Friday, September 27, 2019

Magnesium Supplements For Muscle Cramps?

Available from my local pharmacy
A patient came in today saying she went to a local running store and was advised to take some magnesium supplements as she cramps occasionally while racing. So she went ahead and bought some. She wanted my thoughts on whether they truly work since they seem to be the latest "silver bullet" that most runners seem to be taking.

Magnesium is an essential nutrient that's actually found in many of the foods we're already eating. It is actually abundant in our bodies. Our bodies need it to create new proteins, for energy production in cells, DNA synthesis etc. As it is essential, our bodies store it in our bones, where it can easily be accessed if needed. Since our bodies cannot produce it, we need to get it from our diet.

An adequate magnesium is needed for a healthy pregnancy and to produce enough milk after giving birth. It is also useful if you take diuretic drugs, proton pump inhibitors and if you're diabetic.

It is suggested that adults need 300-400 milligrams a day and you will get enough if you eat enough legumes (chickpeas, black and kidney beans), nuts, seeds, veggies (broccoli, cabbage, asparagus, kale and spinach), fatty fish (tuna, salmon and mackerel) and some fruits (avocado, bananas, figs, guava and raspberries).

It is estimated that 10-30 percent of people in developed countries may have a mild deficiency in magnesium (DiNicolantonio et al, 2018). Severe deficiencies are uncommon but easy to spot. Symptoms include loss of appetite, vomiting and fatigue and following that numbness, muscle cramps, seizures, personality changes and heart artery changes if the deficiency continues.

It is why those who sell these supplements tell athletes to take them - to prevent muscle cramps! But note that the muscle cramps are preceded by loss of your appetite, vomiting and fatigue. Not the muscle cramps when you're training hard or racing. Note that the muscle cramps that occur when you have a magnesium deficiency happens with activities of daily living (not while exercising/ racing). Not only the muscles in your feet and legs cramp, but also your facial and masticatory (chewing) muscles.

Those who sell magnesium tablets, body sprays, serum and bath salts will tell you their products will boost recovery, energy levels and promote DNA synthesis, bone strength and other important body functions. When something sounds too good to be true, it probably is. If you eat a healthy diet of the food listed above that is rich in magnesium, then you wouldn't need any magnesium supplements.

You will not benefit from taking magnesium supplements unless you're deficient. This can only be verified via a blood test.

If you are lacking magnesium, you can either eat food sources rich in magnesium or take supplements. There is no evidence that any form of magnesium (whether it is magnesium oxide, aspartate or citrate) is more easily absorbed by our bodies. So don't buy the most expensive brand or version of it.

As for magnesium creams, oils, sprays, flakes and bath salts etc, evidence suggest that they are not as effective as claimed (Grober et al, 2017).

So if you have done a blood test and have a magnesium deficiency, load up on magnesium rich food or go ahead take a cheap supplement.

"So that means I wasted my money" went my patient? Now you know. And you've read what causes muscle cramps.


Grober U, Werner T et al (2017). Myth Or Reality- Transdermal Magnesium? Nutrients 9(8): 813. DOI: 10.3390/nu9080813.

DiNicolantonio JJ, O'Keefe JH et al (2018). Subclinical Magnesium Deficiency : A Principal Driver Of Cardiovascular Disease And A Public Health Crisis. Open Heart. 5:e000668. DOI: 10.1136/openhrt-2017-000668.

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