Phosphate Intake and Bone and Mineral Biomarkers

Adverse outcomes associated with higher serum phosphate include cardiovascular disease. In patients with chronic kidney disease (CKD), abnormalities of bone and mineral metabolism, including higher serum phosphate, are key risk factors for increased cardiovascular disease. However, according to Marguerite Comley, MNutDiet, BSi (ExSportSci), and colleagues, there are few data available on the associations between dietary phosphate intake and biochemical and cardiovascular parameters in non-dialysis CKD patients.

The researchers conducted a study to examine associations between phosphate intake and biomarkers of bone and mineral metabolism and intermediate cardiovascular markers in adults with CKD stage 3-4. Results were reported in the Journal of Renal Nutrition.

Participants in the Impact of Phosphate Reduction on Vascular End Points in Chronic Kidney Disease trial were asked to join the current sub-study. Dietary phosphate intake and source (animal, plant, or a mixture of both) were determined at baseline using a 7-day self-administered diet food record; measurements of serum and urinary phosphate, serum calcium, parathyroid hormone, fibroblast growth factor-23, and the intermediate cardiovascular markers pulse wave velocity (PWV) and abdominal aortic calcification were obtained. Pearson’s correlation and linear regression were used to explore the relationships between dietary phosphate and those bone metabolism and cardiovascular markers. Compositional data analysis was used to analyze the effect of source of phosphate intake.

The analysis included 90 individuals; 68% were male, mean age was 64 years, estimated glomerular filtration rate was 26.6 mL/min/1.73 m², and dialysis phosphate intake was 1544 mg. Correlations among dietary phosphate and biochemical measures, PWV, and abdominal aortic calcification ranged from  r= –0.13 to r = +0.13. Results of linear regression showed no association between dietary phosphate measurement and biochemical or cardiovascular parameters. There was an association between source of phosphate intake and PWV (P=.01); there was no association with other biomarkers of bone and mineral metabolism. Higher PWV values were associated with higher intake of plant-based relative to animal-based phosphate (1.058, P=.003).

In summary, the authors said, “Levels of total dietary phosphate intake measured by dietary food record show no statistically significant relationship with biochemical markers of bone and mineral metabolism or intermediate cardiovascular markers. Higher PWV level associated with higher intake of plant-based relative to animals-based phosphate intake were an unexpected finding and further research is needed in this area.”