(Reuters Health) - Magnesium supplements taken daily for three months may result in slightly lower blood pressure, according to an analysis of more than 30 existing studies.
Previous evidence has suggested that magnesium deficiency may be related to cardiometabolic disorders, including high blood pressure, said lead author Yiqing Song.
“Taking oral magnesium supplements regularly can help lower blood pressure and can be considered as an inexpensive, safe, and adjuvant antihypertensive therapy,” said Song, of the Richard M. Fairbanks School of Public Health at Indiana University in Indianapolis.
But magnesium supplements can cause gastrointestinal symptoms, and may interfere with medications, he told Reuters Health by email.
“Patients with heart disease, kidney disease, liver disease or other critically ill conditions should not take magnesium supplements without their doctor’s consent and supervision,” Song added.
The researchers combined data from 34 clinical trials that included a total of more than 2,000 people. Based on those results, they found that taking daily supplements of about 368 milligrams of magnesium for about three months seemed to reduce blood pressure measurements by between one and two millimeters of mercury (mm Hg).
Normal blood pressure readings are 120 mm Hg systolic (the top number) or less, and 80 mm Hg diastolic (the bottom number) or less. Hypertension, or high blood pressure, is usually defined as a systolic reading of 140/90 mm Hg or higher.
About 70 million adults in the U.S., or one in three, have high blood pressure, according to the Centers for Disease Control and Prevention.
Finding safe ways to lower blood pressure, even modestly, could have significant public health impact, the study authors write in Hypertension.
People taking these supplements also had higher levels of magnesium in their blood than those taking placebo, which suggests - but doesn’t prove - that the magnesium is responsible for the slight lowering of blood pressure readings in the group taking the supplements.
The U.S. Recommended Dietary Allowance for magnesium is 310 to 320 milligrams per day for women and 400 to 420 mg per day for men. Half a cup of boiled spinach contains almost 80 mg of magnesium, and beans, nuts and other leafy greens are also good sources of the mineral.
People can get as much magnesium as in the supplements in these studies from adhering to a healthy diet, American Heart Association spokesperson Penny Kris-Etherton said in a statement.
“This study underscores the importance of consuming a healthy diet that provides the recommended amount of magnesium as a strategy for helping to control blood pressure,” said Kris-Etherton, a distinguished professor of nutrition at the University of Pennsylvania in Philadelphia who was not part of the analysis.
The supplements were well-tolerated, Song said, but some people experienced non-serious side effects like mild abdominal pain, diarrhea, soft stool, nausea, and vomiting.
It’s still not clear how magnesium lowers blood pressure, he noted.
SOURCE: bit.ly/29Em2BY Hypertension, online July 11, 2016.