The purpose of the study is to learn more about how phosphorus-based food additives affect phosphorus metabolism in people with normal kidney function.

Phosphorus is a mineral that is found in foods such as dairy products, nuts, and meat, and is important for strengthening the bones. However, too much phosphorus in the blood may be bad for the health of your heart and blood vessels. The kidneys keep the blood levels of phosphorus normal by getting rid of extra phosphorus in the urine. New research has found that common forms of food additives that are high in phosphorus may increase blood phosphorus levels in individuals with kidney disease. In addition, these food additives may increase blood levels of hormones that control phosphorus such as parathyroid hormone (PTH) and fibroblast growth factor 23 (FGF23). Like high blood phosphorus levels, high levels of PTH and FGF23 in the blood may also be bad for the health of your heart and blood vessels. In this study, the investigators would like to examine the effects of food additives on blood levels of phosphorus, PTH and FGF23 in individuals with normal kidney function.

Inclusion Criteria:

• Healthy volunteers, 19 - 45 years of age

Exclusion Criteria:

• abnormal urinalysis-presence of hematuria, proteinuria, or leukocyturia.
• pregnancy or breast-feeding
• Medical conditions impacting phosphate metabolism-primary hyperparathyroidism; gastrointestinal malabsorption disorders such as Crohn's Disease, ulcerative colitis, celiac disease, or liver dysfunction; hyper- or hypothyroidism; irregular menses for female subjects.
• Body Mass Index (BMI) ≥ 30 g/m2 since obesity is independently associated with impaired phosphorus metabolism.
• Medications known to affect phosphorus metabolism- current use of phosphorus supplements, high-dose or activated vitamin D compounds, regular antacid or laxative use, anticonvulsants.
• Hyper- or hypophosphatemia (≥ 4.6 mg/dl or ≤ 2.5 mg/dl respectively), hyper- or hypocalcemia (≥ 10.6 or ≤ 8.5 mg/dl respectively), or severe anemia (hemoglobin < 8 g/dl for women and < 9 g/dl for men).