Kevin Lomangino is the managing editor of HealthNewsReview.org. He tweets as @KLomangino.
[Editor’s note: This post has been updated with a response from BMJ. Scroll to the bottom for details.]
BMJ’s public relations team is at it again: putting overstated headlines on news releases about observational nutrition research that can’t support the claims.
This time it was on a Chinese study, published in the journal BMJ Heart, purporting to show that “Daily egg consumption may reduce cardiovascular disease.” They even quantified the exact percentage that eggs may reduce your risk in the release’s subheadline: “Having an egg a day could reduce risk of stroke by 26%.”
We’ve repeatedly criticized BMJ news releases that made similar claims in the past.
Whether or not you agree with oncologist and nutritional epidemiology critic Vinay Prasad, MD, who says these types of studies amount to little more than “garbage” (more on his thinking in this “tweetorial”), one thing is for certain: the BMJ characterization of this study stinks.
The news release leads with a headline that clearly makes a cause-and-effect claim about eggs reducing risk, and waits until the 16th paragraph to provide the all-important qualifier: “This was an observational study, so no firm conclusions can be drawn about cause and effect.”
If no such conclusions can be drawn, why frame the study with a statement that clearly invites such a conclusion? The release could just as easily have been headlined, “Daily egg consumption may not reduce cardiovascular disease.”
Of note, the title of the study itself was much less definitive and more accurate than the news release headline: “Associations of egg consumption with cardiovascular disease in a cohort study of 0.5 million Chinese adults
Predictably, some news outlets ran with the scrambled BMJ news release framing, taking readers for another spin on the “good for you one week, bad for you the next” nutrition research merry go round. Some early headlines:
Medical News Today: One egg per day may keep stroke at bay
Some stories, like this Agence France Presse piece headlined (unsurprisingly) “An egg a day may keep the doctor away, study claims” did mention some limitations. It cautioned that the daily egg consumers were more affluent than those who didn’t consume eggs and that this difference might have biased the results.
Similarly, this Gannett piece headlined “Eggs, once thought to be bad for heart health, now considered OK” noted that the biggest egg eaters in the study consumed less than one egg a day on average — far less than many Americans.
Newsweek did even better to suggest caveats right in its headline: “SCIENTISTS LINK EGGS TO LOWER HEART DISEASE RISK—BUT ARE THEY ALL THEY’RE CRACKED UP TO BE?”
But other coverage, including the superficial pieces from TIME, CNN, and the BBC, featured little if any discussion of the study’s significant limitations – shortcomings so grave that they could represent fatal flaws in the design, experts said.
That’s little surprise since the BMJ news release also omitted any mention of those limitations other than the fact that it was an observational study.
“It’s ironic that we’ve flipped from eggs are bad to you to eggs are good to you again,” said Christopher Labos, MD, a cardiologist and HealthNewsReview.org contributor.
He noted that the study relied on food frequency questionnaires, which are known to be unreliable because people simply can’t accurately remember what they eat over a long period of time. “In this study, people were asked to remember how often they ate eggs over the past year, which is almost impossible for someone to remember accurately,” Labos said. “How often did you eat eggs over the past year? I for sure don’t know how often I did.”
“Second this is an observational study, and the people who ate eggs more often could very easily have been different in a fundamental way from the people who did not. In this study the people who didn’t eat eggs smoked more, had lower income, and had higher blood pressure so were probably more at risk for cardiovascular disease. You can attempt to adjust for these differences statistically but you can never do it completely.”
Kathleen Fairfield, MD, DrPH, a clinician-scientist based at Maine Medical Center, also flagged confounding as a major concern with the study. And she said the language and framing used in the release was likely to mislead the public. “Only randomized trials should be interpreted with causative language,” she said. “The title should have at least used the words ‘eggs may be associated with…’ In general, we know that certain dietary patterns are associated with lower CVD risk (ie. fewer processed and prepared foods, more vegetables and lean protein), and the story should have emphasized healthy eating patterns rather than a specific food, which adds to public confusion.”
This is not an argument against the daily consumption of eggs; it’s a plea not to delude ourselves into thinking eggs are some kind of magic medicine for preventing heart attacks and strokes.
The emphasis placed on specific foods in these types of studies facilitates the spread of misinformation, said Yoni Freedhoff, MD, a nutrition and weight management expert at the University of Ottawa and a HealthNewsReview.org contributor.
“The day that medical journals stop publishing studies suggesting specific benefits or risks to single foods cannot come soon enough,” Freedhoff said. “Not only are these types of studies fatally confounded and built off of known-to-be-hugely-problematic dietary recall, but their publication fuels actual quacks by lending credence to their regularly flogged notions that there are dietary demons and deities where if you eat this one thing you’ll either help or hinder health.”
[Correction: A quotation in an earlier version of this post stated that people who ate eggs in this study smoked, had lower incomes, and higher blood pressure than people who didn’t eat eggs. In fact, it was people who didn’t eat eggs who had these characteristics. The quotation has been revised.]
BMJ media relations manager Emma Dickinson emailed the following response to the concerns raised in this post:
“Thank you for picking this up and we take your comments on board. We do put a great deal of effort into getting our press releases right. But occasionally, one slips through the net, as seems to have happened here, for which we take full responsibility. Our media and editorial teams have reflected on the issues raised here and, as a result, we are now undertaking a formal review of our checking and signing off processes for journal press releases.”