Protein Sources Urinary Stone Risk

Prior studies have shown that the source of dietary protein can have a significant impact on urinary stone risk. However, whey and plant protein isolates have not been compared. This is an important distinction as protein supplements fortified foods are increasingly popular. Herein, we seek to investigate the effect of different protein supplements, in an otherwise identical diet, on urinary stone risk.

Each participant will receive a pre-made diet for 5 days at a time, for a total of 4 cycles. Previous studies have shown urine values reach a constant within the first 3 days. Diet will be a constant baseline diet representative of a standard Mediterranean diet. Participants will receive this diet to eat at home for 5 days with a supplemental protein shake at each meal (3 times a day). Participants will be required to drink 2.5-3 liters of fluid daily. Caffeine may be ingested as caffeine pills. Excessive exercise will be discouraged during the treatment phase.

Diet will remain constant with respect to protein quantity and all other ingredients and will only change protein isolate source in supplemental protein shake.

On days 4 and 5 of the diet, participants will be asked to collect two consecutive 24-hour urines. Between each 5-day diet phase, a flexible washout period will be allowed in which participants may eat a self-selected diet to take a break from standardized meals. Participants may resume the next phase diet on a day which is convenient for planned 24-hour urine collection at the end of that phase. The break period is to last no longer than 10 days.

Eligibility Criteria:
Inclusion Criteria:

1. Willing and able to complete the study
2. Healthy with no personal or family history of kidney stones

Exclusion Criteria:

1. Allergy to any protein isolates or menu items used in the study
2. History of calcium oxalate, cysteine, uric acid, or infection stones
3. Disorders of absorption: Celiac disease, Irritable Bowel Disease, chronic diarrhea, short gut
4. Systemic predisposition to stones: gout, congenital hyperuricemia, chronic diarrhea, insulin resistance, neoplastic disorders, hyperparathyroidism or renal tubular acidosis
5. Women who are currently pregnant or planning pregnancy within 2 years
6. Renal transplant recipient
7. Bedridden study participants (ECOG ≥ 3)
8. Uncorrected anatomical obstruction of the urinary tract
9. History of recurrent urinary tract infections (\> 3 urinary tract infections/year proven by urine culture)
10. Exclusions due to medication use:

    1. Chronic use of lithium
    2. Long-term glucocorticoid use (\> 7.5 mg prednisone daily for \> 30 days prior to enrollment)
    3. Intake of narcotic medication on a daily basis for \>30 days prior to enrollment
    4. Supplemental Vitamin C (\> 1 g daily)
    5. Carbonic anhydrase inhibitors (acetazolamide, topiramate, zonisamide)
    6. high dose calcium supplementation (\> 1,200 mg daily)
    7. Medications that may crystallize in the urine (guaifenesin, sulfonamides, triamterene, and the protease inhibitors indinavir and nelfinavir).
11. Non-English Speakers
12. History of Syndrome of Inappropriate Antidiuretic Hormone Secretion (SIADH)
13. Anatomical urologic abnormalities including ileal conduits, horseshoe kidney, megaureter or solitary kidney
14. Psychiatric conditions impairing compliance with the study
15. Vulnerable population (prisoner and/or cognitive impairment that the investigator feels will impact participant's ability to complete study activities)