September 12, 2018
Maintaining a healthy diet in midlife is independently associated with a larger hippocampus years later and may protect against mental illness and cognitive decline, researchers say.
"This is the first major study to investigate long-term diet impact at midlife on hippocampus structures. Our study contributes to the growing body of evidence that shows overall diet impact on mental health," lead investigator Tasnime Akbaraly, PhD, from the French Institute of Health and Medical Research (INSERM) and the University of Montpellier, told Medscape Medical News.
"Thus, routine dietary counseling as part of a doctor's office visit, especially with mental health practitioners, is of importance at a patient's level, but sound dietary counseling should also be a high-priority public health goal," said Akbaraly.
The study was published online July 26 in the American Journal of Medicine.
Better Diet, Bigger Hippocampus
The findings are from the Whitehall II brain imaging substudy and involved data from 459 participants (average age at baseline, 49 years). Diet was assessed with a food-frequency questionnaire, which was administered in 1991-1993 and 11 years later, in 2002-2004. At the end of follow-up in 2015-2016, participants underwent multimodal MRI of the brain.
Higher cumulative average score on the Alternative Healthy Eating Index 2010 (AHEI-2010), which reflected long-term healthy diet, was associated with a larger total hippocampus volume. Each 1 standard deviation (SD, 8.7 points) increment in AHEI-2010 score was associated with an increase of 92.5 mm3 in total hippocampal volume, the investigators report
This association was independent of sociodemographic factors, smoking habits, physical activity, cardiometabolic factors, cognitive impairment, and depressive symptoms and was more pronounced in the left hippocampus than in the right hippocampus.
A healthy diet, as reflected by AHEI-2010 score, is rich in vegetables, fruits, whole grains, nuts, legumes, omega-3 fats, and polyunsaturated fatty acids, and is light on sugar-sweetened drinks, red and processed meat, trans fat, and sodium-rich products. It is also characterized by low alcohol intake. In the current study, low alcohol intake was a "key component" associated with larger hippocampus volume, the researchers say.
"Our findings lend support for the hypothesis that overall diet may affect brain structures with a specific impact on hippocampus volume," the researchers conclude. "Accounting for the importance of hippocampus with long-term, declarative, episodic memory, as well as for flexible cognition network, our findings reaffirm the need to recognize diet and nutrition as potential determinants of cognition, mental health and social behavior."
Commenting on the findings for Medscape Medical News, Felice Jacka, PhD, director of the Food and Mood Center at Deakin University, Geelong, Australia, said this study "highlights again the importance of good nutrition to the brain across the life course.
"We are currently in a situation where poor diet is now the leading cause of early death across middle and high-income countries and the number two cause globally. At the same time, mental disorders impose the highest burden of disability. The fact that these two leading health challenges are linked has important implications," said Jacka, who is president of the International Society for Nutritional Psychiatry Research.
In 2015, as reported by Medscape Medical News, Jacka and colleagues showed that diet quality was linked to the size of the hippocampus in older adults. That study showed that the hippocampus was smaller in people who consumed an unhealthy Western diet and was larger in people who consumed healthier diets.
"Dr Akbaraly's study extends this by showing the association between diet and hippocampal size in midlife and over time and by drilling down into the particular aspects of diet that may be important," said Jacka.
"As we age, our hippocampus shrinks, and this is associated with cognitive decline. Thus, these studies point to the importance of diet for preserving our brain power as we age, but they also suggest that diet is of relevance to our brain health and cognitive abilities across the lifespan," she added.
The study had no commercial funding. Dr Akbaraly and Dr Jacka have disclosed on relevant financial relationships.
Am J Med. Published online July 26, 2018.