Bioavailability of potassium from potatoes and potassium gluconate: A randomized dose response trial

Abstract

Background: The bioavailability of potassium should be considered in setting requirements, but to our knowledge, the bioavailability from individual foods has not been determined. Potatoes provide 19-20% of potassium in the American diet. Objective: We compared the bioavailability and dose response of potassium from nonfried white potatoes with skin [targeted at 20, 40, and 60 milliequivalents (mEq) K] and French fries (40 mEq K) with potassium gluconate at the same doses when added to a basal diet that contained ∼60 mEq K. Design: Thirty-five healthy, normotensive men and women with a mean 6 SD age of 29.7 6 11.2 y and body mass index (in kg/m2) of 24.3 6 4.4 were enrolled in a single-blind, crossover, randomized controlled trial. Participants were partially randomly assigned to the order of testing for nine 5-d interventions of additional potassium as follows: 0 (control; repeated at phases 1 and 5), 20, 40, and 60 mEq K/d consumed as a potassium gluconate supplement or as unfried potato or 40 mEq K from French fries completed at phase 9. The bioavailability of potassium was determined from the area under the curve (AUC) of serial blood draws and cumulative urinary excretion during a 24-h period and from a kinetic analysis. The effects of the potassium source and dose on the change in blood pressure and augmentation index (AIx) were determined. Results: The serum potassium AUC increased with the dose (P, 0.0001) and did not differ because of the source (P = 0.53). Cumulative 24-h urinary potassium also increased with the dose (P, 0.0001) and was greater with the potato than with the supplement (P, 0.0001). The kinetic analysis showed the absorption efficiency was high across all interventions (.94% 6 12%). There were no significant differences in the change in blood pressure or AIx with the treatment source or dose. Conclusions: The bioavailability of potassium is as high from potatoes as from potassium gluconate supplements. Future studies that measure the effect of dietary potassium on blood pressure will need to evaluate the effect of various dietary sources on potassium retention and in both normal and hypertensive populations.