Mediterranean and Western diet effects on Alzheimer's disease biomarkers, cerebral perfusion, and cognition in mid-life: A randomized trial

Introduction: Mid-life dietary patterns are associated with Alzheimer's disease (AD) risk, although few controlled trials have been conducted. Methods: Eighty-seven participants (age range: 45 to 65) with normal cognition (NC, n = 56) or mild cognitive impairment (MCI, n = 31) received isocaloric diets high or low in saturated fat, glycemic index, and sodium (Western-like/West-diet vs. Mediterranean-like/Med-diet) for 4 weeks. Diet effects on cerebrospinal fluid (CSF) biomarkers, cognition, and cerebral perfusion were assessed to determine whether responses differed by cognitive status. Results: CSF amyloid beta (Aβ)42/40 ratios increased following the Med-diet, and decreased after West-diet for NC adults, whereas the MCI group showed the reverse pattern. For the MCI group, the West-diet reduced and the Med-diet increased total tau (t-tau), whereas CSF Aβ42/t-tau ratios increased following the West-diet and decreased following the Med-diet. For NC participants, the Med-diet increased and the West-diet decreased cerebral perfusion. Discussion: Diet response during middle age may highlight early pathophysiological processes that increase AD risk.