Physician Resources

Patient Handout: Magnesium and irregular heart beats

A number of my patients have trouble with irregular heart beats. It can be very common and is people call this many different things. Some feel they are having “skipped beats” or a “flip-flop” of the heart. Many will call these palpitations and it is best described as a feeling that the heart has jumped or beaten out of sequence.

While a lot of people have skipped beats many will not feel them and only know because their doctor told of it. For the most part the irregular beats are benign and are the effect of an early beat from the heart’s ventricle or atrium. If it is from the ventricle we call this a Premature Ventricular Contraction (PVC). As you might expect, beats that originate in the atrium are Premature Atrial Contractions (PAC).

There can be a number of causes and there are many much more serious problems with heart rhythms. It has been shown that magnesium may play a role in premature beats such as PACs and PVCs. In an effort to see if a diet low in magnesium might contribute to an increase in early heart beats researchers at the USDA Agricultural Research Service studied 22 post-menopausal women by asking them to eat a diet that was designed to be low in magnesium (Am J Clin Nutr 2002;75:550-4).

The women were divided into two groups. One group was fed a diet that contained less than half of the Recommended Daily Allowance of magnesium (this is 320 mg for women and 400 mg for men). The other group consumed a diet that was supplemented with magnesium. Each group ate their diet for 81 days and then they switched to the other diet (researchers call this a “crossover” design).

Blood tests were taken to measure magnesium and heart rhythms recorded using a device that the participants wore for up to 21 hours at a time. While their blood tests didn’t show a decrease in magnesium levels when the women were on the low magnesium diet they had many more early heart beats documented by the monitor.

The researchers suggested that those who may not get enough magnesium in their diets, or those taking diuretics, may want to supplement with magnesium. There is a feeling that those in areas with a supply of soft water may also experience a decrease in their intake of magnesium.

What this means for you: If you are having skipped beats, palpitations or any type of heart racing, check with your doctor. It is not likely serious. You and your physician may want to discuss supplements, but the best way to get magnesium in your diet is one that it rich in legumes, nuts, fruits, veggies and fish. Here’s a list of the amounts of magnesium in some foods.

Common foods and the amounts of magnesium in milligrams (mg)

FOOD Serving size Milligrams (mg)
Halibut, cooked 3 ounces 90
Tuna 3 ounces 54
Almonds, dry roasted 1 ounce 80
Cashews, dry roasted 1 ounce 75
Nuts, mixed, dry roasted 1 ounce 65
Bran Flakes 3/4 cup 40
Cereal, shredded wheat 2 rectangular biscuits 55
Oatmeal, instant, fortified, prepared w/ water, 1 cup 55
Bread, whole wheat, commercially prepared, 1 slice 25
Potato, baked w/ skin 1 medium 50
Rice, brown, long-grained, cooked 1/2 cup 40
Soybeans, mature, cooked, 1/2 cup 75
Peanuts, dry roasted 1 ounce 50
Peanut butter, smooth 2 Tablespoons 50
Blackeyed Peas, cooked 1/2 cup 45
Lentils, mature seeds, cooked 1/2 cup 35
Kidney Beans, canned 1/2 cup 35
Pinto Beans, cooked 1/2 cup 35
Yogurt, plain, skim milk 8 fluid ounces 45
Wheat Germ 2 Tablespoons 35
Milk, reduced fat (2%) or fat free 1 cup 27
Whole Milk 1 cup 24
Chocolate Pudding 4 ounce ready-to-eat portion 24
Banana, raw 1 medium 30
Dried Figs 4 figs 44
Raisins, seedless 1/4 cup packed 25
Avocado, California 1/2 cup 35
Artichokes 1 cup 101
Broccoli 1 cup 37
Parsnips 1 cup 45
Yellow Squash 1 cup 43
Spinach, frozen, cooked 1/2 cup 75