The story compares the effects on Alzheimer’s disease of a Mediterranean diet, the DASH (Dietary Approach to Stop Hypertension) diet, and a hybrid of the two, the MIND (Mediterranean-DASH Intervention for Neurodegenerative Delay) diet. The story focuses on the specific elements of the diet without critically appraising the research itself, and helping readers understand the limits of observational studies. Additionally, the story does not raise the issue that only relative risks were reported in the study, not absolute risk of Alzheimer’s, making the impact of the diet appear greater than it is.
As the population ages, Alzheimer’s disease becomes more prevalent. Dietary approaches to other diseases, such as hypertension and diabetes, are common and well researched in the scientific literature. A diet that includes components of the anti-hypertension DASH diet and the heart-healthy Mediterranean diet that is protective against the cognitive degradation of Alzheimer’s disease could help reduce the burden of the disease.
There is no discussion of the costs of the diets in this story. Some parts of the diets, including berries out of season and greens year round, can become expensive. The types of foods included in this diet are not necessarily readily available in economically depressed areas of the US. A quick nod to either of those facts would have earned the story a satisfactory rating.
The evidence for the efficacy of the MIND diet over the DASH diet and Mediterranean diet exists in the paper, but is not fully conveyed in the story. It was challenging for the story to quantify benefits from the study because the paper itself did not publish any absolute numbers or percentages in the key tables or in the text of the article, making it impossible to calculate absolute risk reductions without pressing the study authors for more information. We are holding the bar high here, but unapologetically so, because we believe that provision of only relative risks gives a misleading and inflated estimate of benefit. The story says that the MIND diet can provide a 53 percent reduction in the risk of Alzheimer’s Disease. While this may be technically accurate, the true size of the benefit is impossible to gauge without knowing the overall rate at which participants developed Alzheimer’s disease in the study. In addition, the story could have noted that the Mediterranean diet was reported at 54 percent reduction when closely followed, too. One of the most important findings was for those who don’t follow diets perfectly, but perhaps moderately. The story makes a reference to this, but it does not include how well the other diets performed when only moderately followed.
Following any of these three diets is better than the normal, high fat, salt and red meat standard American diet and even moderate adherence to these diets is thought to be heart healthy and perhaps brain healthy, too.
This is a very well conducted and carefully analyzed nutritional epidemiology study, funded by NIH funds and carried out by leaders in the field. At the same time, the authors of the study recognize the limitations of their scientific approach and do not attempt to overstate the findings. The story missed the opportunity to talk about the main limitation to observational studies of diet and disease, namely that we can only discuss association, not causation (which would require a randomized trial). The authors clearly state this limitation in the discussion of the article:
“The primary limitation of the study is that the observational study design precludes the interpretation of the findings as cause and effect. Randomized dietary intervention trials would be required to attribute causal effects of the diet patterns to the development of the disease.”
There is no disease mongering in this story. The prevalence of Alzheimer’s Disease is increasing and if dietary changes can prevent or delay the disease, they should be considered.
There appear to be no independent sources used in this story. The paper indicates that there is no conflict of interest for the authors, so no mention of conflict is acceptable. A comment by an expert not affiliated with the study would have provided context.
This story compares two of the alternatives to the MIND diet, the DASH diet and the Mediterranean diet, so we’ll give it a pass here. However, it is unclear from the story what these diets are being compared to and one might assume it is a standard American diet, but it is really a low-fat control diet. The story does not make this clear. The story could have discussed the scoring system used in the study, which was clearly described in the scientific article. In addition, the story goes into quite a bit of detail about what might be okay for people to do with their diet, beyond what the scientific study actually stated.
Certainly all of the components of the MIND diet are available in most supermarkets. While there might be a problem in areas where supermarkets are scarce, overall the diet’s foods are available. This would have been easy to mention in the story. Since the story did not touch on availability, however, we’ll rate this Not Applicable.
While diets for cardiac health and to control diabetes and hypertension are common, evaluation of diets to prevent cognitive degradation are unusual. But the story missed the point that this study is the first published article finding that Alzheimer’s (not just cognitive decline) is less common in the people who adhered to the MIND diet.
A news release by Rush University is available online. The story includes enough information beyond the press release that we are satisfied that it did not rely too heavily on it.