Effect of FLAVAnols on bone turnover markers in type 2 diabetes mellitus–post hoc analysis from a 3-month randomized placebo-controlled trial

BACKGROUND: Individuals with type 2 diabetes mellitus (T2DM) have increased fracture risk with high bone mineral density, possibly related to advanced glycation end products (AGEs) accumulation in bone. Flavanol supplementation in postmenopausal women reduced AGEs formation and decreased bone resorption markers. However, to date, these effects have not been investigated in T2DM. OBJECTIVE: We used a post hoc secondary analysis to determine the effect of monomeric and oligomeric flavanols supplementation on bone turnover markers (BTMs) in individuals with T2DM. METHODS: Eighty-three individuals with T2DM, aged 40–85 years, with microalbuminuria were enrolled from 4 trial centers in Rotterdam, the Netherlands, into a randomized, double-blind, placebo-controlled trial with renal vascular health as the primary outcome. Participants were randomized (1:1) to receive either a placebo or 200 mg of monomeric and oligomeric flavanols as intervention for three months. Serum alkaline phosphatase (ALP), type I collagen crosslinked beta C-telopeptide (β-CTx), and type I procollagen-N-propeptide (P1NP) were measured at baseline and three months. ANCOVA was performed on rank transformed BTMs at three months as the outcome, adjusting for baseline BTMs, group, age, sex, and BMI. RESULTS: Baseline characteristics did not differ between the two arms. The adjusted mean change in BTMs at three months was not different between the placebo vs. intervention arm: ALP –0.059 (–0.262–0.145) vs. 0.060 (–0.135–0.356), p = 0.41; β-CTx 0.013 (–0.205–0.231) vs. 0.100 (–0.109–0.310), p = 0.53 and P1NP 0.091 (–0.080–0.262) vs. 0.030 (–0.134–0.195), p = 0.61. There was no significant within-group change in BTMs after three months in both study arms. CONCLUSION: Supplementation with daily 200 mg of flavanols during three months, on top of usual care in individuals with T2DM, did not result in changes in BTMs compared to placebo. Future studies are needed to show whether long-term supplementation in higher dosages may positively affect BTMs in individuals with T2DM.