I have been thinking a lot about magnesium (Mg) lately. Not because I am a geeky scientist (I have a PhD in Chemistry), but because I have been experiencing foot and calf cramps during and after training sessions. Two things happened that led me to magnesium. As Beth my Crew Chief often does, she struck up conversation with a lady that looked like an athlete in the grocery store check-out line. Turns out the lady is a serious runner. Beth mentioned my calf problems and the lady immediately said I should be taking a Mg supplement because I train in the hot Texas summer. The second Mg clue I got was at Ironman Vineman last July. As I was going through my “swag” bag, I found a little packet from MgSport® containing magnesium capsules to prevent leg cramps. I thought I should do some research.
Why is Magnesium Important?
A quick google search tells us that magnesium plays a number of critical roles in our bodies. From the Livestrong website: “Magnesium serves many functions in the body. One of the more important functions is for contracting and relaxing muscles, but this mineral is also essential to transporting energy, maintaining the immune system and strengthening the bones, to name only a few.” There is much more information available that I won’t go into here. Let’s just say, it is one of those things the body just can’t do without.
Does a Magnesium Deficiency Cause Muscle Cramps?
In my limited research, I found several references indicating that low magnesium in the body can contribute to muscle cramps. An article from the Mayo Clinic website states: “Too little potassium, calcium or magnesium in your diet can contribute to leg cramps.” From the Livestrong website, an article on electrolytes states: “A common cause of leg cramps is a deficiency in some kind of electrolytic mineral, oftentimes potassium or magnesium.” Other articles made similar claims.
What are the Causes of a Magnesium Deficiency?
While I won’t get into any medical conditions that could result in a deficiency, I’ll focus on a couple of things that contribute to low magnesium levels in healthy individuals, including endurance athletes. First, magnesium is not produced in the body so we have to get it from food or other sources (e.g. supplements). The problem is, the diets of many of us don’t include foods that are high in Mg; therefore, we often don’t get enough in our daily intake to satisfy our body’s requirements. Foods that are high in Mg include: dark-green vegetables, legumes, whole grains, nuts, seeds and fish. If you are not eating foods like these, you are probably not getting enough Mg.
A second contributor to low magnesium levels (and particularly applicable to us endurance athletes) is loss of magnesium through sweat. Mg is similar to other electrolytes in our body like sodium and calcium. When we sweat, we lose them. Some, but not all electrolyte replenishment products contain Mg; however, it is typically not nearly at daily recommended intake levels.
Let’s Talk a Little Chemistry and Biology
The element of magnesium does not exist naturally on its own. It must be bound to another substance to be stable in nature. So there are various forms of magnesium depending on what it is bound to. For example, it can be bound to oxygen to form magnesium oxide or to chlorine to form magnesium chloride. Some forms such as magnesium citrate, lactate, and gluconate are collectively known as chelated magnesium, which simply means that one molecule of the citrate, etc. is doubly bound to the magnesium. Depending on what it is bound to, the magnesium substance will have different properties. For example one form may dissolve better in water than another form. I will come back to this when I talk about supplements.
Once magnesium is in our body, it has to be absorbed and circulated so that it can do its thing. Some forms of magnesium are broken down, absorbed, and circulated better than other forms; therefore, more of the magnesium is available to do the work. This is known in the science world by the technical term “bioavailability.” In addition to getting into our body and circulating, the magnesium needs to find its way into the cells within our body. This is where the magic of magnesium happens. Again, I will come back to this when I talk about supplements.
Do Magnesium Supplements help Prevent Muscle Cramps?
According to the scientific literature, this is up for debate. In my limited search, I found a few studies addressing the question. In one review, there was a discussion of four studies on older adults. Unfortunately, none of these studies included data on cramps associated with exercising. The review concluded that magnesium supplementation did not provide a benefit for cramping.
In my opinion, additional studies are needed. Muscle cramps are not solely caused by lack of magnesium. We know that depletion of other electrolytes (e.g. sodium and potassium) also contribute to muscle cramps. These electrolytes work together; therefore, if you supplement one but your body is depleted of the others, you will likely still get cramps. I would like to see studies on endurance athletes that would include evaluating subjects that have sufficient electrolytes such as sodium and potassium, and compare subjects that have and have not been supplemented with magnesium. I believe that would provide a better picture of the effectiveness of magnesium supplements for cramping.
Here is the one data point I have: My leg and foot cramping has dramatically improved since I started taking a magnesium supplement.
Are all Magnesium Supplements the Same?
The short answer is no. Recall the science lesson above. Supplements are available in several forms including magnesium bound to: citrate, lactate, oxide, and gluconate to name a few. Some supplements contain additional components such as Vitamins B6, D, and E in the formulation. The different forms and formulations are designed to address bioavailability and absorption into the body’s cells.
There are several studies comparing uptake of various magnesium forms in the body. Studies that looked at bioavailability generally concluded that magnesium oxide has low bioavailability and the chelated forms such as citrate and lactate have higher bioavailability. These studies generally looked at magnesium levels in the blood stream or the amount excreted in urine. One interesting study compared magnesium levels within cells (intracellular magnesium) when subjects took either magnesium oxide or magnesium citrate. The study showed the oxide form increased intracellular magnesium levels when compared to the citrate form. So while citrate appears to be more bioavailable, this study suggests that the oxide form is better at reaching the cells.
Another consideration with the various forms of magnesium supplements is the body’s tolerance for the substance. Some forms may cause an individual to have an upset stomach, for example. Magnesium also can act as a laxative, and some forms may trigger that effect more than others. Not the effect you need during your next long training run. The Crew Chief has been taking Mg supplements for a while now (even before I had my epiphany). She had some stomach problems with a Mg citrate supplement but she has been able to take a different chelated form without issues. She recently tried some of my MgSport (an oxide formulation) and she seems to prefer it over the others that she has tried.
A Plug for MgSport
MgSport is a magnesium supplement that uses the oxide form as the magnesium source. Vitamins B6, D, and E are also added to the formulation. The concept of the formulation is that the added vitamin materials help with absorption and make the Mg oxide more bioavailable. From the science lesson, we learned that the oxide form typically has low bioavailability. However, the oxide form is more effective in getting into the cell, according to at least one study. So the MgSport product theoretically gets more magnesium into the system and ultimately into the cells. Additional information is available at their website here.
After trying out the free packet of MgSport from my “swag” bag, I ordered a 100-count bottle of capsules from Amazon. I have been taking the prescribed one capsule each night before bed. Training in Texas is hot for much of the year, and I sweat a lot. I have a routine of taking on an electrolyte drink, and I also use BASE salts (BASE Performance) during long runs and rides. My cramping problems usually occur after workouts, at night in bed, and often in the pool while swimming long sets. Since I added MgSport to my daily routine, my cramps have essentially been eliminated.
What is your Experience with Magnesium?
I would be interested in hearing about your experiences with magnesium supplements and cramping. Do you feel that they work? Which supplements have you tried?