnitude as smoking, in terms of life expectancy."

How else to explain our prehistoric ancestors, wearing minimal, if any, clothing, spending their days in the sun, without becoming extinct?  Settled science looks simplistic, much in the way Al Gore's insistence the CO2 controls the Earth's thermostat looks simplistic when we consider that the upper Midwest was once covered in a mile-thick sheet of ice when the planet cooled but then melted when the planet warmed.

It seems that sun exposure, in moderation, may not be bad for you.  In fact, it may be healthier than avoiding it.  Does this sound familiar?

In the annals of settled science, we have heard this song before.  Once upon a time, margarine was good and butter was bad.  Margarine is a trans fat and now considered unhealthy compared to butter.  Dietary fats in general were unhealthy, and people were told to eat carbohydrates instead.  This ushered in an epidemic of Type 2 diabetes.

Same with coffee, at one time the cause of all types of nasty diseases, now providing numerous health benefits.

Don't forget carbon dioxide, which, some say, is killing the planet.  Constituting only 0.04% of the atmosphere, does a small increase in CO2 mean the planet is doomed?  Or is it beneficial, since CO2 is plant food, necessary for photosynthesis, responsible for "greening" the planet – which in turn leads to more food production?

There's temperature as well, which fluctuates on the Earth in varying cycles for unclear reasons.  Warmer temperatures might raise the sea level a few inches but may also increase the amount of fertile land and provide a longer growing season.

Although we know much about the world, there is plenty we don't yet understand.  It's the height of hubris to assume we have all the answers and that the science is settled.  The sunscreen about-face is just the latest example.

Brian C Joondeph, M.D., MPS is a Denver-based physician and writer.  Follow him on Facebook, LinkedIn, and Twitter.