Okay, exhale. I'm not planning to spell out all 300 -- but that's how many vital bodily functions require this mighty mineral: magnesium. Yet three out of four of us don't get as much magnesium as we need, according to Elizabeth Somer, RD, author of The Essential Guide to Vitamins and Minerals. So there's a 75% chance that you're low on it, yet you've probably never given the mineral a second thought. Why? Partly because magnesium just isn't a headline grabber -- yet -- like calcium, folic acid, and iron. But it should be. Here are seven key reasons why getting enough is so important. (We'll save the other 293 for another day).
Magnesium helps you cope with stress. Stress hormones drain magnesium from the body, and low magnesium raises stress hormones. In this chicken-and-egg situation, getting enough gives you an edge in both directions.
It keeps your blood pressure healthy. Magnesium works with sodium, calcium, potassium, and other minerals to help regulate blood pressure.
It helps curb PMS. During the last two weeks of the menstrual cycle, magnesium levels drop, which can contribute to water retention, cramping, headaches, and an oversensitive nervous system. Getting 320 milligrams (mg) of the mineral a day could help counter these problems.
It cuts your diabetes risk by a third. Shortages can lead to insulin resistance, a condition that sends your blood sugar soaring, which is almost an engraved invitation for diabetes.
It's a must for sturdy bones. More than 50% of your body's magnesium is in your bones. Shortages disturb the calcium balance and bone metabolism, raising your risk of osteoporosis.
It could spare you a heart attack. Research suggests that magnesium reduces the formation of artery-blocking blood clots.
And it may prevent painful gallstones. Magnesium deficiency boosts bad triglycerides and lowers good HDL cholesterol -- both encourage cholesterol-filled gallstones.
So, how much do you need . . . and how do you get it?

Women need about 320 mg of magnesium a day; men, about 420 mg. Here's an example of all it takes to get that much from a day's worth of eating:
For women:
1 glass of soymilk for breakfast
2 slices of 100% whole-wheat bread on your lunch sandwich
1 palmful of almonds for an afternoon snack
1/2 cup of brown rice and 2 cups of spinach salad for dinner
For men:
Same menu as above, but add 2/3 of a cup of kidney beans to dinner.
Other good daily food sources of magnesium include nuts in general, oatmeal, shredded wheat, wheat bran, bran flakes . . . hmm, notice a trend here? Yes, whole grains are a spiffy source of magnesium -- and there's a bonus: Eating 6 servings of whole grains a day can make your RealAge as much as 4 years younger. Nice.