Data from NHANES 2003-2006 were used to evaluate the relationship between estimated dietary phosphorus intake and the measured serum phosphorus. The following variables were used:
1. Demographics: Age, sex, race/ethnicity
2. Dietary variables: Foods, food groups (as reported by the United States Department of Agriculture (USDA) method, further standardized to the Academy of Nutrition and Dietetics method for portion size and then divided into groups having inorganic phosphate additives or no inorganic phosphate additives), food weight (g), phosphorus (mg), dietary supplements
3. Socioeconomic variables: education, family income
4. Laboratory variables: serum creatinine, phosphorus; urine albumin, creatinine
5. Clinical assessments: hypertension (proportion having blood pressure ≥140 millimeters of mercury (mmHg) diastolic or ≥90 mmHg systolic or taking antihypertensive medications); hyperglycemia (proportion having serum glucose \>126 mg/dL or taking medications for diabetes); kidney function based on Chronic Kidney Disease Epidemiology Collaboration (2009) equation, evaluated in 15 milliliters/min/1.73m2 increments from \<15 to \>105; anthropometrics (BMI, kg/m2; obesity class I, II, III)
