Low calcium:phosphorus ratio in habitual diets affects serum parathyroid hormone concentration and calcium metabolism in healthy women with adequate calcium intake

Br J Nutr. 2010 Feb;103(4):561-8. doi: 10.1017/S0007114509992121. Epub 2009 Sep 28.


Excessive dietary P intake alone can be deleterious to bone through increased parathyroid hormone (PTH) secretion, but adverse effects on bone increase when dietary Ca intake is low. In many countries, P intake is abundant, whereas Ca intake fails to meet recommendations; an optimal dietary Ca:P ratio is therefore difficult to achieve. Our objective was to investigate how habitual dietary Ca:P ratio affects serum PTH (S-PTH) concentration and other Ca metabolism markers in a population with generally adequate Ca intake. In this cross-sectional analysis of 147 healthy women aged 31-43 years, fasting blood samples and three separate 24-h urinary samples were collected. Participants kept a 4-d food record and were divided into quartiles according to their dietary Ca:P ratios. The 1st quartile with Ca:P molar ratio < or = 0.50 differed significantly from the 2nd (Ca:P molar ratio 0.51-0.57), 3rd (Ca:P molar ratio 0.58-0.64) and 4th (Ca:P molar ratio > or = 0.65) quartiles by interfering with Ca metabolism. In the 1st quartile, mean S-PTH concentration (P = 0.021) and mean urinary Ca (U-Ca) excretion were higher (P = 0.051) than in all other quartiles. These findings suggest that in habitual diets low Ca:P ratios may interfere with homoeostasis of Ca metabolism and increase bone resorption, as indicated by higher S-PTH and U-Ca levels. Because low habitual dietary Ca:P ratios are common in Western diets, more attention should be focused on decreasing excessively high dietary P intake and increasing Ca intake to the recommended level.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Bone Density Conservation Agents / administration & dosage
  • Bone Density Conservation Agents / metabolism*
  • Bone Density Conservation Agents / urine
  • Bone Resorption / blood
  • Bone Resorption / metabolism
  • Calcium / administration & dosage
  • Calcium / metabolism*
  • Calcium / urine
  • Calcium, Dietary / administration & dosage
  • Calcium, Dietary / metabolism*
  • Cross-Sectional Studies
  • Diet / adverse effects*
  • Diet Records
  • Female
  • Homeostasis
  • Humans
  • Micronutrients
  • Minerals
  • Nutritional Status
  • Osteoporosis / prevention & control
  • Parathyroid Hormone / blood*
  • Phosphorus, Dietary / administration & dosage
  • Phosphorus, Dietary / adverse effects*
  • Phosphorus, Dietary / metabolism
  • Reference Values


  • Bone Density Conservation Agents
  • Calcium, Dietary
  • Micronutrients
  • Minerals
  • Parathyroid Hormone
  • Phosphorus, Dietary
  • Calcium