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Almonds and the optimization of immune responses to influenza vaccination, compared to a control snack, in healthy
Alice van der Schoot1, Alice C Creedon1, Noa Argomaniz1
1Department of Nutritional Sciences, King's College London, London, UK.
Background:
Certain nutrient supplements enhance immune responses to vaccination; however, no randomized controlled trials (RCTs) have assessed the impact of a whole food. Almonds may benefit immune function through immunoregulatory nutrients and fiber, which interacts with the immune system via the gut microbiota.
Objective:
This study assessed the effect of almonds on the immune response following influenza vaccination, compared to an isocaloric snack, in healthy adults.
Methods:
In this RCT, healthy adults (40-64 years) consumed almonds (56 g/d) or an isocaloric control (86 g/d pretzels) for 8 weeks. Participants received seasonal influenza vaccine at week 4. The primary outcome was seroconversion rates for ≥1 strain at week 8. Antigen-specific antibody titers (HI assay) were quantified pre- (week 4) and post-vaccination (week 8), and seroconversion and seroprotection were calculated. The gut microbiota, short-chain fatty acids (SCFAs), stool output and gut symptoms were measured at baseline, midpoint and endpoint.
Results:
Ninety participants were randomized (mean age 51 years, 73% females). Seroconversion rate for ≥1 strain was high and not significantly different between groups [almond: 38/41 (93%) versus control: 37/39 (95%), P=1.000], nor were strain-specific seroconversion or seroprotection rates. Almonds resulted in higher antibody titers for A/Wisconsin/67/2022 (H1N1) strain, compared to control [geometric mean (95% CI): almond 359 (146, 881) versus control 110 (51, 235)], and greater fold-change for A/Wisconsin/67/2022 (H1N1) [geometric mean fold change (95% CI): almond 18 (7, 48) versus control 4 (3, 7)] and B/Yamagata [almond 10 (6, 16) versus control 5 (3, 7)]. Absolute abundance of Roseburia hominis was significantly higher in the almond group compared to control (q=0.049). There was no effect on SCFAs or stool consistency.
Conclusions:
Almonds increased influenza vaccine antibody titers but did not affect seroconversion in a healthy population where vaccines are already highly effective. This trial was pre-registered at clinicaltrials.gov as NCT05515263 (https://clinicaltrials.gov/study/NCT05515263).
