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Comment & Response
December 24/31, 2019

Healthy Diet and Risk of Dementia in Older Adults

Author Affiliations
  • 1School of Food Science and Engineering, South China University of Technology, Guangzhou, China
  • 2Department of Microbiology, Immunology, and Cancer Biology, University of Virginia, Charlottesville
JAMA. 2019;322(24):2444-2445. doi:10.1001/jama.2019.17942

To the Editor Dr Lourida and colleagues found an association between unfavorable lifestyle and genetic risk with a higher incidence of dementia.1 We wish to draw attention to several issues that we believe could have affected the results.

In assessing the dietary component of the healthy lifestyle index (smoking status, physical activity, diet, and alcohol consumption), the authors defined a healthy diet as the consumption of at least 4 of 7 common food groups (fruits, vegetables, fish, processed meats, unprocessed red meats, whole grains, and refined grains). We believe this model is too general and does not adequately account for important dietary essentials. Per the model, a person could be consuming fish (≥2 servings/wk), processed meats (≤1 serving/wk), unprocessed red meats (≤1.5 servings/wk), whole grains (≥3 servings/d), and refined grains (≤1.5 servings/d) and still be considered as having a healthy diet, even without adequate fruit and vegetable intake. In addition, individual foods differ in nutrients and nutritive values. For example, different varieties of fruits (banana, apple, and watermelon) and meat (pork, beef, and mutton) have different energy, fat, and nutrient values, which were not accounted for. Consuming a variety of fruits may be better than meeting the recommended fruit intake with just a single type. The association between fruit and vegetable consumption and dementia risk is reported to be greatest for green leafy vegetables and berries.2 Total energy and nutrients consumed were not adjusted for in the analysis.