Everything bad is good again. Until we are told by the experts that it has been changed back.

In our era, we’ve grown accustomed to having one study supersede another; to seeing one recipe for health turned completely on its head when another body of experts takes a second look at something that had seemed settled. But it used to be that changes were years, or decades, in the making.

Not these days. Last week’s big news on cholesterol didn’t even make it through the weekend.

The headlines last week: Millions more may need statins to lower cholesterol.

The headlines on Monday: Never mind.

One problem with these kinds of changes, of course, is that the people will soon enough simply tune out.

It’s unfortunate because there are, in fact, a few verities, though it’s not a little difficult to get a handle on them when recommendations seem to come and go like the tides.

The butter vs. margarine battle is a prime example.

Those who are old enough to remember when butter was deemed suddenly unhealthful — doubtless just shook their heads when, decades later, margarine came to be seen as a tub full of trouble.

What was wrong with the latest cholesterol study? An online calculator at the heart of the new world order was found to be badly flawed. It flagged millions and millions of people who were likely quite healthy as needing treatment for high cholesterol.

And it didn’t have to happen, as a review of the findings, before the study was released, had caught the error. But nothing was done.

Do you need to take medication to lower your cholesterol? Maybe, or maybe not. You could talk to your doctor, but just make sure he isn’t relying on that new online calculator.

— The Republican of Springfield (Mass.)