Abstract
BackgroundNocturnal eating have recently increased. Serum phosphorus levels and regulators of phosphorus have circadian variations, so it is suggested that the timing of eating may be important in controlling serum phosphorus levels. However, there have been no reports on the effects of nocturnal eating on phosphorus metabolism.The objective was to evaluate the effects of nocturnal eating on phosphorus metabolism.MethodsFourteen healthy men participated in two experimental protocols with differing dinner times. The design of this study was a crossover study. The subjects were served test meals three times (breakfast; 07:30 h, lunch; 12:30 h, dinner; 17:30 or 22:30 h) a day. Blood and urine samples were collected to assess diurnal variation until the following morning.ResultsThe following morning, fasting serum phosphorus levels in the late dinner group were markedly higher than those in the early dinner group (p < 0.001), although serum calcium levels were maintained at approximately constant levels throughout the day in both groups. Fluctuations in urinary calcium excretion were synchronized with the timing of dinner eating, however, fluctuations in urinary phosphorus excretion were not synchronized. Urinary phosphorus excretions at night were inhibited in the late dinner group. In the late dinner group, intact parathyroid hormone levels didn’t decrease, and they were significantly higher in this group compared with the early dinner group at 20:00 h (p = 0.004). The following morning, fasting serum fibroblast growth factor 23 levels in the late dinner group had not changed, but those in the early dinner group were significantly increased (p = 0.003). Serum free fatty acid levels before dinner were significantly higher in the late dinner group compared with the early dinner group.ConclusionsOur results indicate that nocturnal eating inhibits phosphorus excretion. It is suggested that nocturnal eating should be abstained from to manage serum phosphorus levels to within an adequate range.
Highlights
FGF 23: fibroblast growth factor 23; Early dinner (Early-D): early dinner; Late dinner (Late-D): late dinner *Significantly different from the Day 1, P = 0.003 phenomenon is thought to be derived to a circadian variation of serum phosphorus
Previous study reported that serum phosphorus levels were lowest in the morning and highest in the middle of the night, and they were greatly modified to the reference levels during a prolonged fast [21]
If the serum phosphorus levels in the morning are higher than the reference value such as Late-D in this study, there is a possibility that the serum phosphorus levels in the afternoon and the middle of the night further rises due to the diurnal variation
Summary
There have been no reports on the effects of nocturnal eating on phosphorus metabolism. The objective was to evaluate the effects of nocturnal eating on phosphorus metabolism. Serum phosphorus levels are maintained within a narrow range (2.5 to 4.5 mg/dL) through a complex interplay between intestinal absorption and renal excretion of phosphorus [1,2,3]. The progressive deterioration of renal function in chronic kidney disease leads to the retention of many substances, including phosphorus and increasing serum phosphorus levels [4]. There is evidence suggesting that high phosphorus intake and hyperphosphatemia may contribute to cardiovascular events among individuals with normal renal function [10,11,12].
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