What is the role of magnesium in managing atrial fibrillation?
When a patient goes online and searches about magnesium and AFib, they will find an abundance of information on its use. There are several web pages promoting magnesium use as a natural treatment for atrial fibrillation in addition to promoting several over the counter supplements for magnesium. But what does the data show? Is there any medical literature that says magnesium is beneficial for atrial fibrillation?
Magnesium deficiency is common, as most people in the United States do not eat enough magnesium in their daily diet. Magnesium is a important mineral that is involved in the coordination of a natural heartbeat, and is a key component of the energy molecules needed to keep your heart beating strong. About 99% of total body magnesium is located in bone, muscles and non-muscular soft tissue, whereas only a small amount (1%) is located in your bloodstream at any time. However, when being tested for a magnesium deficiency, the blood concentration is what is usually tested.
So does magnesium deficiency lead to AFib? The long-term answer is still being studied, but there has been some research that suggests the two may be related. In a 2013 study, as part of the Framingham Heart Study, over 3,500 patients were followed over 20 years. In this study, individuals in the lowest quartile of serum magnesium were ~50% more likely to develop AF compared with those in the upper quartiles. In another study from 2016, An HMO database showed that an increased AFib risk was associated with mild and moderate decreased serum magnesium levels.
There is certainly data showing a link between low magnesium levels and the risk of AFib, but is there data showing that supplementing magnesium will decrease risk or improve AFib? The simple answer is no.
There have been no long-term clinical trials to date that demonstrate replacing magnesium reduces or reverses atrial fibrillation.
This means that there are no clinical studies at this time that have shown that people who take magnesium supplements for years have improved their AFib. The research to date has been associated with short-term management of AFib, usually in the hospital or in relation to heart surgery.
The majority of studies involved with magnesium and atrial fibrillation look at patients who are undergoing heart surgery. Episodes of atrial fibrillation are a significant concern for patients who undergo open-heart surgery, as it can significantly prolong a patient’s hospitalization and recovery after surgery. There have been over 10 studies published over the years about giving magnesium supplementation prior to heart surgery, and there is still no clear consensus on its effectiveness. (Some studies say it helps, others say it does not help.)
In addition, there are several studies that have looked into the use of magnesium infusion in the emergency room or during a hospital stay. It has been found that intravenous magnesium can help slow the heart rate down when it is going too fast during an AFib episode. Magnesium can also help with the conversion of AFib back to normal rhythm and can improve the success rate of a cardioversion, especially when using in combination with anti-arrhythmic heart medications.
Since the majority of a person’s magnesium is inside your cells and isn’t accounted for in a blood test, there are several available methods that can test for a deficiency in total body magnesium, which in theory would be more accurate way to test for magnesium deficiency. However, these types of studies are typically not covered by insurance, and may end up costing a patient several of hundreds of dollars out of pocket. There is also no clinical data that supports this type of expensive testing is more beneficial to a patient than a simple serum deficiency test.
What is the best way to supplement magnesium deficiency?
There are over 10 types of magnesium supplements available, many of which are advertised directly to heart patients to help them manage their AFib and other heart arrhythmias. There appears to be a lot of variability between the different supplements and the how much magnesium is actually absorbed, but do they actually help with AFib? Like any over the counter supplement, they are not as strictly monitored by the FDA and there is no clear clinical trial data that shows any particular supplement or brand of supplement reduces the amount of AFib a patient has.
So what do I recommend to my patients? First, for any patient with atrial fibrillation it is important to routinely check magnesium level. I routinely check a serum magnesium level, because it is readily available and typically covered by patient’s insurance. Despite theoretical advantages, I do not routinely test for intracellular magnesium due to higher out of pocket costs to patients, and the fact that there has been no clear clinical trial data looking at intracellular magnesium and risk for atrial fibrillation.
If you are found to be magnesium deficient, consider supplementing your diet with foods that are high in magnesium. This includes dark green vegetables, avocados, bananas, legumes, nuts and fatty fish, just to name a few. Another option to increase your magnesium level is to take over the counter supplements. I typically start with magnesium oxide because it is widely available in most drug stores and is typically well tolerated. However, there is a wide range of supplements available, and I have seen several patients benefit from magnesium glycinate and magnesium taurate. Discuss with your doctor which supplement would be correct for you.