Western diet is associated with a smaller hippocampus: a longitudinal investigation

BACKGROUND Recent meta-analyses confirm a relationship between diet quality and both depression and cognitive health in adults. While the biological pathways that underpin these relationships are likely multitudinous, extensive evidence from animal studies points to the involvement of the hippocampus. The aim of this study was to examine the association between dietary patterns and hippocampal volume in humans, and to assess whether diet was associated with differential rates of hippocampal atrophy over time. METHODS Data were drawn from the Personality and Total Health Through Life Study and focused on a subsample of the cohort (n = 255) who were aged 60–64 years at baseline in 2001, completed a food frequency questionnaire, and underwent two magnetic resonance imaging scans approximately 4 years apart. Longitudinal generalized estimating equation linear regression models were used to assess the association between dietary factors and left and right hippocampal volumes over time. RESULTS Every one standard deviation increase in healthy “prudent” dietary pattern was associated with a 45.7 mm3 (standard error 22.9 mm3) larger left hippocampal volume, while higher consumption of an unhealthy “Western” dietary pattern was (independently) associated with a 52.6 mm3 (SE 26.6 mm3) smaller left hippocampal volume. These relationships were independent of covariates including age, gender, education, labour-force status, depressive symptoms and medication, physical activity, smoking, hypertension and diabetes. While hippocampal volume declined over time, there was no evidence that dietary patterns influenced this decline. No relationships were observed between dietary patterns and right hippocampal volume. CONCLUSIONS Lower intakes of nutrient-dense foods and higher intakes of unhealthy foods are each independently associated with smaller left hippocampal volume. To our knowledge, this is the first human study to demonstrate associations between diet and hippocampal volume concordant with data previously observed in animal models.FNJ is funded by Deakin University and has received Grant/Research support from the Brain and Behaviour Research Institute, the National Health and Medical Research Council (NHMRC), Australian Rotary Health, the Geelong Medical Research Foundation, the Ian Potter Foundation, Eli Lilly, the Meat and Livestock Board and The University of Melbourne and has received speakers’ honoraria from Sanofi-Synthelabo, Janssen Cilag, Servier, Pfizer, Health Ed, Network Nutrition, Angelini Farmaceutica, and Eli Lilly. KJA is funded by NHMRC Research Fellowship No. 1002560. NC is funded by an ARC Future Fellowship No. 120100227. PB is funded by an ARC Future Fellowship # FT130101444. The PATH study was supported by NHMRC Grants No. 973302, Program Grants No. 179805 and 350833, and NHMRC project grant No. 157125 and 1063907