— Karen Gotleib, Toronto
A: Calf cramping at night can be as puzzling as it is painful. No one is really sure why leg muscles spasm in the dark, but at least the list of suspects is relatively short—and you've already ruled out dehydration.
Your muscles rely in part on several minerals to contract; these include potassium, calcium, and magnesium. If you're deficient in any of them, the excitability of nerve endings—and the muscles they stimulate—increases, which can trigger cramps. To bump up your intake of potassium, try eating more low-fat yogurt, spinach, beans, and lentils. Bananas, bran cereal, brown rice, and almonds are all good sources of magnesium. And you can boost calcium with low-fat or nonfat dairy foods.
Other causes include extreme physical exertion during the day, which can lead to the depletion of glycogen (fuel for muscle cells) and leave muscles prone to cramping. You can address this by easing back slightly on your exercise.
Less common suspects are thyroid disease and some medications for asthma, high blood pressure, and heart disease. If you don't find the culprit on the short list, engage your doctor's help to expand the search. With some diligence, you're almost sure to find an answer and relief.