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Retention of Potassium From Potatoes and Potassium Gluconate, and the Effect on Blood Pressure.

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ClinicalTrials.gov Identifier: NCT02697708
Recruitment Status : Unknown
Verified May 2018 by Berdine Martin, Purdue University.
Recruitment status was:  Active, not recruiting
First Posted : March 3, 2016
Last Update Posted : May 9, 2018
Alliance for Potato Research and Education
Information provided by (Responsible Party):
Berdine Martin, Purdue University

Brief Summary:
This study is designed to compare the effect of different dietary potassium sources on uptake and retention of potassium, as well as to determine the effect of potassium intake on blood pressure and acid-base balance. The study will compare three different sources of potassium given as a supplement, potatoes or French fries.

Condition or disease Intervention/treatment Phase
Hypertensive Disease Dietary Supplement: Potassium control diet Dietary Supplement: Potassium gluconate diet Dietary Supplement: Potato Diet Dietary Supplement: French Fries Diet Phase 1 Phase 2

Detailed Description:

Potassium is a shortfall nutrient according to the 2010 Dietary Guidelines for Americans. Only 3% of Americans meet the recommended Adequate Intake of 4700 mg/d for potassium. Average potassium intake is approximately half of the Recommended Dietary Allowance (RDA), with potatoes providing the highest percentage (19-20% of potassium) in the American diet. Recommended dietary potassium intakes were determined primarily to optimize protection against hypertension and secondarily to protect against stroke and coronary heart disease. In setting requirements for most minerals, bioavailability is usually considered. However, little is known about bioavailability of potassium and what is known is from supplements rather than food. Recently, we performed a potassium bioavailability study on white potatoes looking at 35 healthy, normotensive men and women at 3 levels of potassium intake as potatoes or potassium gluconate supplements. Bioavailability of potassium was determined from AUC of serial blood draws and cumulative urinary excretion. Serum potassium Area Under the Curve (AUC )increased with dose (P<0.0001) and did not differ due to source (p=0.52). Cumulative 24 h urinary potassium also increased with dose (p<0.0001) and was greater with potato than supplement (p<0.0001), concluding that bioavailability of potassium is as high from potatoes as from supplements. These data allow us to evaluate the quality of the food as a source of potassium. However, a remaining question is whether retention of potassium from potatoes is higher than from the salt, which requires a metabolic balance study to determine. The effects of potassium rich foods on blood pressure have also been recently accessed. A controlled feeding study would properly capture potassium retention and balance, as well as adequately control for any positive benefit potassium may have on blood pressure and other vascular outcomes.

Increasing potassium citrate decreased titratable acidity and improved calcium retention in a dose response manner in postmenopausal women. There is one Randomized Controlled Trial (RCT) of potassium on bone, in postmenopausal women, showing a benefit of a supplement of potassium chloride on protecting against bone loss. Similar studies have not been performed with food sources of potassium.

This study is designed to evaluate the effect of added potassium (K) from potatoes in the diet on K retention , blood pressure, and parameters related to bone health including calcium retention and acid base balance.

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Study Type : Interventional  (Clinical Trial)
Actual Enrollment : 40 participants
Allocation: Randomized
Intervention Model: Crossover Assignment
Intervention Model Description: Participants will receive a controlled diet containing 2340 mg potassium.(K) During the 4 - 16 day phases they will receive an additional 0 mg K, 1000 mg K from potatoes, 1000 mg K from French Fries, and 1000 mg K from supplement in randomized order. Blood pressure will be measured every other day during the intervention. There will be a 2 week washout phase during each phase.
Masking: None (Open Label)
Primary Purpose: Prevention
Official Title: The Effect of Potatoes on Potassium Retention, Acid Base Balance, and Blood Pressure
Actual Study Start Date : April 27, 2016
Estimated Primary Completion Date : August 2018
Estimated Study Completion Date : December 31, 2018

Resource links provided by the National Library of Medicine

MedlinePlus related topics: Potassium

Arm Intervention/treatment
Placebo Comparator: Control Diet
Control (no additional potassium added to diet): Arm will consist of a 16 day balance period with a basal diet set at ~2340mg K/day; based on average American intake.
Dietary Supplement: Potassium control diet
No additional potassium.
Other Name: Control Diet

Active Comparator: Potassium Supplement Diet
Potassium gluconate: Arm will consist of a 16 day balance period with the basal (control) diet plus the addition of 1000mg of K/day from potassium gluconate (12 tablets).
Dietary Supplement: Potassium gluconate diet
1000 mg K from potassium gluconate.

Experimental: Potato Diet
Potato diet: Arm will consist of a 16 day balance period with a basal (control) diet with an addition of 1000mg of K/day from white potatoes.
Dietary Supplement: Potato Diet
1000 mg K from potatoes.

