Potassium is a major intracellular cation — a positively charged ion. The average human body contains 245 grams of potassium, about 95 percent of which is found inside cells.

Potassium is found in a variety of foods, including:

• Avocados

• Bananas

• Cantaloupe

• Leafy green vegetables

• Mango

• Melon

• Papaya

• Prunes

• Winter squash

• Yams

Nuts, legumes, seeds, and peanut butter are also good sources, and dairy products may contain some potassium. More than 85 percent of the potassium in food is absorbed.

Potassium is necessary for the contraction of smooth muscles as well as skeletal and cardiac muscle. It helps increase the excitability of nerve tissue, and is also important for regulating electrolyte and pH balance.

In addition, potassium also helps regulate the adrenal hormones, particularly aldosterone.

Much like the other electrolytes, I have found that a vast majority of my patients are deficient in potassium. The reference range for potassium is 3.5 to 5.3 mmol/L. However, the optimal range is from 4.5 to 5.0 mmol/L.

This reference range is drawn from the serum, meaning that it is a measure of extracellular potassium. But remember, most potassium is found inside the cells.

To better assess potassium levels, I suggest getting a measure of red blood cell potassium. The range for red blood cell potassium is 90 to 111 mmol/L with an optimal level greater than 100 mmol/L.

Patients taking diuretics are often deficient in potassium, and are frequently prescribed potassium pills with the diuretic medication.

Potassium deficiencies can also be common in patients who suffer with diarrhea or very loose stools. Too much potassium can occur in patients with kidney failure and result in arrhythmias that can lead to death.