Almonds and Their Impact on Mental Health and the Gut-Brain Axis in Adults with Symptoms of Anxiety and Depression: A 12-Week Randomized Controlled Trial.

BACKGROUND

Almonds contain dietary fiber, micronutrients, and phytochemicals that have been implicated in the regulation of the gut-brain axis and mental health.

OBJECTIVES

The aim of this study was to investigate the effect of whole almonds, compared with an isocaloric snack, on mental health and the gut-brain axis, in adults with symptoms of anxiety and depression.

METHODS

Adults with mild-to-moderate symptoms of anxiety and depression participated in a randomized controlled trial, receiving almonds (56 g/d) or isocaloric control for 12 wk. The primary outcome was symptoms of anxiety and depression (Patient Health Questionnaire Anxiety and Depression Scale) at week 12. Secondary mental health outcomes were measured at weeks 0, 6, and 12. Gut microbiota composition (16S rRNA gene sequencing), short-chain fatty acids (SCFAs; gas chromatography), stool output (frequency and consistency), and gut symptoms (7-d diary) were measured at weeks 0 and 12.

RESULTS

Eighty-four participants were recruited (mean age 25 y, 75% female). There was no significant difference in anxiety and depression scores between the almond (mean ± SD, 11.6 ± 5.3) and control group (12.5 ± 5.3; P = 0.945). Functional impairment was borderline significantly improved in the almond group (9.6 ± 7.0) compared with control (12.2 ± 8.7, P = 0.055) in the intention-to-treat analysis and was significant in the per-protocol analysis (almond 9.0 ± 6.4 compared with control 12.5 ± 9.6; P = 0.015). Almonds did not alter the gut microbiota composition or SCFA concentrations. Almonds significantly reduced the frequency of hard stools compared with control (median [interquartile range]: 0.0 [0.1] compared with 0.1 [0.4] stools/d, P = 0.002), with no impact on gut symptoms.

CONCLUSIONS

Almond consumption for 12 wk has limited impact on anxiety and depression, although it may impact functional impairment in adults with mild-to-moderate anxiety and depression. Further research is needed in populations with severe depression and anxiety. This trial was registered at clinicaltrials.gov as NCT06087471.