title: High phosphorus intakes acutely and negatively affect Ca and bone metabolism in a dose-dependent manner in healthy young females.
abstract: Ca and P are both essential nutrients for bone and are known to affect one of the most important regulators of bone metabolism, parathyroid hormone (PTH). Too ample a P intake, typical of Western diets, could be deleterious to bone through the increased PTH secretion. Few controlled dose-response studies are available on the effects of high P intake in man. We studied the short-term effects of four P doses on Ca and bone metabolism in fourteen healthy women, 20-28 years of age, who were randomized to four controlled study days; thus each study subject served as her own control. P supplement doses of 0 (placebo), 250, 750 or 1500 mg were taken, divided into three doses during the study day. The meals served were exactly the same during each study day and provided 495 mg P and 250 mg Ca. The P doses affected the serum PTH (S-PTH) in a dose-dependent manner (P=0.0005). There was a decrease in serum ionized Ca concentration only in the highest P dose (P=0.004). The marker of bone formation, bone-specific alkaline phosphatase, decreased (P=0.05) and the bone resorption marker, N-terminal telopeptide of collagen type I, increased in response to the P doses (P=0.05). This controlled dose-response study showed that P has a dose-dependent effect on S-PTH and increases PTH secretion significantly when Ca intake is low. Acutely high P intake adversely affects bone metabolism by decreasing bone formation and increasing bone resorption, as indicated by the bone metabolism markers.
authors.affiliation: Calcium Research Unit, Department of Applied Chemistry and Microbiology, P.O. Box 66, University of Helsinki, FIN-00014 Helsinki, Finland.
authors.forename: Virpi E
authors.initials: VE
authors.lastname: Kemi
authors.forename: Merja U M
authors.initials: MU
authors.lastname: Kärkkäinen
authors.forename: Christel J E
authors.initials: CJ
authors.lastname: Lamberg-Allardt
mesh_terms: D000328:Adult; D000469:Alkaline Phosphatase / Q000097:blood; D015415:Biomarkers / Q000097:blood; D001862:Bone Resorption / Q000097:blood; D001842:Bone and Bones / Q000378:metabolism*; D002118:Calcium / Q000097:blood / Q000378:metabolism*; D024042:Collagen Type I / Q000097:blood; D004032:Diet; D019587:Dietary Supplements; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D010012:Osteogenesis / Q000502:physiology; D010281:Parathyroid Hormone / Q000097:blood; D010455:Peptides / Q000097:blood; D010710:Phosphates / Q000097:blood / Q000652:urine; D010758:Phosphorus / Q000008:administration & dosage*; D014807:Vitamin D / Q000031:analogs & derivatives / Q000097:blood
chemical_list: D015415:Biomarkers; D024042:Collagen Type I; D010281:Parathyroid Hormone; D010455:Peptides; D010710:Phosphates; C052929:collagen type I trimeric cross-linked peptide; D014807:Vitamin D; D010758:Phosphorus; C097949:1,25-dihydroxyvitamin D; D000469:Alkaline Phosphatase; D002118:Calcium