Dietary sodium as a risk factor for osteoporosis: where is the evidence?
Na-induced calciuria has been well documented and provides a physiological basis for the proposed role of dietary Na (or salt) as a risk factor for osteoporosis. However, the evidence is based primarily on acute salt-loading studies, and there are insufficient data on the effects of high salt intake on net Ca retention to predict long-term effects on bone health. Results of investigations on salt and bone turnover, as assessed by bone biomarkers, are inconsistent, but the large variations in inter-individual response to acute and chronic Na loading may be related to salt sensitivity. Results of cross-sectional and prospective investigations on high salt intake and long-term bone health are inconclusive, probably reflecting the difficulty of conducting such studies in free-living populations. However, the mean urinary Ca loss of 1 mmol/100 mmol Na suggests that chronic changes in salt intake may have large effects on Ca and bone balance, especially in individuals with a reduced capacity to compensate for Na-induced Ca loss. Investigating the relationship between salt intake and bone health requires a greater focus on whole diets (including components such as K, Mg, P and protein), reliable measures of salt intake, appropriate bone health outcome measures, and improved subject characterisation (e.g. salt sensitivity). The reasons for inter-individual variability should be explored using post-genomic techniques.
Teucher
Birgit
B
Nutrition Division, Institute of Food Research, Norwich NR4 7UA, UK. birgit.teucher@bbsrc.ac.uk
Fairweather-Tait
Sue
S
D015519:Bone Density / Q000502:physiology; D001842:Bone and Bones / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism* / Q000652:urine; D006801:Humans; D006967:Hypersensitivity; D010024:Osteoporosis / Q000209:etiology*; D012307:Risk Factors; D012982:Sodium, Dietary / Q000008:administration & dosage / Q000009:adverse effects*
D012982:Sodium, Dietary; D002118:Calcium