The HealthDay story failed on many fronts – no mention of the study’s limitations, no mention of harms, and a touting of the benefits of berries without further discussion of the evidence. 2 stars here, 3 for TIME, 4 for NPR.
The main failures of the story are caution in interpreting observational studies and failure to consider alternative hypotheses, such as that potassium from the berries may have accounted for this finding.
The story never mentioned that such observational studies – based on people keeping a diary of habits and self-reporting – has innate limitations. And they cannot prove cause and effect – only a statistical association. These are significant omissions. We offer a primer on this topic that would help journalists and the public.
Another limitation that was not discussed in the article was that researchers think that a specific compound called anthocyanin may be responsible for any reduced risk for heart attack that might be at play. But the problem is that they’re not completely sure, since the amount of anthocyanin in the body cannot be measured. They acknowledge that another compound may be responsible.
Then, there were the things that were not mentioned in the story – no discussion of prior research, harms, study limitations and alternatives.
The story touts berry consumption, when the true benefits of anthocyanins are questionable, as reported by the study. More supporting evidence is needed, before the article can make such dietary recommendations. Younger women need to focus on avoiding overweight/ obesity, and behaviors such as exercise and not smoking as the best way to avoid premature heart disease. These are much stronger risk factors than anthocyanin consumption.
Not applicable. Costs not mentioned but we think most readers know the ballpark costs of berries.
The study focused on the different subsets of flavonoids and looked to see whether there were any health benefits associated with five specific ones (flavonols, flavones, flavanones, flavan-3-ols and anthocyanins). The study also looked at flavonoid polymer and noted that it remains poorly defined, which is probably why the results for this subclass was not emphasized, despite being statistically significant.
The article mentions that there is a 32 percent reduction in risk for heart attack, but this is the figure associated with only anthocyanin, after adjustment of multiple variables. The story fails to mention that increased consumption of all other flavonoid subclasses did not show a significant statistical association.
The true impact of increased anthocyanin intake is also questionable. The original journal article states: “There are currently no specific biomarkers for anthocyanins because there is currently a limited understanding of their degradation and metabolism after ingestion. It is possible that our findings for anthocyanins might be due to other constituents found in the foods that contribute most to this subclass.”
The story did not discuss potential harms, but all health interventions have harms, as well as benefits.
The story failed to identify any of the study’s limitations.
At a minimum, the writer should have identified that this is an observational study and that there are always additional (uncontrolled) factors that can result in incorrect findings, particularly in secondary analyses of diet and disease outcomes over time. Observational studies cannot prove cause-and-effect, yet this story was filled with discussion of “benefits” that cannot, indeed, be established in such a study. Strong statistical association in a large sample – YES. Cause-and-effect showing benefit – NO. Read our primer.
There is no disease mongering.
The story quotes two independent experts, preventive cardiologist Dr. Suzanne Steinbaum and nutritionist Dana Greene. We wish that the experts were quoted on a more analytical view of the study, instead of talking so much about berry diets. Greene is even quoted as saying, “[Berries] are so good for you,” and “There is no downside” to eating berries. Again, too much of anything could become more of a harm than a benefit, as mentioned above. It’s interesting that Steinbaum was also interviewed in the competing TIME story. Why?
No alternatives are mentioned. To prevent heart attacks, patients can either take medications, such as blood-thinning and cholesterol-lowering drugs, or make lifestyle changes, like maintaining a healthy weight, exercising and not smoking.
The availability of strawberries and blueberries is not in question.
The story does not mention that previous studies have addressed the beneficial effects of flavonoid consumption on heart risk. The researchers studied which specific classes of flavonoids might reduce the risk for heart attacks.
The lede of the HealthDay story is almost identical to the press release, and the story uses similar language as the release. However, there is evidence of original reporting with the two independent sources. Barely satisfactory.