A new study published in Nutrients compared the effects of increased potassium in the diet from a whole food source – baked / boiled potatoes and baked french fries – or potassium supplement on blood pressure and other risk factors for cardiovascular disease, in comparison to a “typical American”. Control diet (lower potassium intake) in 30 men and women who were pre-hypertensive to hypertensive.
The results showed that including baked / boiled potatoes as part of a typical American diet had the greatest benefit in reducing sodium retention, even more so than the supplement, and resulted in greater reductions in systolic blood pressure compared to the control diet.
In addition, despite widespread misconception about french fries and their role in a heart-healthy lifestyle, the authors observed that a 330-calorie serving of baked french fries, when consumed as part of a typical American diet, had no adverse effects on blood pressure or was Function of blood vessels.
While there is often significant emphasis on reducing dietary sodium intake to better control the risk of blood pressure and cardiovascular disease, this is only half the story. Potassium plays an equally important role, and perhaps the potassium to sodium ratio is most important in the context of the overall dietary matrix, since the potato flour resulted in greater reductions in sodium retention than the potassium supplement alone. “
Connie Weaver, PhD, study director
Evidence for the effect of increased dietary potassium on blood pressure from clinical trials is extremely limited, and this is one of the first known controlled feeding interventions to investigate dietary potassium as the primary variable of interest.
“It is important to establish clinical trials that follow observational studies to establish a causal relationship between diet and health,” notes Weaver. “In this clinical study, for example, baked French fries had no effect on blood pressure, which contradicts observational results, at least in the short term, and helps demonstrate the importance of focusing on a holistic diet approach to maintaining good health compared to someone who overemphasizes avoiding a single food or a group of food. “
Potatoes make up about 20 percent of the vegetable intake in the American diet and help fill several nutrient gaps, including fiber and potassium.1 Eating just one medium-sized potato provides about 10 percent of an adult’s daily potassium requirement.
According to the American Nutrition Guidelines 2020-2025, potassium is an important nutrient that suggests that most Americans are not consuming enough. The mineral has been linked to improvements in cardiovascular and other metabolic health outcomes – including lower blood pressure in patients with high blood pressure. Overall, potatoes and french fries account for approximately 7% and 3%, respectively, of potassium intake in the United States
“When you consider that Americans are significantly short of daily potassium intake, these results show the importance of promoting, rather than restricting, whole, good-to-excellent sources of potassium such as potatoes in American diets,” said Weaver.
A closer look at the study methodology, strengths and limits
Participants were randomly assigned to one of four 16-day dietary potassium interventions:
- Control diet with 2300 mg potassium / day (corresponds to the typical intake, is considered “low in potassium”)
- Control diet + 1000 mg potassium from potatoes (baked, boiled or heated in a pan without additional fat)
- Control diet + 1000 mg from baked French fries
- Control diet + 1000 mg from a potassium gluconate supplement
Each diet was tailored to the specific calorie needs of the participants while all other nutrients were kept constant. Blood pressure was measured at multiple visits to each phase, and participants also collected daily urine / stool samples to assess potassium and sodium excretion and retention.
The study’s strengths include tightly controlled diet, cross-over design, and excellent compliance. However, the researchers also note some limitations, including the relatively small sample size of the study, poor retention in study participation, and the relatively short study duration.
“All clinical trials are faced with limitations; however, despite what was found in this study, the study design is rigorous and unlike any other study that examined the effects of whole foods – and potassium – on high blood pressure, ”Weber notes.
“Through our carefully controlled balance study, we were able to determine the mechanism by which potatoes lower blood pressure. Overall, we concluded that boiled or baked potatoes can lower systolic blood pressure – and baked french fries have no negative effects on blood pressure and can be part of an overall healthy diet. “
Alliance for Potato Research and Education
Stone, MS, et al. (2021) Short-term RCT of increased dietary potassium from potatoes or potassium gluconate: Effects on blood pressure, microcirculation, and potassium and sodium retention in pre-hypertensive to hypertensive adults. Nutrient. doi.org/10.3390/nu13051610.