The Most Important Study of the Mediterranean Diet Has Been Retracted (qz.com)

Zorro shares a report from Quartz: In 2013, the New England Journal of Medicine published a landmark study that found that people put on a Mediterranean diet had a 30% lower chance of heart attack, stroke, or death from cardiovascular disease than people on a low-fat diet. It received massive media and public attention when released, and since has been cited by 3,268 other scientific papers. The study had tremendous impact on the field of nutrition and health science. Yesterday (June 13), however, the journal retracted the study -- providing a new reason for skepticism about how effective the now-popular Mediterranean diet really is.

The reasons for the withdrawal are complicated, having to do with the methodology of the study. As Alison McCook of the Retraction Watch blog writes for NPR, this retraction is the result of the work of John Carlisle, a British anesthesiologist and self-taught statistician. Carlisle has spent recent years analyzing over 5,000 published randomized controlled trials (the gold standard of medical science research) to see how likely they were to have actually been properly randomized. In 2017, he reported his results: at least 2% of the studies were problematic. One was the 2013 NEJM article on the Mediterranean diet.

Comments

Nothingburger

[Jodka]

The summary is misleading because it omits mention that the randomization errors were inconsequential. The study conclusion remains the same when the improperly randomized subjects are excluded.

from the linked article:

It turns out approximately 14 percent of the more than 7,400 study participants hadn't been assigned randomly to either the Mediterranean diet or a low-fat one. When couples joined the study together, both had been picked to follow the same diet. At one of the 11 participating study sites, the lead investigator had assigned the same diet to an entire village and didn't tell the rest of the investigators.

"This affected only a small part of the trial," says Martínez González. When the researchers reanalyzed the data excluding the nonrandomized people, the results were the same, he adds.

MSM at its finest

[Okian Warrior]

First, some background:

Statistical methods are based on what are known as "stable distributions". A stable distribution is one where a subset of examples, selected randomly, will have the same characteristics as the full set. Normally this refers to a bell curve, so if you have a bell curve population and you select a sample at random, then the sample mean will tend towards the population mean and the sample width will tend towards the population width.

It is this characteristic that lets us extend measurements of characteristics from a subset to the characteristics of the whole population.

(There are a couple of other distributions that are stable, but they are fairly rare in the real world. IIRC, Nile river flooding follows a Levy distribution, and was the first instance of a stable distribution that wasn't a bell curve.)

This only works if the subset selection is random. If the selection isn't random, then the results can be skewed towards randomness (you won't see an effect that's there, the most likely outcome) or phantom effects that aren't really there.

That is the defect in the Mediterranean diet study, that the participants were not placed on one diet (or the other) at random. In particular, husband and wife participants were both placed on the same diet, and in one case an entire town of participants were placed on the same diet.

Of note: When the flawed placements are deleted from the data, the Mediterranean diet still stands and there is still a clear effect indicated by the data.

"This affected only a small part of the trial," says Martínez González. When the researchers reanalyzed the data excluding the nonrandomized people, the results were the same, he adds.

So the conclusions of the study are still strong: the diet correlates well and strongly with reduced heart attacks.

Out of an abundance of caution and professional ethics, the study was adjusted with softer language in the conclusions.

And yet, our noble MSM is reporting only that the study was retracted, comparing it to 50-ish other studies that were similarly flawed.

With predictable results, such as the post this is in reply to.

(Exercise for the reader: Is the MSM doing more harm than good here, or is it the other way around? Many, many other articles report the news with an opinion, such as "Trump meets with Kim, but it won't result in anything useful". Why couldn't NPR have a similar headline for *this* article, such as "Diet study retracted, despite being accurate"?)

Re:MSM at its finest

[pots]

And yet, our noble MSM is reporting only that the study was retracted, comparing it to 50-ish other studies that were similarly flawed.

Did you read the links? The NPR link says basically what you're saying here: the diet still has good evidence behind it, but they softened the language in the conclusion as a result of this. The Quartz article is more one-sided, but... are you really calling Quartz "MSM"?

Let's see... Here's the New York Times coverage. I'll quote:

That Huge Mediterranean Diet Study Was Flawed. But Was It Wrong?
A highly publicized trial in Spain found that the Mediterranean diet protects against heart disease. Now the original work has been retracted and re-analyzed, with the same result.

The next link from my search is USA Today, I'll quote:

He stressed this flaw only affected a small part of the trial (about 10 percent of participants) and that the conclusions remain the same: A Mediterranean diet can decrease risk of heart attacks and strokes by about 30 percent among those who are at high risk of developing cardiovascular disease.

So the answer to your exercise appears to be: Yes, the MSM are responsible journalists and the random news blog is not.

Re:Anything you eat will kill you

[blindseer]

There are many animals in this world in that if you give them an unlimited supply of food, they will keep on eating until they die; often in very short order.

I grew up on a dairy farm and I'd see this happen. I personally didn't see a cow eat itself to death but I have seen cows eat until they got sick and had heard stories of people having to dispose of cows that had eaten until they died. This seems to only be true of corn feed though, a cow will know enough to stop eating grass/alfalfa/haylage eventually. I do remember a calf that didn't know enough to not eat the straw. That calf got bloated and sick constantly until it learned that straw is not good food.