Frassetto & Sebastian (1996) emphasize how the day-to-day stability of acid base balance is highly dependent on the kidneys ability to excrete acid. They tried to obtain data on whether there was an increasing metabolic acidosis with age by doing an extensive literature review. While notably rather old, what the data showed was in fact that there was a significant increase in the steady state of blood H+ ion and a reduction in steady state HCO3-, both indicative of a progressively increasing low-level metabolic acidosis. They also noted a decrease in PaCO2, suggesting some long-term respiratory compensation. In women, there was less increase in H+ ion but greater decrease in PCO2, which the authors felt may indicate greater respiratory compensation. Is this important clinically? Well, based on hypotheses that, secondary to on going production of acid through metabolism, bone loses calcium to buffer the impact, the increasing metabolic acidosis, while not outside of normal pH range, could contribute to the occurrence of osteoporosis--and in fact some studies have been done attempting to alkalinize the blood in an effort to preserve bone with some positive impact (Sebastian, Harris, Ottaway, Todd, & Morris, 1994).