Bone Turnover Markers (CTX and P1NP) Following Low-Carbohydrate and Mediterranean Diet Interventions in Adolescents and Young Adults with Type 1 Diabetes

Background: Impaired bone health is a recognized complication of type 1 diabetes. This study evaluated the effects of low-carbohydrate (LC) and Mediterranean (MED) diets on bone turnover markers in adolescents and young adults. Methods: In a 24-week randomized controlled trial, 40 individuals aged 12–21 years, with type 1 diabetes, were assigned to an LC or MED intervention (20 participants per group). C-terminal telopeptide (CTX) and procollagen type 1 N-terminal propeptide (P1NP) were measured at baseline and 24 weeks. Results: The groups had similar baselines. At 24 weeks, the between-group difference in delta glucose time in range was not statistically significant; median daily carbohydrate intake was 86 g (68–95) in LC and 130 g (102–173) in MED (p < 0.001). Comparing LC to MED, the median BMI z-score was lower (−0.1 [−0.3 to −0.1] vs. 0.0 [−0.1 to −0.1], p = 0.10), and calcium (p = 0.035) and magnesium intakes (p = 0.030) were lower. These associations did not remain statistically significant after false-discovery-rate correction. The median-adjusted alkaline phosphatase level decreased significantly in the LC group (p = 0.009). The median CTX changed following LC from 395 pg/mL (232–591) to 423 pg/mL (289–591) (p = 0.278); and following MED, from 357 pg/mL (244–782) to 296 pg/mL (227–661) (p = 0.245). P1NP changed in LC from 95 ng/mL (68–112) to 88 ng/mL (62–97) (p = 0.056) and in MED from 76 ng/mL (54–198) to 71 ng/mL (55–122) (p = 0.594). Conclusions: Exploratory analyses of bone turnover markers showed insignificant differences following LC and MED diets.