The Impact of a Low or High Phosphate Diet on Phosphate and Calcium Excretion in Healthy People

Study Overview
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Brief Summary
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Phosphate is present in many of the foods that the investigators eat and is required by many cellular processes. The kidneys are the only organ that excrete the extra phosphate from the diet that the body does not require. Phosphate is linked to vascular calcification and cardiovascular disease. Measures of serum phosphate do not reflect the burden of phosphate and are not sensitive to early changes in the way the kidneys eliminate phosphate. This study will determine whether the kidneys handle an oral phosphate load differently after 5 days of a low phosphate diet compared to 5 days of a high phosphate diet.

Detailed Description
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In this study, participants will follow a low-phosphorus diet (750 mg) with a 500 mg calcium supplement for 5 days keeping a detailed diary of the foods eaten during this period. On the 5th day, the participant will undergo a 24 hour urine collection. Participants will present after an overnight fast for baseline blood and urine measurements. Then they will consume water containing 500 mg of phosphorus. Urine and blood will be collected every hour for 3 hours for measurement of phosphate and calcium and for measurement of hormones known to regulate phosphate and calcium including fibroblast growth factor-23, parathyroid hormone and vitamin D. One week later, participants will follow the same diet but will also receive a 1250 mg phosphorus supplement for 5 days. On the 5th day, urine will be collected for 24 hours. Participants will present again after an overnight fast and undergo the identical testing.

Official Title
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The Impact of a Low or High Phosphate Diet on Phosphate and Calcium Excretion in Healthy People

Conditions
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Cardiovascular Diseases, Aging, Nutrient; Excess

Intervention / Treatment
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* Dietary Supplement: Phosphate supplemented diet


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: healthy between ages of 20 and 40 Exclusion Criteria: known heart disease known diabetes pregnant breast-feeding

Ages Eligible for Study
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Minimum Age: 20 Years
Maximum Age: 40 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Other
Allocation: Randomized
Intervention Model: Crossover Assignment
Interventional Model Description: Randomized, cross-over design
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Active Comparator: Phosphate supplemented diet<br>All participants will undergo phosphate testing after following a phosphate supplemented diet for 5 days | Dietary Supplement: Phosphate supplemented diet<br>* Participants will be asked to follow a 5 day menu of 750 mg of phosphorus daily along with a daily sodium phosphorus supplement of 500 mg<br>* Other names: sodium phosphate;|
| No Intervention: Low phosphate diet<br>All participants will undergo phosphate testing after following a low phosphate diet for 5 days | |

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Urinary phosphate excretion | Change in urinary phosphate excretion after 500 mg phosphorus challenge | 3 hours |