Regression equation for predicting dietary phosphorus intake based on estimated dietary protein intake: A multicenter...

Protein and phosphorus intake, which affect chronic kidney disease (CKD), is assessed using cumbersome food diaries. Therefore, more straightforward and accurate methods of assessing protein and phosphorus intake are needed. We decided to investigate the nutrition status and dietary protein and phosphorus intake of patients with stages 3, 4, 5, or 5D CKD.

This cross-sectional survey included outpatients with CKD at seven class A tertiary hospitals in Beijing, Shanghai, Sichuan, Shandong, Liaoning, and Guangdong in China. Protein and phosphorus intake levels were calculated using 3-day food records. Protein levels and calcium and phosphorus serum concentrations were measured; urinary urea nitrogen was determined using a 24-h urine test. Protein and phosphorus intakes were calculated using the Maroni and Boaz formulas, respectively. The calculated values were compared with the recorded dietary intakes. An equation that regressed phosphorus intake on protein intake was constructed.

The average recorded energy and protein intake was 1637.5 ± 595.74 kcal/day and 56.97 ± 25.25 g/day, respectively. Overall, 68.8% of patients had a good nutrition status (grade A on the Subjective Global Assessment). The correlation coefficient between protein intake and calculated intake was 0.145 (P = 0.376) and that between phosphorus intake and calculated intake was 0.713 (P < 0.001).

Protein and phosphorus intakes correlated linearly. Chinese patients with stage 3-5 CKD had low daily energy intake but high protein intake. Malnutrition was present in 31.2% of patients with CKD. The phosphorus intake could be estimated from the protein intake.