Mixed Nuts as Healthy Snacks: Effect on Tryptophan Metabolism and Cardiovascular Risk Factors

Area of Science:

• Nutritional Science
• Metabolic Health
• Gut Microbiome Research

Background:

• Mixed tree nuts (MTNs) consumption during caloric restriction is linked to reduced cardiovascular risk factors and increased satiety.
• Tryptophan (Trp) metabolism is implicated in cardiovascular disease (CVD) pathogenesis.
• The impact of MTNs on Trp metabolism and its connection to CVD risk markers requires further investigation.

Purpose of the Study:

• To investigate the effect of daily mixed tree nut (MTN) consumption on tryptophan (Trp) metabolism.
• To explore the association between MTN-altered Trp metabolism and cardiovascular risk markers.
• To examine changes in the gut microbiota in response to MTN consumption.

Main Methods:

• A 12-week hypocaloric diet with daily MTNs or pretzels, followed by 12 weeks of isocaloric maintenance.
• Plasma and fecal samples analyzed for Trp metabolites using LC-MS.
• Gut microbiota composition assessed via 16S rRNA sequencing.

Main Results:

• Trp-kynurenine metabolism decreased in the MTNs group during the weight loss phase.
• Trp-serotonin and Trp-indole metabolism increased from baseline in the MTNs group compared to the pretzel group.
• While overall microbial diversity showed no significant changes, the relative abundance of the genus *Paludicola* differed significantly between groups.

Conclusions:

• Mixed tree nut consumption influences host and microbial tryptophan metabolism in overweight and obese individuals.
• Alterations in Trp metabolism pathways are associated with MTN intake.
• Specific gut microbial changes, particularly in *Paludicola*, may mediate some effects of MTNs on metabolism.