Impact of Dietary Phosphate on Bone Health in Microgravity

Gravity is critical for maintaining healthy bones since it causes loads that lead to bone strengthening and remodelling, particularly in weight-bearing bones such as those of the lower limbs. In contrast, reduced loading—such as during spaceflight—leads to bone resorption and loss of structure. Phosphate in the diet also plays an essential role in bone metabolism; while adequate intake supports healthy bone growth, deficiency and excess both compromise bone quality. This study investigates the interaction between mechanical unloading and dietary phosphate level on bone strength in microgravity. A rat model is used for the experiment, with the choice made in terms of accepted research standards and the similarity of rats to humans in terms of comparable bone remodelling response. Three experimental groups are male, female, and ovariectomized (OVX) female rats, the latter of which simulates postmenopausal status with estrogen deficiency, which plays a role in bone resorption. These groups are further divided into hindlimb-loaded and unloaded, and normal and high phosphate diet. (12 groups in total) Previous study on bone volume fraction and bone mineral density under space-like simulation indicated that an increased phosphate diet aggravates the bone loss over usual phosphate consumption. As a follow-up to these experiments, mechanical testing through 4-point bend tests and Finite Element Analysis (FEA) are being conducted to quantify the flexural strength of the bones. This research aims to obtain insight into the interactive influences of mechanical unloading and diet on bone health, with relevance towards the establishment of effective nutritional countermeasures for spaceflight. All procedures were approved by Animal Ethics. Image 1: 4-Point Bend Fixture and bone setup.