Are you getting your 320 mg of magnesium per day
(for men, that's 420 mg/day)? If you're way under that limit, it could explain why you feel so depleted after walking upstairs to the copy machine. Magnesium is critical for processes like energy metabolism, and research nutritionist Forrest H. Nielsen, PhD, has found that magnesium deficiencies can make physical activity feel much more taxing than it should. Almonds, cashews, peanuts, pumpkin seeds and sunflower seeds are all terrific sources—and conveniently, are often packaged together.