Potassium quantification and sensory analysis in plant food cooking processes in heart disease patients

Background and objectives

Low potassium (K) diets are recommended for patients at risk of developing hyperkalemia, particularly those with impaired renal function or those who also use medications that can increase serum K levels. In such cases, a K-restricted diet can help reduce the risk of hyperkalemia and, consequently, cardiac arrhythmias and mortality. A diet rich in vegetables, greens, and fruits is essential for the prevention of chronic diseases and plays a vital role in the nutritional therapy of patients with Chronic Kidney Disease (CKD). Factors such as the method of heat transfer, temperature intensity, duration of the process, and the cooking medium used can cause changes in the chemical, physical, and nutritional characteristics of food. Sensory appeal should not be overlooked in favor of therapy alone; recovery efforts must also consider the importance of offering pleasure in the act of eating. This study aimed to quantify the potassium content in vegetables and legumes prepared using different cooking techniques, adapting to patient preferences in order to stimulate intake.

Methods

This was a randomized crossover clinical trial conducted in two phases. The first phase involved potassium content analysis, and the second consisted of a sensory evaluation to assess patient acceptance of the prepared foods at the Institute of Cardiology – University Foundation of Cardiology (IC-FUC), Porto Alegre, Brazil. A total of 68 patients evaluated each food, with a statistical power of 80 % and a significance level of 5 % (95 % confidence interval). Foods were selected based on the TACO table, focusing on those that required cooking and had high potassium content (above 201 mg/100 g). Vegetables and legumes with higher K concentrations were submitted to different cooking techniques.

Results

The vegetables with the lowest potassium values were spinach (74.85 mg/100 g) and zucchini (93.62 mg/100 g), both cooked under pressure. Among the lowest values, only squash (237.83 mg/100 g), also pressure-cooked, exceeded 200 mg/100 g. Among legumes, beans showed potassium levels below this threshold across all methods. For lentils, soaking—regardless of duration—combined with various cooking techniques yielded the best reductions. Pressure cooking resulted in the lowest K losses, followed by boiling in two waters and one water, respectively. These techniques were most effective in preserving potassium. The sautéed method resulted in values above 200 mg/100 g for all vegetables except beetroot (196.23 mg/100 g), while the dry oven method consistently showed values far above recommended levels. ANOVA tests revealed no statistically significant differences in potassium content for legumes across soaking durations or cooking methods. A similar trend was observed for vegetables. Regarding sensory acceptance, no significant differences were found for legumes, as confirmed by the Tukey test. For vegetables, significant differences were found for spinach (p = 0.043) between sautéed (253.23 mg/100 g) and boiling in one water (183.49 mg/100 g; p = 0.055), and for squash (p = 0.037) between pressure cooking (237.83 mg/100 g) and dry oven (460.25 mg/100 g; p = 0.055).

Conclusion

Cooking techniques can alter the concentration of nutrients. Evaluating patient acceptance is crucial for adapting dietary therapy plans. Although many results were not statistically significant, the data are promising and encourage further research. This clinical trial is registered in REBEC (n. 13962).