In the hot days ahead with outdoorsy activities, potassium depletion is something to watch. Spinach, chard and Crimini mushrooms great sources of the mineral needed for good muscle function - and that means your heart!
Here's a chart to show good sources for potassium
http://www.whfoods.com/genpage.php?tname=nutrient&dbid=90And here's some info form that site:
"What is the function of potassium?
Muscle contraction and nerve transmission
Potassium plays an important role in muscle contraction and nerve transmission. Many of our muscle and nerve cells have specialized channels for moving potassium in and out of the cell. Sometimes potassium moves freely in and out, and sometimes a special energy-driven pump is required. When the movement of potassium is blocked, or when potassium is deficient in the diet, activity of both muscles and nerves can become compromised.
Other roles for potassium
Potassium is involved in the storage of carbohydrates for use by muscles as fuel. It is also important in maintaining the body’s proper electrolyte and acid-base (pH) balance. Potassium may also counteract the increased urinary calcium loss caused by the high-salt diets typical of most Americans, thus helping to prevent bones from thinning out at a fast rate."
Scroll in the page for toxicity symptoms, too. Too much isn't good either.