Background/Objectives: In vitro studies demonstrate that bone is degraded in an acidic environment due to chemical reactions and through effects on bone cells. Clinical evidence is insufficient to unequivocally resolve whether the diet net acid or base load bone affects breakdown in humans. Increasing dietary salt (sodium chloride, NaCl) mildly increases blood acidity in humans and in rats with increased sensitivity to the blood pressure effects of salt, whereas increased potassium (K) intake can decrease blood pressure. Blood pressure responses to NaCl or K may potentially be a marker for increased bone turnover or lower bone mineral density (BMD) in women at higher risk for osteoporosis and fracture.Subjects/Methods:We retrospectively analysed data from two data sets (California and NE Scotland) of postmenopausal women (n=266) enrolled in long-term randomized, placebo-controlled studies of the effects of administration of low-or high-dose dietary K alkali supplementation on bone turnover in relation to sodium or chloride excretion (a marker of dietary salt intake). Mean arterial pressure (MAP) was calculated from blood pressure measures, MAP was divided into tertiles and its influence on the effect of dietary NaCl and K alkali supplementation on deoxypyridinoline markers of bone resorption and BMD by DEXA was tested. Data was analysed for each data set separately and then combined.Results:Percentage change in BMD after 24 months was less for California compared with North East Scotland (hip: 0.6±2.8% and 1.5±2.4%, respectively (P=0.027); spine: 0.5±3.4% and 2.6±3.5%, (P0.001). We found no effect of dietary alkali treatment on BMD change or bone resorption for either centre. Adjusting for the possible calcium-or potassium-lowering effects on blood pressure did not alter the results.Conclusions:Blood pressure responses to Na, Cl or K intake did not help predict a BMD response to diet alkali therapy.
Bibliographical noteThis work was funded in part by the UK Food Standards Agency (UK) and in part by Armand Hammer (USA).
- blood pressure
- sodium chloride