Magnesium strengthens bones; maintains nerve and muscle function; regulates heart rhythm and blood sugar levels; and helps maintain joint cartilage.

How Much: Recommended dietary allowance (RDA) = 420 milligrams (mg) daily for men 31 and older; 320 mg for women. For best absorption, choose magnesium orotate, oxide or citrate.

Too Much: Tolerable upper limit (UL) = 350 mg.

Too Little: Rare, but early symptoms include loss of appetite, nausea, vomiting, fatigue and weakness.

Foods: Almonds, cashews, peanuts and peanut butter; soybeans; spinach; dried beans; potatoes; and whole grains.

Interactions: Some diuretics, antibiotics, antacids and laxatives. 

Research Note: Many studies, including the Framingham Heart Study, have found that eating foods high in magnesium and potassium increases bone density and may help prevent postmenopausal osteoporosis.