Experimental: French fries Diet
French fry diet: Arm will consist of a 16 day balance period with a basal (control) diet with an addition of 1000mg K/day from French fries.
Dietary Supplement: French Fries Diet
1000 mg K from French Fries.

Primary Outcome Measures :
  1. Change in systolic blood pressure [ Time Frame: 1, 3, 6, 8, 10, 12, 14, 16 days ]
    Systolic blood pressure measured directly three consecutive times after 15 min of supine rest.

  2. Potassium balance/retention [ Time Frame: Through out each day of each 16 day intervention ]
    Twenty four hour urine and feces will be collected on all intervention days of each phase. Urine will be analyzed for creatinine, K, Na, Ca, Mg according to the urine protocol. Some urine will be stored for future analysis and the rest discarded.

  3. Potassium serum kinetics [ Time Frame: Day 16 (24 hours) of each intervention period ]
    Following breakfast, which will include the respective source of potassium or control, pooled urine will be collected at 2, 4, 6, 12 and 24.h. Blood will be drawn (5ml each draw) at 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 6 and 24 hours post breakfast meal. , A catheter will be inserted in the arm at baseline and will be kept there until the blood draw at 6 hours. A needle will be used for the sample at 24 hours. BP will be measured after 4, 6, and 24h.

Secondary Outcome Measures :
  1. Change in microcirculation [ Time Frame: 1, and 16 days ]
    Vascular flow rate measured via Laser Doppler Flowmetry from right forearm for 60 min from the supine position.

  2. Change in vascular flow rate [ Time Frame: 1, 16 days ]
    Central blood pressure will be measured by pulse wave analysis. Measurements will be repeated at least three times within a 20 minute period after the subject has rested for at least 10 minutes in a seated position. The staff member will place a tonometer (pressure sensor) on the wrist to detect the radial pulse waveform. Measurements will be taken over the course of 5-15 minutes or until pulse wave signal reaches data acquisition parameters.

  3. Acid-base balance [ Time Frame: 14, 15 days ]
    Acid-base balance will be determined on two-end of phase 24 h urine collection to relate to urinary calcium and potassium excretion. Pre-prandial arterialized blood samples will be collected anaerobically using forearm venous blood from the heated hand (10) into a polypropylene syringe containing lyophilized lithium heparin. The blood samples will be stored at room temperature and analyzed within 1 h of collection. Renal acid-base balance will be measured using urinary Net Acid Excretion (NAE) and Potential Renal Acid Load (PRAL).

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Ages Eligible for Study:   21 Years and older   (Adult, Older Adult)
Sexes Eligible for Study:   All
Accepts Healthy Volunteers:   Yes

Inclusion Criteria:

  • Age 21 and above
  • Subjects able to adhere to the visit schedule and protocol requirements and be available to complete the study.
  • Pre-hypertensive, (SBP: 120-159mmHg).

Exclusion Criteria:

  • Subjects taking more than one medication to treat hypertension
  • Subject is taking medication to treat hypotension, or medication known to affect electrolyte metabolism or contain high levels of potassium or sodium, smoke cigarettes, use illegal drugs, or excessive alcohol intake.
  • Current use systemic corticosteroids, androgens, phenytoin, erythromycin, thyroid hormones, lipid-lowering medication.
  • Subjects who have hypertension (SBP > 160 mmHg), hypotension (SBP < 120mmHg) or diseases known to affect potassium metabolism (kidney disease or malabsorption disorders). History of myocardial infarction, diabetes mellitus, renal disease, gastrointestinal disease, pancreatitis, cholestatic liver disease, cancer.
  • Subjects who are pregnant.
  • Allergy or intolerance of intervention foods.
  • Unwillingness to refrain from dietary supplements.
  • Weight loss > 3kg in the past 2 months.
  • Subjects with liver and/or lipid abnormalities (elevated alanine amino transferase (ALT) and aspartate amino transferase (AST), dyslipidemia).

Information from the National Library of Medicine

To learn more about this study, you or your doctor may contact the study research staff using the contact information provided by the sponsor.

Please refer to this study by its ClinicalTrials.gov identifier (NCT number): NCT02697708

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United States, Indiana
Department of Nutrition Science Purdue University
West Lafayette, Indiana, United States, 47907-2059
Sponsors and Collaborators
Purdue University
Alliance for Potato Research and Education
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Principal Investigator: Connie Weaver, PhD Purdue University, Nutrition Science
Publications automatically indexed to this study by ClinicalTrials.gov Identifier (NCT Number):
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Responsible Party: Berdine Martin, Research Scientist, Purdue University
ClinicalTrials.gov Identifier: NCT02697708    
Other Study ID Numbers: 1511016780
First Posted: March 3, 2016    Key Record Dates
Last Update Posted: May 9, 2018
Last Verified: May 2018
Individual Participant Data (IPD) Sharing Statement:
Plan to Share IPD: Undecided
Additional relevant MeSH terms:
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Vascular Diseases
Cardiovascular Diseases