This release describes a study by Cleveland Clinic researchers who assigned a group of volunteers with overweight and obesity to a diet either rich in whole grains or one with refined grains. Each diet contained the same nutritional values but the whole grain diet consumers experienced a lowering of their diastolic blood pressure, which the researchers say lowers their risk of developing cardiovascular disease. But lowered blood pressure was a surrogate outcome, not a reduction in risk as the release claimed. It would take a larger outcomes study to determine if the diet reduced cardiovascular risk.
The release also points to reductions in relative risks rather than absolute risks, fails to mention costs or any potential harms from such diets, and neglects to state that three of the 11 authors work for the funding company, which also makes whole-grain foods.
As the release explains, high blood pressure affects 30 percent of adults in the United States and is a major risk factor for cardiovascular disease. If changing one’s diet to incorporate more whole-grain foods can substantially lower blood pressure, and perhaps reduce disease risk, then this would represent a public health gain.
The release may too strongly link obesity and hypertension. While no doubt obesity increases risk, plenty of people without obesity also have hypertension.
There were no mentions of costs in this release, which is unfortunate since a simple statement could have informed readers that both whole grain foods and refined grain foods are readily available and are usually similar in cost.
The release states that, “While on the whole grain diet, participants saw a three-fold improvement in diastolic blood pressure (the lowest pressure when your heart relaxes between beats) compared to the refined grain diet. This improvement equates to reducing the risk of death from heart disease by almost one-third, and the risk of death from a stroke by two-fifths.” However that is a relative risk reduction, not an absolute risk reduction which would have provided readers with a better understanding of the observed change.
The release also said, “Overall, there were substantial reductions in body weight, fat loss, systolic blood pressure, total cholesterol, and LDL cholesterol during both diet periods,” but provided no numerical data explaining those reductions.
There is no mention in the release of any harms arising from a diet rich in whole grains but we won’t fault them from that. The benefits of whole grain foods have been well documented.
Providing more detail on what the diets contained would have been helpful to readers.
This release explains that the research involved a “double-blind, randomized, controlled crossover trial” that provided data that “cannot be obtained from large observational studies.”
However, the lowered blood pressure was a surrogate outcome and not a primary endpoint, i.e. reduced risk of cardiovascular disease. It would take a much larger outcomes study to demonstrate that.
The release also described the research as “one of the largest controlled studies of its kind,” although it still only involved 33 participants and ran for two eight-week periods.
The release identifies the funders of this research as both the National Institutes of Health and the Nestlé Corporation and points out that Solon and Cereal Partners Worldwide provided “the study meals and foods.” However, it does not mention, as the published study does, that three of the authors work for Nestlé.
Since the study itself is a comparison between diets rich either in whole grains or refined grains, it’s obvious that there are a multitude of diet alternatives.
As mentioned above, more details on the contents of the diet would have been beneficial.
Whole grain foods are readily available at grocery stores and markets, so availability is not an issue here.
The release establishes novelty with its claim that the Cleveland Clinic and Nestlé researchers “conducted one of the largest controlled studies of its kind.” A study group of 33 seems small to be called “one of the largest” but the release doubles down on novelty as it further explains:
“The uniqueness of this study is that each of the 33 participants consumed both diets,” said Kirwan (the lead researcher). “This level of control can only be performed for small numbers and provides the essential empirical data that cannot be obtained from large observational studies.”
While the release should have done more to clarify that “one of the largest” studies is still quite “small,” we’ll give the benefit of the doubt.
No unjustifiable language here.
Systematic, Criteria-Driven
Monday at #ADA2021, an infectious disease epidemiologist, a journalist, and a researcher shared perspectives on communication of risk in the era of COVID-19: http://ow.ly/ROfR30rMeE7 @AstleyCM @garyschwitzer @berthahidalgo @ADA_DiabetesPro
Shoutouts to @susan_bewley @drkevinknopf @MichaelBaum11 in this call for more than fawning coverage from press releases for these kinds of stories.
Also, linked history inside goes back 5 years just on Grail apparently trying to become Holy Grail. https://twitter.com/garyschwitzer/status/1408849696416841731
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