The MIND Diet Comes Up Short in Dementia
New research today in the New England Journal of Medicine offers an important lesson – for anyone with an open mind. Finding an association of a dietary pattern with a better health outcome is not the same as showing that a dietary pattern has that effect. Eight years ago, Martha Clare Morris and colleagues told us the “MIND diet slows cognitive decline with aging.” But in fact, all they had found was an association. The new study in NEJM, a randomized controlled trial of the MIND diet for preventing dementia, finds no effect.
Some people are ready to hear this. Others are not.
Not Ready for a Null Result
For a insight into the people who are not ready to accept these results, a quick read of CNN reporting on this study will suffice. The lead investigator, Lisa Barnes, told reporters:
“We really expected that the MIND diet would show an effect above the control group, so we were quite surprised by the outcome.”
So she was quick to point to earlier studies that were more positive. She explained that the difference was a longer duration in those earlier studies. No mention pops up in this reporting of a most important difference – the earlier studies were observational. They merely document an association with a benefit. Not a cause and effect relationship.
Other experts were eager to step up and defend the presumption of a benefit. Walter Willett told CNN:
“My main concern with this trial from the beginning has been that three years may be too short a time to have an impact on a disease process that develops over many decades.”
Food Is Not Medicine
Perhaps the problem is one of unrealistic expectations. So much hype about the MIND diet may have set up expectations that a dietary intervention can seldom meet. Otherwise credible experts in nutrition keep bombarding us with their belief that “food is medicine.” But it is not. It is nourishment and it’s necessary for good health. But it is not a substitute for effective medicines when these are needed.
For a stark contrast, consider the effect of donanemab – a monoclonal antibody for clearing amyloid plaque in patients with early Alzheimer’s disease. A study published this week in JAMA showed donanemab slowed the decline in cognitive function over just 72 weeks of therapy. This trial was less than half the duration of the MIND diet study.
This evokes no rationalization about needing to wait longer to see an effect.
Waiting for Prevention to Kick In
Repeatedly, we encounter people rationalizing the lack of an observable prevention effect for their favorite dietary intervention. “We must be patient and wait for the effectiveness to become apparent. These things take time.” They tell us this with great conviction.
When a prevention strategy is not working and advocates insist we must wait for an effect to appear, more often than not, the problem progresses. Then we find that we have been waiting for Godot and he never comes.
Click here for the study of the MIND diet, here, here, and here for other reporting on it.
Old Winegrower in Moret, painting by Camille Pissarro / WikiArt
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July 19, 2023
