As a cardiologist, I recommend that many of my patients follow a Mediterranean diet. This diet, rich in the more healthy fats such as olive oil and nuts, is easy to follow. It is nutritious, and avoids processed food and the kinds of processed carbs that make you gain weight. Perhaps most important, there was a tremendous amount of research to suggest that the diet decreased your risk of having a heart attack or stroke.
So imagine my dismay when a groundbreaking trial evaluating the Mediterranean Diet, published in the New England Journal of Medicine in 2013, was recently retracted. Retracted is a kind way of saying, “We made a mistake.” In the same journal, five years later, the authors were allowed to publish a new, revised article accounting for their mistakes. This rarely happens. In the sports world, this is called a do-over. Imagine if New England Patriots quarterback Tom Brady, of Deflate-gate fame, was allowed to have a do-over in the last Super Bowl, against the Eagles, after he fumbled in the final minutes. It would have challenged the integrity of the game.
Here is what happened in this more recent New England scandal, which could be referred to as “Diet-gate.”
One of the hallmarks of a good study is that participants are randomized to different groups, and this must be done without input from the researchers. If the 2013 study had been conducted correctly, each participant, by virtue of a computer-generated coin flip, would go to one of three groups in the trial. Each person would either supplement a diet with olive oil or nuts, or follow a low-fat diet. That is how the study was originally reported. The original results: The two groups that supplemented reduced the relative risk of cardiovascular disease (heart attack or stroke) by 30 percent.
But just last week, it was found that the researchers cheated a bit when they randomized some of the participants. In one case, an entire village was placed into the same dietary cohort. Apparently, some people were getting free olive oil, and their neighbors became jealous. So, the researchers gave everyone in the village free olive oil, then moved them all into the same group of the trial. The amount of free extra-virgin olive oil was one liter a week (versus getting a measly 30 grams of mixed nuts a day or nothing at all in the control group) so it is easy to see why some folks became jealous. But this change led to more than 1,500 of the 7,447 participants not being treated correctly. And the researchers did not report what they had done.
When the editors of the NEJM realized what happened, they asked the original researchers to reanalyze their data. This took a whole year, and involved statistical adjustments to account for the mistake. The new paper is not much different, as their initial conclusions were accurate and diets supplemented with olive oil or nuts seemed to be associated with a lower risk of heart problems. But the results from this study become less valid because of sloppiness by the researchers.
What conclusions can be drawn from this mistake? We are all bombarded with medical news all the time, and it is hard to know what to trust. Usually, studies that pass the scrutiny required of articles published in top medical journals can be counted on to be accurate, and medical professionals need this to help advise their patients. Even though the Mediterranean diet is still a good diet for most of us, this story makes it even harder to filter out valid medical news.
What is most interesting to me is that a major flaw of the study was never addressed. Participants in this 2013 trial followed a low-fat diet (which does not really work for many people) compared with a Mediterranean diet supplemented with either a liter of olive oil a week or daily nut supplementation. To me, this concept seems flawed as we should not need to pour olive oil on our food in large amounts, nor should we be forcing ourselves to eat nuts every day to be healthy. Instead, we should be working toward following a diet rich in fruits and vegetables, as well as exercising regularly.
David Becker, M.D., is a frequent Inquirer contributor and a board-certified cardiologist with Chestnut Hill Temple Cardiology in Flourtown, Pa. He has been in practice for 25 years.