Another one bites the dust - Mediterranean Diet study retracted

[TomBAvoider]

By now it's something of a cliche to observe that a ton of studies, including perhaps especially diet related studies, are shoddy and unreliable. Here's another one, plus more evidence that studies in medicine are again questionable:

 

https://www.npr.org/sections/health-shots/2018/06/13/619619302/errors-trigger-retraction-of-study-on-mediterranean-diets-heart-benefits

 

What prompted the Mediterranean diet researchers to soften their language?

A persistent British anesthesiologist named John Carlisle.

He knew very little about analyzing the details behind clinical trials until a few years ago, when he wrote a letter to an anesthesiology journal bemoaning the fact that his field was polluted by one researcher's data that many suspected were problematic. The journal editor told Carlisle, a practicing anesthesiologist at Torbay Hospital in Torquay, England, to prove it.

So Carlisle did. He read up on statistical methods and looked over more than 160 trials by the researcher, Dr. Yoshitaka Fujii, and analyzed how likely it was that the people had been randomized to different treatments. Randomization is part of the gold standard for clinical studies because it reduces the risk of bias and allows researchers to determine cause-effect relationships.

Carlisle found the odds were infinitesimally small that Fujii had randomized people properly. Since Carlisle's findings were published in 2012, medical journals have retracted more than 160 papers by Fujii — the most retractions for any one researcher, by a large margin, according to Retraction Watch.

[Sibiriak]

TomBAvoider: a ton of studies, including perhaps especially diet related studies, are shoddy and unreliable.

 

That's certainly reason to avoid drawing any broad conclusions from any single trial.   On top of that, as Valter Longo  often stresses,  one needs to take into consideration the totality of evidentiary sources (his "five pillars").

 

Regarding this particular Mediterranean Diet study:

 

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.

 

Still, because everybody wasn't randomly assigned to different groups, the study can no longer claim the diet directly caused those health benefits. "We need to tone down the results, but it is just a little bit," he says.