Dietary intake of inorganic phosphorus has a stronger influence on vascular-endothelium function than organic phosphorus

Abstract

Phosphorus management through dietetic therapy is vital for the prevention of cardiovascular disease in chronic kidney disease patients. There are two main sources of phosphorus in the diet, organic phosphorus from protein and inorganic phosphorus from food additives. The adverse effects of high phosphorus intake on vascular-endothelium function have been reported; however, the differences in the effects of organic phosphorus versus inorganic phosphorus are not clear. In this study, we examined an acute effect of these high phosphorus meals intake on vascular-endothelium function. This was a randomized, double-blind, cross-over test study design targeting healthy young men. We conducted a food intake test using two test meals, one high in organic phosphorus from organic food sources, and one high in inorganic phosphorus from food additives. Endothelium-dependent vasodilation, phosphorus and calcium in the urine and blood, and phosphorus-related hormones were measured preprandial to 120 min postprandial. The results showed higher serum and urine phosphorus values after the high inorganic phosphorus meal, and a significant reduction in endothelium-dependent vasodilation at 30 min postprandial. These findings are evidence that inorganic phosphorus has a stronger influence on vascular-endothelium function than organic phosphorus.

Keywords: endothelial function; flow mediated dilation; food additive; inorganic phosphorus.

Fig. 1

Study schema. On the day before the test, all subjects ate a standard meal at 19:00–20:00 and were asked to consume only water after eating. The subjects came to the laboratory in a fasted state and were allowed to drink water after the test meal. We measured %FMD and collected blood and urine samples (▲) at four time points: preprandial (0 min) and 30, 60 and 120 min postprandial. We also took anthropometric measurements and blood pressure at 0 min for the first meal only.

Fig. 2

Changes in serum P (A) and serum Ca (B) over time. The white circles indicate the high organic P meal and the black circles indicate the high inorganic P meal. *p<0.05, **p<0.01 (n = 6).

Fig. 3

Changes in urine P/creatinine (A) and urine Ca/creatinine (B) over time. The white circles indicate the high organic P meal and the black circles indicate the high inorganic P meal. *p<0.05, **p<0.01 (n = 6).

Fig. 4

Changes in the P metabolism regulating hormones serum 1,25(OH)₂D (A), serum intact PTH (B) and serum FGF23 (C) over time. The white circles indicate the high organic P meal and the black circles indicate the high inorganic P meal (n = 6).

Fig. 5

Influence of organic and inorganic P meals on endothelial function over time. Time course of %FMD (A) and relative change of %FMD (B) from preprandial. The white circles indicate the high organic P meal and the black circles indicate the high inorganic P meal. *p<0.05 (n = 6).