Urinary calcium, sodium, and bone mass of young females

Abstract

Calcium is an important determinant of peak bone mass in young adults because of its influence on skeletal development during growth. Attainment of maximum peak bone mass requires optimal positive balance between calcium intake and obligatory losses of calcium, primarily in urine and feces. Urinary excretion is an important determinant of calcium retention in the body. Accordingly, the purpose of this study was to evaluate the influence of various nutrients on urinary calcium excretion, and to assess their impact on bone mass of young females, aged 8-13 y, during early puberty. The study was conducted in 381 healthy white females in pubertal stage 2. From each participant we collected basic anthropometric measurements, a 3-d food record, blood, a 24-h urine sample, and bone mass measurements of the total body and forearm by dual X-ray absorptiometry. Urinary sodium was found to be one of the most important determinants of urinary calcium excretion: [urinary calcium (mmol/d) = 0.01154 x urinary sodium (mmol/d) + 0.823], whereas calcium intake had relatively little impact: [urinary calcium (mmol/d) = 0.02252 x calcium intake (mmol/d) + 1.5261]. Urinary calcium was much higher at a calcium intake of approximately 37.5 mmol/d (1500 mg/d), supporting the notion that calcium is a threshold nutrient. Calcium intake had a significant positive influence on the bone mineral content and density of the whole body and radius shaft whereas urinary calcium had a negative influence, presumably by reducing calcium accretion into the skeleton.(ABSTRACT TRUNCATED AT 250 WORDS)

Prevalence of iodine inadequacy in Switzerland assessed by the estimated average requirement cut-point method in relation to the impact of iodized salt

“…In adults, Ca intake can be associated with urinary Ca excretion (42) . Milk as part of the everyday diet contains high Ca levels and is also a major source of iodine (43) .…”

A 7-week reduction in salt intake does not contribute to markers of bone metabolism in young healthy subjects

“…It was concluded that no bone loss occurs when urinary sodium excretion is less than 92 mmol/day. In other population studies, no association between sodium and bone density has been found, but sodium intake has been assessed by a single urine specimen (Matkovic et al, 1995;DawsonHughes et al, 1996;Jones et al, 1997Jones et al, , 2001Carbone et al, 2003) or by a dietary recall (Greendale et al, 1994).…”

“…A commonly suggested strategy to diminish bone loss is to maintain positive calcium balance by consuming a diet containing adequate amounts of calcium and vitamin D. The positive relationship between urinary sodium and calcium excretion in humans has been established previously in both cross-sectional (Goulding, 1981;Law et al, 1988;Shortt et al, 1988;Chan et al, 1992;Matkovic et al, 1995;Dawson-Hughes et al, 1996;Itoh & Suyama, 1996;O'Brien et al, 1996;Jones et al, 1997) and experimental studies (Breslau et al, 1982;Goulding & Lim, 1983;Castenmiller et al, 1985;Law et al, 1988;McParland et al, 1989;Zarkadas et al, 1989;Chan et al, 1992;Evans et al, 1997). It could be hypothesised that sodium-induced urinary calcium loss decreases serum calcium concentration, which is compensated for increased excretion of parathyroid hormone (PTH) from the parathyroid glands (Evans et al, 1997).…”

A population-based study of the relationship between salt intake, bone resorption and bone mass

“…Urinary sodium also correlates with older less speci®c markers of bone resorption suggesting a possible impact on bone mass (McParland et al, 1989;Need et al, 1991). Clinical studies in humans relating salt intake to bone mass have been relatively few and contradictory (Nordin & Polley, 1987;Devine et al, 1995;Matkovic et al, 1995;Greendale et al, 1994). Two studies (Nordine, & Polley, 1987;Devine et al, 1995) found weak but signi®cant correlations between urinary sodium excretion and bone mass while two others (Matkovic et al, 1995;Greendale et al, 1994) found no association.…”

“…Clinical studies in humans relating salt intake to bone mass have been relatively few and contradictory (Nordin & Polley, 1987;Devine et al, 1995;Matkovic et al, 1995;Greendale et al, 1994). Two studies (Nordine, & Polley, 1987;Devine et al, 1995) found weak but signi®cant correlations between urinary sodium excretion and bone mass while two others (Matkovic et al, 1995;Greendale et al, 1994) found no association. There have been no studies in males and most have involved highly selected subjects.…”