Association between urinary potassium, urinary sodium, current diet, and bone density in prepubertal children.
BACKGROUND
Our understanding of the role of nutrients in bone development in children is limited.


OBJECTIVE
We examined the associations between urinary potassium, urinary sodium, usual dietary intake, and bone mineral density (BMD) in prepubertal children.


METHODS
This was a cross-sectional study of 330 boys and girls aged 8 y. Urinary measures were assessed in a single, timed, overnight urine specimen. Usual diet was assessed with a food-frequency questionnaire completed by a parent or guardian. BMD at the femoral neck, lumbar spine, and total body was measured by dual-energy X-ray absorptiometry.


RESULTS
Urinary potassium correlated significantly with BMD at all sites (femoral neck: r = 0.20, P < 0.001; lumbar spine: r = 0.19, P = 0.001; total body: r = 0.24, P < 0.001). After adjustment for confounders (primarily lean body mass), this association was lower in magnitude but remained significant at 2 sites with a consistent trend at the third (femoral neck: P = 0.15; lumbar spine: P = 0.046; total body: P = 0.028). Urinary sodium was not associated with BMD at any site. No nutrient or food intake estimate was associated with BMD, although urinary potassium correlated significantly with potassium intake (r = 0.14, P = 0.016) and fruit and vegetable intake (r = 0.12, P = 0.033).


CONCLUSIONS
Urinary potassium was associated with both dietary intake and BMD independent of lean body mass in these well-nourished, calcium-replete young children. These findings should be confirmed in further longitudinal studies. Nevertheless, this association is likely to represent dietary intake of potassium and suggests that measurement of urinary potassium is superior to food-frequency questionnaires for assessing potassium intake in this age group.
Jones
G
G
Menzies Centre for Population Health Research, Hobart, Australia, and the College of Pharmacy and Nutrition, University of Saskatchewan, Saskatoon, Canada. g.jones@utas.edu.au
Riley
M D
MD
Whiting
S
S
D015502:Absorptiometry, Photon; D015415:Biomarkers / Q000652:urine; D015519:Bone Density; D001846:Bone Development / Q000502:physiology*; D001842:Bone and Bones / Q000378:metabolism*; D002648:Child; D003430:Cross-Sectional Studies; D004032:Diet; D005260:Female; D005638:Fruit; D006801:Humans; D008159:Lumbar Vertebrae; D008297:Male; D011188:Potassium / Q000652:urine*; D012964:Sodium / Q000652:urine*; D011795:Surveys and Questionnaires; D014675:Vegetables
D015415:Biomarkers; D012964:Sodium; D011188:Potassium