A 7-week reduction in salt intake does not contribute to markers of bone metabolism in young healthy subjects.
BACKGROUND
Sodium intake increases urinary calcium excretion and may thus lead to negative calcium balance and bone loss.


OBJECTIVE
We hypothesised that reducing sodium intake would reduce urinary calcium excretion and have a beneficial influence in bone metabolism.


METHODS
A total of 29 subjects, 14 males and 15 females, were divided into two study groups. One group (low-sodium group (LS)) reduced sodium intake for 7 weeks by substituting low-salt alternatives for the most important dietary sources of sodium. The other group, serving as a control group (C), was given the same food items in the form of normally salted alternatives. Fasting serum samples as well as 24-h urine samples were obtained in the beginning and at the end of the study. Urinary sodium, urinary calcium, urinary creatinine, serum calcium, serum phosphate, serum creatinine, serum parathyroid hormone (s-PTH), serum C-terminal telopeptides of Type-I collagen and serum bone alkaline phosphatase (s-B-ALP) were analysed.


RESULTS
The LS group showed a significant decline (P = 0.001) in urinary sodium/creatinine ratio without a significant effect on urinary calcium/creatinine ratio. In the LS group, s-PTH increased (P = 0.03). The C group showed an increase in s-PTH (P = 0.05) and in s-B-ALP, but no differences were observed between the study groups in the changes of serum markers of calcium and bone metabolism.


CONCLUSIONS
We have shown that reducing the sodium intake of young, healthy people with adequate calcium intake over a 7-week period does not affect the markers of bone metabolism.
Natri
A-M
AM
Department of Applied Chemistry and Microbiology, Division of Nutrition, University of Helsinki, Finland.
Kärkkäinen
M U M
MU
Ruusunen
M
M
Puolanne
E
E
Lamberg-Allardt
C
C
D000328:Adult; D000469:Alkaline Phosphatase / Q000097:blood*; D015415:Biomarkers / Q000097:blood / Q000652:urine; D001842:Bone and Bones / Q000378:metabolism*; D002118:Calcium / Q000097:blood / Q000652:urine*; D003404:Creatinine / Q000652:urine; D004039:Diet, Sodium-Restricted; D005260:Female; D006801:Humans; D008297:Male; D010281:Parathyroid Hormone / Q000097:blood; D012964:Sodium / Q000652:urine; D017673:Sodium Chloride, Dietary / Q000008:administration & dosage*
D015415:Biomarkers; D010281:Parathyroid Hormone; D017673:Sodium Chloride, Dietary; D012964:Sodium; D003404:Creatinine; D000469:Alkaline Phosphatase; D002118:Calcium