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Magnesium: Do you need a supplement?

Posted Feb. 27, 2012, at 1:33 p.m.

I had the radio on in my car the other day, and an advertisement came on for a magnesium supplement — I can’t say for sure whether the advertisement was for Magnesium Oxide 400 or Mag-Ox 400. Either way, this product that “promotes cardiovascular health” (statement not evaluated by the Food and Drug Administration, product not intended to diagnose, treat, cure or prevent any disease) appeared to be the “can’t live without supplement,” according to the advertisement. Of course I had to further evaluate this information.

Magnesium, the fourth most abundant mineral in the body, is essential to good health. Most of the magnesium is found in bone. It helps maintain normal muscle and nerve functions, keeps the heart rhythm steady, helps keep your immune system healthful and keeps bones strong. Magnesium also helps regulate blood sugar levels, promotes normal blood pressure and is known to be involved in energy metabolism and protein synthesis. More recently there has been an increased interest in the role of magnesium in preventing and managing disorders such as hypertension, cardiovascular disease and diabetes.

The recommended dietary allowance for magnesium for adults is 420 milligrams per day for men and 320 mg per day for women (more during pregnancy and lactation). The RDA for children varies from 80 to 360 mg depending on age and gender.

Surveys of dietary intake suggest that many Americans do not get the recommended amounts of the mineral, but symptoms of magnesium deficiency are rarely seen in the U.S. There is a concern that many people may not have high enough body stores of magnesium because their dietary intake is not high enough. This presents a problem because having enough body stores of magnesium may be protective against disorders such as cardiovascular disease and immune dysfunction. Magnesium is absorbed in the intestines and then transported through the blood to cells and tissues. About one-third to one-half of dietary magnesium consumed is absorbed into the body.

Healthful kidneys are able to limit urinary excretion of magnesium to make up for low dietary intake. However, excessive loss of magnesium in urine can be a side effect of some medications and can also occur in poorly controlled diabetes and alcohol abuse.

Early signs of magnesium deficiency include loss of appetite, nausea, vomiting, fatigue and weakness. As the deficiency state worsens, numbness, tingling, muscle contractions and cramps, seizures, personality changes, abnormal heart rhythms and coronary spasms can occur.

Magnesium supplementation may be indicated when a specific condition causes an excessive amount of magnesium to be lost or magnesium absorption is limited. Situations that may require magnesium supplementation include:

• Taking some medications including certain diuretics, antibiotics and medications used to treat cancer.

• Individuals with poorly controlled diabetes, as magnesium is lost in urine associated with hyperglycemia.

• Persons with alcoholism. Low blood levels of magnesium occur in 30 percent to 60 percent of alcoholics and in nearly 90 percent of patients experiencing alcohol withdrawal.

• Individuals with chronic malabsorptive problems such as Crohn’s disease and gluten-sensitive enteropathy.

• Older adults — magnesium absorption decreases and renal excretion of magnesium increases in older adults.

• Individuals with chronically low blood levels of potassium and calcium may have an underlying problem with magnesium deficiency.

When any of the above-mentioned medical conditions occur, don’t automatically start taking a supplement. Dietary magnesium does not pose a health risk, however, pharmacological doses of magnesium in supplements can promote adverse effects such as diarrhea and abdominal cramping. Instead have your doctor check your magnesium status to see if you need to increase your dietary intake of magnesium rich foods. Whenever possible it is recommended to get vitamins and minerals from foods rather than a supplement.

The best way to get extra magnesium is to eat a variety of whole grains, legumes and vegetables (especially dark-green, leafy vegetables) every day.

Selected food sources of magnesium

• Pumpkin or squash seed kernels, roasted, 1 oz., 151 mg

• Wheat bran, crude, ¼ cup, 89 mg

• Almonds, dry roasted, 1 ounce, 80 mg

• Spinach, frozen, cooked, ½ cup, 78 mg

• Raisin bran cereal, 1 cup, 77 mg

• Cashews, dry roasted, 1 ounce, 74 mg

• Wheat germ, crude, ¼ cup, 69 mg

• Nuts, mixed, dry roasted, 1 ounce, 64 mg

• Bran flakes, cereal, ¾ cup, 64 mg

• Shredded wheat, 2 biscuits, 61 mg

• Black beans, cooked, ½ cup, 60 mg

• Soybeans, green, cooked, ½ cup, 54 mg

• Lima beans, baby, cooked from frozen, ½ cup, 50 mg

• Beet greens, cooked, ½ cup, 49 mg

• Navy beans, cooked, ½ cup, 48 mg

Georgia Clark-Albert is a registered dietitian and adjunct nutrition instructor at Eastern Maine Community College who lives in Athens. Read more of her columns and post questions at bangordailynews.com or email her at GeorgiaMaineMSRDCDE@gmail.com.

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