The relationship between 25-hydroxyvitamin D and markers of intestinal and systemic inflammation in undernourished and non-undernourished children, 6–59 months.

• In undernourished children: serum 25(OH)D associated negatively with FGF-21. • In undernourished children: vitamin D sufficiency [25(OH)D ≥ 30 ng/mL] associated with lower FGF-21. • In undernourished children: vitamin D supplementation reduced TNF-α by 65% • Vitamin D sufficiency [serum 25(OH)D ≥ 30 ng/mL] associated with lower IFABP in non-undernourished children. Elevated inflammation contributes to growth faltering in children. Vitamin D (vitD) suppresses pro-inflammatory and enhances anti-inflammatory molecule production, thus vitamin D deficiency (VDD) has been associated with heightened inflammation. In undernourished children, VDD and inflammation co-exist, however, little is known about their interaction. This cross-sectional study aimed to investigate the association of serum 25-hydroxyvitamin D (25(OH)D) concentration with markers of inflammation in undernourished and non-undernourished children, as well as the effect of vitD supplementation on inflammatory markers in the children with low 25(OH)D in a nested before-and-after trial. Serum 25(OH)D, IL-1β, IL-8, IL-10, TNF-α, CRP, AGP, IFABP, sCD14, IGF-1 and FGF-21 of 121 undernourished and 51 non-undernourished children aged 6–59 months were measured cross-sectionally. Children with serum 25(OH)D < 30 ng/mL received 50,000 IU/week of vitD for three weeks. TNF-α and FGF-21 in the overall and undernourished group were higher in those with serum 25(OH)D < 30 ng/mL compared to those with serum ≥ 30 ng/mL (p < 0.05), while IFABP concentration was higher in the non-undernourished children with serum 25(OH)D < 30 ng/mL (p = 0.047). Serum 25(OH)D was negatively associated with TNF-α in the overall group (β = −0.012, p = 0.034); and FGF-21 (β = −0.013, p = 0.023) in the undernourished group. After the supplementation trial, TNF-α was reduced by 55.9 % (p = 0.008) and 64.7 % (p = 0.017) in the overall and undernourished groups respectively, and AGP showed a trend of 41.6 % reduction (p = 0.099) in the overall group. IL-1β concentration increased post-supplementation in the overall (p = 0.011) and undernourished groups (p = 0.039). Optimising vitD status may potentially be a strategy for reducing systemic and gut inflammation, and subsequently improving growth, particularly in undernourished children. [ABSTRACT FROM AUTHOR]