Sustained and reversible effects of a dietary phosphate intake on bone and mineral metabolism during aging

The loss of bone volume during aging is common in both men and women and can have substantial negative health impacts. Weakened bones can lead to fractures which in turn can result in hospitalization, decreased quality of life, and early death. The post-diagnosis treatment of osteoporosis has received the bulk of attention with less research focused on prevention and modifiable risk factors such as nutrition. Calcium and vitamin D supplementation has provided limited skeletal benefit in healthy individuals and there is no currently sufficient information on other components of the diet for informed dietary choices related to bone health. Inorganic phosphate (Pi) is a dietary element that is consumed in excess in most Western diets and has been suggested to strongly influence bone metabolism. However, how duration of dietary Pi choices, stage of life, and gender influence the impact on long-term bone health is lacking. To address these issues, young (10 week) and old (82 week) male mice were fed low, normal, or high Pi content diets with calcium kept constant at 0.6% for 10 weeks and bone indices and Pi-responsive serum factors were measured. To determine if changes in bone quality in response to changes in dietary Pi were chronic or could be reversed, additional groups of mice were fed low or high Pi diets for 10 weeks and switched back to normal Pi for the final 10 weeks. A low-Pi additive diet produced a significant increase in trabecular and cortical bone volume in both young and old male mice. The high Pi diet generated trabecular bone loss in young mice which was not reversible by switching back to a normal Pi diet. The high Pi diet also induced accelerated loss of cortical bone and kidney calcification in old mice. Taken together, the results suggest that dietary choices made early in life could have long-term consequences on bone health and identify a novel non-pharmacologic, modifiable nutritional choice, in a low-Pi additive diet that could be used to build bone mass and/or prevent bone loss in the elderly.