Potassium supplements in the amount of at least 2,400 mg per day lower blood pressure, according to an analysis of 33 trials.¹ However, potassium supplements greater than 100 mg per tablet require a prescription, and the low-dose potassium supplements available without a prescription can irritate the stomach if taken in large amounts. Moreover, some people, such as those taking potassium-sparing diuretics, should not take potassium supplements. Therefore, the use of potassium supplements for lowering blood pressure should only be done under the care of a doctor.

Patients taking hydrochlorothiazide for high blood pressure had a significant reduction in arrhythmias when supplemented with 1 gram twice per day of potassium hydrochloride (supplying 1040 mg per day of elemental potassium). Those results were not improved by adding 500 mg twice per day of magnesium hydroxide (supplying 500 mg per day of elemental magnesium) to the potassium.² Low serum concentrations of potassium were found to be associated with a higher incidence of arrhythmia in a large population study.³

The combination of potassium aspartate and magnesium aspartate has shown benefits for chronically fatigued people in double-blind trials.^{4, 5, 6, 7} However, these trials were performed before the criteria for diagnosing CFS was established, so whether these people were suffering from CFS is unclear. Usually 1 gram of aspartates is taken twice per day, and results have been reported within one to two weeks.

Magnesium deficiency frequently occurs in people with CHF, and such a deficiency may lead to heart arrhythmias. Magnesium supplements have reduced the risk of these arrhythmias.⁸ People with CHF are often given drugs that deplete both magnesium and potassium; a deficiency of either of these minerals may lead to an arrhythmia.⁹ Many doctors suggest magnesium supplements of 300 mg per day.

Whole fruit and fruit and vegetable juice, which are high in potassium, are also recommended by some doctors. One study showed that elderly men who consumed food prepared with potassium-enriched salt (containing about half potassium chloride and half sodium chloride) had a 70% reduction in deaths due to heart failure and a significant reduction in medical costs for cardiovascular disease, when compared with men who continued to use regular salt.¹⁰ While increasing potassium intake can be beneficial for heart patients, this dietary change should be discussed with a healthcare provider, because several drugs given to people with CHF may actually cause retention of potassium, making dietary potassium, even from fruit, dangerous.