# The association of essential dietary trace elements and their mixture with cognition: a prospective study

## TL;DR

This study explores how specific trace elements in the diet, like iron and zinc, are linked to cognitive function, finding non-linear relationships and sex differences.

## Contribution

The study identifies non-linear associations and sex-specific roles of dietary trace elements in cognition using a large prospective cohort.

## Key findings

- Non-linear associations between individual dietary trace elements and cognition were observed with specific inflection points.
- A mixture of trace elements showed an inverted 'U'-shaped relationship with cognition, with iron and zinc as key contributors.
- Sex differences were found, with manganese in males and zinc in females being the main contributors to cognition.

## Abstract

The association of dietary essential trace elements (ETEs) and their mixture with cognition remains unclear.

Prospective cohort data on the association between dietary ETEs [e.g., iron (Fe), copper (Cu), zinc (Zn), manganese (Mn), selenium (Se), and iodine (I)] and general cognition were obtained from the UK Biobank (UKB) database. Linear regression and restricted cubic splines (RCS) were used to examine the association between individual dietary ETEs and general cognition, including the identification of the inflection points. The Bayesian kernel machine regression (BKMR) model was applied to analyze the association between a mixture of six ETEs and general cognition, as well as potential interactions among ETEs. Stratified analysis and sensitivity analysis were also conducted.

Significant non-linear association between individual dietary ETEs and general cognition was observed, with the inflection points for the various elements being as follows: Fe: 15 mg/day, Zn: 10 mg/day, Cu: 1.5 mg/day, I: 250 μg/day, Mn: 5 mg/day, and Se: 45 μg/day. The BKMR analysis showed an inverted “U”-shaped association between dietary ETE mixture and general cognition, with Fe and Zn playing major roles. Dietary Mn was the major contributor in males, while Zn was predominant in females. In the hypertensive population, dietary Zn and Mn play major roles.

There are non-linear associations between dietary Fe, Zn, Cu, I, Mn, Se—as well as their mixture—and general cognition. Among these, Fe and Zn play major roles within this mixture. In addition, there are sex differences in the main contributing ETE, with Mn in males and Zn in females.