The Effects of Refined Carbohydrates on Systemic Immunity: Results from a Randomized Controlled Feeding Trial

Objective To explore the effects of three diets differing in amount and type of refined carbohydrates on peripheral immunity. Methods After a weight loss of 15% with a very low carbohydrate diet (VLCD), participants were randomized to isocaloric diets: VLCD diet; high carbohydrate diet with high starch content (HC-Starch); or high carbohydrate diet with high sugar content (HC-Sugar). Changes in peripheral immunity were assessed using a multimodal analyses before randomization and after 10 weeks of diet. Results Multiplexed cytokine analysis shows increased adipsin in HC-Starch and decreased adiponectin in HC-Sugar. Transcriptomics analysis shows upregulation of immune and metabolic pathways with HC-Starch, but reductions with HC-Sugar. CyTOF revealed significant shifts in NK cell populations and increased inflammatory markers in neutrophils and monocytes following consumption of HC-Starch. Conclusions Consumption of refined starch following weight loss on a VLCD increases circulating markers of immune activity, whereas sugar consumption reduces these markers. Keywords: dietary nutrients, immunity, refined starch, added sugar, VLCD, cytokines, gene expression, CyTOF, inflammation, immune cells. ClinicalTrials.gov registration: NCT03394664