Low Calcium and High Fructose Diet Diminish the Quality of Circumferential Long-Bone Growth

High fructose (HF) intake is a public health problem. However, little is known about effects on bone quality during growth. Greater data exists for low calcium (Ca²⁺). Low-Ca (0.02%) or normal calcium and calorie-equivalent glucose or fructose diets (43%) were fed to male, 3-wk-old, B6 mice for 6 wks (4 groups; n=9/group). Weight and long-bone lengths were not affected. Low-Ca diet resulted in less stiff and strong (~40%; p<;0.01) long bone and increased toughness (energy absorption) of long-bone mid-shaft, measured by 3-point bending; post-yield displacement was increased in low Ca by >65% (p<;0.05). By histomorphometry, low Ca resulted in decreased (>20%, p<;0.05) cortical width, partially explaining the bending results. Only the glucose-fed group exhibited compensation to maintain outside circumference and diameter by increased periosteal bone formation rate (p.BFR); 3-fold greater vs. each of the other 3 groups (p<;0.05). One plausible mechanism for poor circumferential growth involves bone in a feedback loop and is suggested by decreased intestinal Ca transport and Ca transporter protein in mucosa. The fructose diet completely prevented both adaptive increases in Ca transport, and 1α-hydroxylase-mediated synthesis of 1,25(OH)₂D₃ levels.