The Best Foods for Thought, Literally

Does the story adequately quantify the benefits of the treatment/test/product/procedure?

Not Satisfactory

When you find this story online on WSJ.com, it carries the banner:  “The Diet That Saves The Brain.”

The Diet That Saves the Brain – WSJ.com

There isn’t any discussion in the body of the story to back up that bold claim.

We don’t blame the reporter for this but someone at WSJ has to take responsibility for this hype.

We’ll also add this to our wish list: an explanation that higher “white-matter volume burden” is a surrogate measure of health — i.e. it does not necessarily translate to more brain damage. These white spots are often found in normal people and might not mean anything. The differences the researchers found were statistically significant, but there’s no attempt to sort out whether the changes observed are clinically meaningful.

Does the story seem to grasp the quality of the evidence?

Not Satisfactory

The researchers actually published a long paragraph of potential limitations, which we include here to show that a simple line at the end of the story – cautioning “that the study doesn’t prove that a Mediterranean-style diet causes less brain damage and said more study is needed” – doesn’t really get at an independent evaluation of the evidence – something an independent expert could have provided as well.

The researchers wrote:

A MeDi (Mediterranean Diet) was associated with a lower WMHV (brain magnetic resonance imaging white matter hyperintensity volume) burden, a marker of small vessel damage in the brain. However, white matter hyperintensities are etiologically heterogenous and can include neurodegeneration.

…

However, our study has several limitations. We only measured food frequency at baseline, which was on average 7 years before the time of MRI WMH assessment (range, 2-14 years), and thus participants could have changed their diet before the MRI was performed. However, dietary patterns appear to be stable in other population-based studies. In addition, despite the use of a valid and reliable food frequency questionnaire to calculate MeDi scores, a potential for both random and systematic misclassification of dietary habits persists, although any misclassification is most likely to be random and thus tending to minimize an association between a MeDi and WMHV. Most studies depend on similar methods, and they are a practical approach, albeit subjective in nature. In addition, we used the traditional MeDi score method to quantify adherence, but this too has limitations because the score is based on the cohort- and sex-specific median values across 9 food categories, which does not readily allow for an examination of dose-dependent associations. However, most population-based studies have used this approach. Although the potential for confounding always exists, the persistence of associations after adjustment for many potential confounders suggests that this form of bias does not account for the associations observed. The MRI study population represents a subcohort of the overall NOMAS cohort and was younger and generally healthier than the full cohort. However, as mentioned previously, we did not observe diet differences between those who were included and excluded, again suggesting that selection into the study cohort did not bias our results. Last, MRIs to measure WMHV were only conducted once, so we are unable to infer the temporal association between the MeDi and development of WMHs.

Does the story use independent sources and identify conflicts of interest?

Not Satisfactory

No independent perspective provided and – if the journalist isn’t going to do a critical analysis of the evidence – then an independent perspective is sorely needed in such stories.

Does the story compare the new approach with existing alternatives?

Not Satisfactory

The story didn’t even include a line about other stroke prevention research – dietary or otherwise.