the Effects of Different Dietary Phosphorus Intake on the Circadian Pattern of Serum Phosphate in Normal Subjects
Condition: Healthy
Study type: Interventional

Summary: 
      The purpose of this study is to investigate the effects of normal diet and low-phosphate diet
      on the level and the circadian pattern of serum phosphate concentration in normal subjects
      and to explore the underlying mechanisms.
    

Detailed description: 
      Emerging evidence show that serum phosphate concentrations are not only associated with
      cardiovascular and all-cause mortality in chronic kidney disease (CKD) patients, but also
      associated with the mortality in community population (without history of CKD or
      cardiovascular disease). The rise of serum phosphate will lead to the elevation of serum
      plasma fibroblast growth factor 23 (FGF23) and parathyroid hormone (PTH) in healthy people,
      contributing to bone disorders and left ventricle thickening. Therefore, maintaining normal
      serum phosphate and reducing postprandial fluctuation of serum phosphate are essential for
      CKD patients as well as healthy people.

      As for serum phosphate modulation by diet, most evidence was focused on CKD patients, less
      focused on healthy people. An American study in 1980s indicated that phosphorus intake was
      significantly related with the level of 24-h serum phosphate and the circadian pattern of
      serum phosphate. However, this study failed to explore the underlying mechanisms and the diet
      in America is different from that in China. Nowadays, normal diet in China is inclined to
      having more calories and protein, which warrants high diet phosphorus intake, may
      contributing to huge fluctuation of serum phosphate and thus elevating the incidence and
      mortality of cardiovascular disease. Therefore, what is the level and circadian pattern of
      serum phosphate concentrations in normal subjects under our native normal diet in China? Is
      restricted phosphate diet able to alter the level and circadian pattern of serum phosphate?
      These questions are what the investigator sare eager to answer.

      Accumulating evidence suggest that gastrointestinal tract has a vital effect in phosphate
      modulation. Berndt etc. suggested that in rat, epidermal cells of duodenum and jejunum could
      sense the gastrointestinal tract phosphate load, rapidly activating the type IIa
      Na/Pi-cotransporter in the renal tubule cells, leading to the increase of urinary phosphate,
      without any changes of serum FGF23, PTH and phosphate concentrations. So the author proposed
      that there had a gastro intestine-kidney axis in phosphate modulation. However, whether this
      axis exists in human body remains unclear.

      Therefore, the investigators plan to conduct a crossover clinical study to evaluate the level
      and circadian pattern of serum phosphate concentrations modulated by native normal diet and
      restricted phosphate diet and then to explore the underlying mechanisms.
    

Intervention name(s): normal diet; restricted phosphate diet
Intervention type(s): Other; Other
Intervention description(s): Diet containing 1500mg of phosphorus; Diet containing 500mg of phosphorus
Allocation: Non-Randomized
Intervention model: Crossover Assignment
Masking: None (Open Label)
Keywords: phosphorus,dietary; circadian rhythm; phosphorus