Modeling how iso-caloric macronutrient substitutions are longitudinally associated with plasma kynurenines in colorectal cancer survivors up to 12 months posttreatment

Dietary intake of several macronutrients is associated with plasma kynurenines after colorectal cancer (CRC), and kynurenines have been linked to health-related outcomes. It is unknown how macronutrient substitution affects plasma kynurenines, which may be relevant for developing guidelines to improve post-CRC quality of life through dietary changes. Using iso-caloric substitution models, we investigated how substituting one macronutrient with another is longitudinally associated with plasma tryptophan, kynurenines, and kynurenine ratios in CRC survivors. Measurements were performed at 6-weeks, 6-months, and 12-months post-treatment in 247 stage I–III CRC survivors. Macronutrient intake was measured by 7-d dietary records and plasma kynurenines by LC/MS-MS. For analysis, we applied linear mixed models with false discovery rate (FDR) to adjust for multiple testing. After FDR adjustment, substituting 100 kcal/d of total carbohydrates with 100 kcal/d of total protein was associated with higher plasma concentrations of kynurenic acid (KA), xanthurenic acid (XA), and a higher kynurenic acid-to-quinolinic acid (KA/QA) ratio. Substituting 100 kcal/d of total carbohydrates with 100 kcal/d of total fat was associated with higher tryptophan concentrations, higher KA/QA ratio, and a lower kynurenine-to-tryptophan ratio (KTR) and hydroxykynurenine ratio (HKr). Substituting 100 kcal/d of total fat with 100 kcal/d of total protein was associated with higher XA concentrations. Altogether, iso-caloric macronutrient substitutions, particularly substituting carbohydrates with protein or fat, were longitudinally associated with higher concentrations of potentially favourable kynurenines and ratios (i.e., KA, XA, and KA/QA ratio) and lower ratios with pro-inflammatory or neurotoxic properties (i.e., KTR and HKr) in CRC survivors up to 12-months post-treatment.