# Association Between the Dutch Mediterranean‐Dietary Approaches to Stop Hypertension Intervention for Neurodegenerative Delay (MIND‐NL) Diet Adherence and Systemic Tryptophan Metabolites in Older Adults at Risk of Cognitive Decline: An Exploratory Study

## TL;DR

Following the MIND diet may improve brain health in older adults at risk of cognitive decline by altering tryptophan metabolism.

## Contribution

This study explores how adherence to the MIND diet affects systemic tryptophan metabolites linked to neurodegeneration.

## Key findings

- Greater MIND diet adherence was associated with lower quinolinic acid levels.
- Diet adherence was linked to reduced kynurenine:tryptophan ratios.
- Diet changes inversely correlated with kynurenine:large neutral amino acids ratios.

## Abstract

Tryptophan (TRP) metabolism is emerging as a focus of investigation in Alzheimer's disease research. In addition, diet might impact TRP's metabolic fate. The aim of this study was to explore the association between adherence to the Dutch Mediterranean‐Dietary Approaches to Stop Hypertension (DASH) Intervention for Neurodegenerative Delay (MIND‐NL) diet and systemic TRP metabolite levels and their related ratios in older adults at risk of cognitive decline. Data of the HELI multidomain lifestyle intervention study (n = 82) were used. Dietary intake data (FFQ) and fasted plasma levels were collected at baseline and 26 weeks follow‐up. Bivariate Latent Change Score Models (LCSMs) were applied to assess both level‐level and change‐change associations, adjusted for lifestyle factors. Changes in MIND‐NL diet adherence were significantly inversely associated with changes in the kynurenine:large neutral amino acids ratio (path coefficient −0.457, SE:0.206, p = 0.03) and kynurenine:tryptophan ratio (path coefficient −0.558 SE:0.235, p = 0.02). In addition, MIND‐NL diet adherence was associated with lower levels of the neurotoxic metabolite quinolinic acid (path coefficient −0.186, SE:0.0700, p = 0.008), but within the crude model only. Our findings suggest that greater adherence to the MIND‐NL diet may contribute to decreased activation of the kynurenine pathway.

Following the MIND diet may support brain health in older adults at risk of cognitive decline by influencing tryptophan (TRP) metabolism. Plasma samples and dietary intake data from the HELI intervention trial were used. Bivariate latent change score modeling analysis showed that greater adherence to the MIND diet was linked to higher tryptophan levels, lower levels of quinolinic acid, a harmful neurotoxic metabolite, and lower levels of the kynurenine/TRP ratio. This suggests the diet reduces activation of the kynurenine pathway, involved in neurodegeneration.