Partial Replacement of Animal Proteins with Plant Proteins for 12 Weeks Accelerates Bone Turnover Among Healthy Adults: A Randomized Clinical Trial

BACKGROUND Plant-based diets may reduce the risk of chronic diseases, but can also lead to low calcium and vitamin D intakes, posing a risk for bone health. OBJECTIVES We investigated whether partial replacement of animal proteins with plant-based proteins using a whole-diet approach affects bone and mineral metabolism in healthy adults in 3 groups fed diets differing in protein composition. METHODS This 12-week clinical trial was comprised of 107 women and 29 men (20-69 years old; BMI mean ± SD, 24.8 ± 3.9) randomly assigned to consume 1 of 3 diets designed to provide 17 energy percent (E%) protein: "animal" (70% animal protein, 30% plant protein of total protein intake), "50/50" (50% animal, 50% plant), and "plant" (30% animal, 70% plant) diets. We examined differences in bone formation [serum intact procollagen type I amino-terminal propeptide (S-iPINP)], bone resorption [serum collagen type 1 cross-linked C-terminal telopeptide (S-CTX)], mineral metabolism markers (primary outcomes), and nutrient intakes (secondary outcomes) by ANOVA/ANCOVA. RESULTS S-CTX was significantly higher in the plant group (mean ± SEM, 0.44 ± 0.02 ng/mL) than in the other groups (P values