The importance of vitamins and nutrients are under valued when it comes to someones daily regime.  People often get caught up in eating low fat high protein meals that they often forget how critical it is to consume the recommended daily intake of vitamins and minerals.  The body needs these in certain amounts to function optimally,  to metabolize food into energy, boost energy and improve immune function among other things.  Key functions of the element  Magnesium are:

normal nerve and muscle function, support a healthy immune system, keep the heart beat steady, and assists in keeping bones strong. It also helps regulate blood glucose levels and aid in the production of energy and protein. There is ongoing research into the role of magnesium in preventing and managing disorders such as high blood pressure, heart disease, and diabetes.  Just like everything else with the human body we are constantly learning more and more about it.  One thing we know for sure is that we need Magnesium at these Recommended Dietary Allowances:

14–18 years 410 mg 360 mg
19–30 years 400 mg 310 mg
31–50 years 420 mg 320 mg
51+ years 420 mg 320 mg

Sources of Magnesium in Milligrams (mg) per serving :

Almonds, dry roasted  1 ounce 80mg, Spinach boiled ½ cup 78mg, Cashews  dry roasted  1 ounce 74 mg, Peanuts oil roasted ¼ cup 63mg, Soy milk plain or vanilla 1 cup 61mg, Black beans, cooked ½ cup 60mg, Edamame shelled, cooked ½ cup 50mg, Peanut butter  2 tablespoons 49mg, Bread whole wheat 2 slices 46mg, Avocado 1 cup 44mg, Potato baked with skin 3.5 ounces 43mg, Rice brown, cooked ½ cup 42mg, Yogurt, plain low fat 8 ounces 42mg, Kidney beans canned ½ cup 35mg, Banana, 1 medium 32mg Halibut, cooked 3 ounces 24mg, Raisins, ½ cup 23mg, Chicken breast, roasted 3 ounces 22mg, Beef, ground 90% lean, pan broiled, 3 ounces 20mg, Broccoli, chopped and cooked ½ cup 12mg,  Rice, white, cooked, ½ cup 10mg, Apple, 1 medium 9 mg, Carrot, raw 1 medium 7mg.

The list goes on and on however the foods listed above are just several common foods found in ones kitchen.  If you have a deficiency taking a multivitamin everyday will aid you in topping up your vitamin and mineral levels.