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NCT Number: NCT02020785

Study of Dietary Additive Phosphorus on Proteinuria and Fibroblast Growth Factor-23

Phosphorus-based food additives are commonly used by food manufacturers for many applications, such as enhancing flavor, in ready-to-eat foods and beverages. While these additives can significantly increase an individual's daily phosphorus intake, little is known about the effect of dietary phosphorus on kidney health. In this study, the investigators will first lower baseline phosphorus intake to about 1000mg/d by educating participants to avoid foods with phosphorus additives. Then, participants will be randomized to a higher phosphorus period (~2gm/d) and a lower phosphorus period (~1gm/d) by providing unaltered, commercially-available food/beverage products with and without phosphorus additives.

The investigators hypothesize that participants will have higher urine albumin excretion and fibroblast growth factor-23 (FGF-23) during the higher phosphorus period compared to the lower phosphorus period.

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Key information

Conditions

Albuminuria Female Urogenital Diseases Female Urogenital Diseases and Pregnancy Complications Male Urogenital Diseases Pathological Conditions, Signs and Symptoms Proteinuria Signs and Symptoms Urination Disorders Urogenital Diseases Urologic Diseases Urological Manifestations

Age range

21 year and older

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

Primary location

Prohealth Clinical Research Unit

Baltimore, Maryland, 21207, United States

About this study

The Study of Dietary Additive Phosphorus on Proteinuria and FGF-23 (SODA-POP) was a single-center, randomized, double-blind, two-period cross-over study that examined the effect of higher vs. lower phosphorus intake for 3 week periods, achieved by addition of commercially available diet beverages and breakfast bars to diet on albuminuria and fibroblast growth factor 23, in adults with presumed early chronic kidney disease (estimated glomerular filtration rate >= 45 ml/min/1.73m2; and urine albumin/creatinine ratio >=17 mg/g for men or >=25 mg/g for women).

Who can participate

Healthy volunteers accepted: No

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

Adults at least 21 years of age with at least microalbuminuria

Exclusion criteria

Estimated glomerular filtration rate <45ml/min/1.73m2, poorly controlled diabetes or hypertension, nephrotic syndrome, hyperparathyroidism, Paget's Disease, multiple myeloma, uncontrolled thyroid disease, chronic antacid use, use of phosphorus binders, phosphorus supplements, or high-dose vitamin D, inability to complete feeding study, investigator discretion

Treatment and study plan

Higher phosphorus period

Other

Commercially-available unaltered food/beverage products containing phosphorus additives (~1gm/d of phosphorus) will be given for 3 weeks.

All participants at the beginning of the study will receive dietary education to reduce their baseline consumption of phosphorus to a goal of ~1gm/d by receiving education on avoiding phosphorus-based additives.

Lower phosphorus period

Other

Commercially-available unaltered food/beverage products without phosphorus additives (<10mg/d of phosphorus) will be given for 3 weeks.

All participants at the beginning of the study will receive dietary education to reduce their baseline consumption of phosphorus to a goal of ~1gm/d by receiving education on avoiding phosphorus-based additives.

Primary outcomes

  1. 24-hour Urine Albumin Excretion

    Time frame: 3 weeks

    Two 24-hour urine collections will be collected during the 3rd week of each period

  2. Fibroblast Growth Factor-23 (FGF-23)

    Time frame: 3 weeks

    Plasma FGF-23 will be measured at the end of each 3 week period in the morning after an overnight fast.

    As this is a small pilot study, we will not adjust for multiple comparisons. A p value<0.05 will be considered statistically significant for both outcomes

Secondary outcomes

  1. Systolic Blood Pressure

    Time frame: 2-3 weeks

    Blood pressure was measured at the end of weeks 1, 2, and 3. At each visit, 3 readings were obtained in the seated position by trained and certified observers after 5 minutes of rest with an Omron HEM-907 device (Omron Healthcare Inc, Bannockburn, Ill) using a standardized protocol. We used the average of all blood pressure measurements at the end of weeks 1, 2, and 3 for each period.

  2. Diastolic Blood Pressure

    Time frame: 2-3 weeks

    Blood pressure measured at the end of weeks 1, 2, and 3. At each visit, 3 readings were obtained in the seated position by trained and certified observers after 5 minutes of rest with an Omron HEM-907 device (Omron Healthcare Inc, Bannockburn, Ill) using a standardized protocol. We used the average of all these readings taken during end of weeks 1, 2, and 3 for each period.

Sponsors and collaborators

Lead sponsor

Geisinger Clinic

Other

Collaborators

  • Johns Hopkins University

Registry information

Official study title

Randomized Cross-over Study Examining the Effects of Phosphorus Additives on Urinary Albumin Excretion and Fibroblast Growth Factor-23

Acronym: SODA-POP

Important dates

Study start
2014
Primary completion
2015
Study completion
2015
First posted
Dec 25, 2013
Registry last updated
Jun 5, 2019

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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