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