A study published in Nutrients researched the effect of increased dietary potassium from a whole food supply–baked/boiled potato and baked French fries–or a potassium supplement on blood pressure and other cardiovascular disease risk factors compared to some ‘typical American’ control diet (lower potassium consumption ) among 30 pre-hypertensive to hypertensive women and men. Results showed that adding baked/boiled potato consumption as part of a typical American diet had the greatest benefit on reducing sodium retention, more than the nutritional supplement, and resulted in a higher systolic blood pressure decrease compared to the control diet. Further, despite commonly held misbeliefs about French fries and their function in heart-healthy life, the authors observed a 330-calorie serving of baked French fries, when eaten as part of a typical American diet, had no adverse impact on blood pressure or blood vessel function.
“While significant emphasis is often placed on reducing dietary sodium intakes to better control for blood pressure and cardiovascular disease risk, that’s only half of the story,” says Connie Weaver, PhD, the primary investigator. “Potassium plays just as an important role, and perhaps the ratio of potassium to sodium is most important in the context of the entire food matrix, as the potato meal resulted in a greater reduction of sodium retention than the potassium supplement alone.”
Evidence on the effect of increased dietary potassium on blood pressure from clinical trials is very limited, and this is among the first recognized controlled feeding interventions exploring dietary potassium as the primary factor of interest.
“It’s important to establish clinical trials that follow observational research to establish a causal link between diet and health,” notes Weaver. “For example, in this clinical study baked French fries had a null effect on blood pressure, which counters observational findings, at least in the short term, and helps to prioritize the importance of focusing on a total diet approach for maintaining health versus one that overemphasizes avoidance of any single food or food group.”
Potatoes comprise roughly 20% of the vegetable intake in the American diet and help fill several nutrient openings, such as dietary fiber and potassium. Eating just 1 medium potato meets roughly 10 percent of an adult’s daily potassium needs. In accordance with this 2020-2025 Dietary Guidelines for Americans, potassium is an essential nutrient of concern, suggesting most Americans aren’t consuming enough. The vitamin has been linked to improvements in cardiovascular and other metabolic health effects – such as decreased blood pressure in those with hypertension. Overall, potatoes and French fries represent approximately 7 percent and 3 percent of potassium consumption, respectively, in the United States.
“Considering Americans fall significantly short in meeting daily potassium intakes, these findings show the importance of promoting, not restricting, whole food good-to-excellent sources of potassium in Americans’ diets, like potatoes,” Weaver said.
A Closer Look at the Study Methodology, Strengths and Limitations
Participants were randomly assigned to one of four 16-day dietary potassium interventions:
Control diet including 2300 mg potassium/day (reflective of typical intake, considered to be ‘low potassium’)
Control diet + 1000 mg of potassium in potatoes (baked, boiled, or pan-heated with no extra fat)
Control diet + 1000 mg from baked fries
Control diet + 1000 mg by a potassium-gluconate supplement
Each diet was tailored to participants’ specific caloric demands while the rest of the nutrients were kept constant. Blood pressure was measured across several visits of each stage, and participants gathered daily urine/stool samples to estimate sodium and potassium excretion and retention.
The strengths of this study include a highly regulated diet, cross-over design, and excellent compliance. On the other hand, the researchers note a few limitations also, including the study’s relatively modest sample size, inadequate retention in research participation and comparatively short study duration.
“All clinical studies are faced with limitations; however, despite those found in this study, the rigor of the study design is strong and unlike any other studies that have investigated the effect of a whole food – and potassium – on high blood pressure,” Weaver notes. “Through our carefully controlled balance study, we could determine the mechanism by which potatoes reduced blood pressure. Overall, we concluded that boiled or baked potatoes can help reduce systolic blood pressure – and baked French fries have no adverse effects on blood pressure and can be included as part of an overall healthy diet.”
The research manuscript, “Short-term randomized controlled trial of increased dietary potassium from potato or potassium gluconate: effect on blood pressure, microcirculation, and potassium and sodium retention in pre-hypertensive-to-hypertensive adults,” is published in Nutrients (doi: https://doi.org/10.3390/nu13051610). Authors include Michael Stone, Berdine Martin and Connie Weaver of Purdue University. Funding was provided from the Alliance for Potato Research and Education.