Mixed Tree Nuts, Cognition and Gut Microbiota: a 4-week, Placebo-Controlled, Randomized Crossover Trial in Healthy Non-Elderly Adults

Crystal F Haskell-Ramsay*, Fiona L Dodd, Darren Smith, Lewis Cuthbertson, Andrew Nelson, John K Lodge, Philippa A Jackson

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Background
Beneficial effects of nut supplementation on cognitive function have previously been demonstrated in young and older adults. Alterations to gut microbiota have also been shown following tree nut consumption. However, no data exists on the effects of nuts on cognition and intestinal microbial communities assessed within the same study.

Objectives
The study aimed to examine the effects of daily consumption of tree nuts for 4 wk on cognitive function (primary outcome), mood, metabolomics, and gut microbial species (secondary outcomes) in healthy, nonelderly adults.

Methods
This randomized, placebo-controlled, double-blind, counterbalanced crossover study assessed the effects of 4 wk of supplementation with 30 g/d mixed tree nuts versus placebo on cognition and mood in 79 healthy adults aged 18–49 y. Metabolic responses, gut bacterial community structure, and the potential for these to impact cognition were explored using a multi-omic approach. Bacterial community analysis was conducted in Quantitative Insights Into Microbial Ecology 2 (QIIME2).

Results
Mixed model analysis indicated that nut consumption led to significant improvements to accuracy (placebo M = 92.2% compared with NUTS M = 94.5%; P = 0.019) and speed of response (placebo M = 788 ms compared with NUTS M = 757 ms; P = 0.004) on a picture recognition task. No significant changes to bacterial community α or β diversity were observed when comparing nut consumption to the placebo arm. However, an unclassified Lachnospiraceae amplicon sequence variant (ASV) was significantly enriched in participants when supplemented with nuts (P = 0.015). No correlations were observed between the changes to picture recognition and the changes to the unclassified Lachnospiraceae ASV. There were no significant changes to the urinary metabolome.

Conclusions
These findings indicate a positive effect of nut on cognition following only 4 wk of consumption in a healthy nonelderly sample, as well as upregulation of a microbial taxa associated with gut health. The effects appear to be independent of one another, but further exploration is required in those experiencing cognitive decline and/or gut dysbiosis.

The study was registered at clinicaltrials.gov (identifier: NCT03500601).
Original languageEnglish
Article numbernxac228
Pages (from-to)1-11
Number of pages11
JournalThe Journal of Nutrition
Early online date6 Oct 2022
DOIs
Publication statusE-pub ahead of print - 6 Oct 2022

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