Diet can impact cognitive aging, but comprehensive data from human studies is lacking and the underlying biological mechanisms are still not fully understood.

To investigate the associations between two dietary patterns consistently linked to inflammation and brain health [the Mediterranean diet (MDS) and inflammatory potential of diet (EDII)] and five blood-based biomarkers of Alzheimer´s disease (AD) in a sample of dementia-free community-dwelling older adults.

We used cross-sectional data from the Swedish National Study on Aging and Care in Kungsholmen (SNAC-K).

Participants who were institutionalized, had dementia or Parkinson's disease, or had missing data on diet and/or biomarkers were excluded. Our study sample consisted of 1907 adults ≥60 years old.

Adherence to the MDS and EDII was assessed using a validated food frequency questionnaire. T-tau, p-tau181, Aβ 42/40, NfL, and GFAP were measured in serum. Associations were estimated through quantile regression models at the 25th, 50th, and 75th percentiles of the biomarkers’ levels, and were adjusted for potential confounders and stratified by sex, age, and APOE-e4 genotype.

In the whole sample, higher adherence to the MDS was associated with lower levels of p-tau181 at the 50th and 75th percentiles [β (95% CI) per 1-SD increment = -0.028 (-0.053, -0.002) and -0.036 (-0.072, -0.001), respectively], while higher adherence to the EDII was associated with higher levels of NfL at the 75th percentile [β (95% CI) per 1-SD increment =0.031 (0.008, 0.053)]. Associations with other biomarkers were only apparent at lower levels of their distribution. Subgroup analyses showed: 1) a stronger inverse association between the MDS and p-tau181 in APOE-e4 carriers than non-carriers, and 2) an inverse association of the MDS with GFAP only in participants ≥78 years.

Diet seems to be associated with biomarkers of AD pathology in cognitively intact older adults. Some associations were more apparent in the presence of genetic predisposition for AD or advanced age.