A study published in The American Journal of Medicine 2018, has demonstrated that maintaining a healthy diet in midlife is independently associated with a larger hippocampus years later and may protect against cognitive decline. The hippocampus is a structure located in the temporal lobe of each brain hemisphere and is directly involved in the process of memory. The volume of the hippocampus can be determined by brain magnetic resonance imaging (MRI). Decreasing of its volume is related to cognitive impairment and is used in clinical practice for the diagnosis of Alzheimer’s disease (hippocampus atrophy).
In this study, the quality of the diet of 459 participants (average age at baseline = 49 years) was assessed with a food-frequency questionnaire, which was administered in 1991-1993 and 11 years later, in 2002-2004. At the end of the follow up, around 13 years after the first questionnaire, participants underwent brain MRI with study of the hippocampus. Long-term healthy diet (showed by higher cumulative score on the Alternative Healthy Eating Index), was associated with a larger total hippocampus volume. 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, based on recommendations in the Alternative Healthy Eating Index 2010 (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.
The findings of this study support the hypothesis that overall diet may affect brain structures with a specific impact on hippocampus volume.
Some other studies have demonstrated the influence of diet in brain structures. In most of these studies, diet quality was assessed by Mediterranean diet score, and higher scores (healthier diet) were found to be associated with larger cortical thickness, lower white matter hyperintensity burden, and preserved white matter microstructure. All these findings indicate better preservation of normal brain structure.
Another previous study, published in 2015 in the BMC Medicine, had already shown that higher intakes of unhealthy foods, normally present in the Western diet, were independently associated with smaller hippocampal volume. This finding was originally observed on experimental animal models and suggested that a high-energy diet rich in saturated fats and refined sugars adversely affect neuronal plasticity and function. Animals maintained on a high-energy diet rich in fat and sugar showed lower performances in hippocampus-dependent spatial learning, object recognition, reduced hippocampus levels of brain-derived neurotrophic factor (BDNF) and impaired in blood-brain barrier integrity.
Accounting for the importance of hippocampus with long-term, declarative, episodic memory, as well as for flexible cognition network, this study reaffirms the need to recognize diet and nutrition as potential determinants of cognition, mental health and social behavior.
A Long-term healthy diet (and not various episodic restrictive diets) is the key to promote brain health and prevent dementia.
Thus, routine dietary counseling as part of a doctor’s office visit is very important at a patient’s level, but it should also be a high-priority public health goal.
- Akbaraly, T et al. Association of Long-Term Diet Quality with Hippocampal Volume: Longitudinal Cohort Study. The American Journal of Medicine 2018 https://www.ncbi.nlm.nih.gov/pubmed/30056104
- Gu Y, Brickman AM, Stern Y, et al. Mediterranean diet and brain structure in a multiethnic elderly cohort. Neurology 2015;85 (20):1744–1751. https://www.ncbi.nlm.nih.gov/pubmed/26491085
- Mosconi L, Murray J, Tsui WH, et al. Mediterranean diet and magnetic resonance imaging-assessed brain atrophy in cognitively normal individuals at risk for Alzheimer’s disease. J Prev Alzheimers Dis. 2014;1(1):23–32.https://www.ncbi.nlm.nih.gov/pubmed/25237654
- Staubo SC, Aakre JA, Vemuri P, et al. Mediterranean diet, micronutrients and macronutrients, and MRI measures of cortical thickness. Alzheimers Dement. 2017;13(2):168-177. https://www.ncbi.nlm.nih.gov/pubmed/27461490
- Jacka, F.N, Cherbuin, N, Anstey, KJ et al. Western diet is associated with a smaller hippocampus:a longitudinal investigation. BMJ 2015; 13:215 https://www.ncbi.nlm.nih.gov/pubmed/26349802
- Stranahan AM, Norman ED, Lee K, et al. Diet-induced insulin resistance impairs hippocampal synaptic plasticity and cognition in middleaged rats. Hippocampus. 2008;18(11):1085–1088. https://www.ncbi.nlm.nih.gov/pubmed/18651634