Magnesium isn’t very exciting, but it’s one of the few dietary supplements that I regularly recommend. It won’t make you gain pounds of muscle mass, yet it’s incredibly important. Especially knowing that strength athletes often quickly run into a magnesium deficiency.
Table of Contents
The role of magnesium
Magnesium is a mineral and essential for the body. Magnesium plays an important role in normal nerve and muscle function. It is involved in muscle relaxation, while calcium is involved in muscle contraction.
Once your muscles receive the signal from the nervous system to contract, a lot of calcium is released into the muscle cells. As a result, the muscles contract. You can compare this contraction to pulling yourself up on a rope. Calcium helps you grip and pull up. To go higher, you need to let go to be able to grip higher again. Magnesium (along with ATP) facilitates this ‘letting go’. The exact mechanism of calcium and magnesium in muscle contraction and relaxation is of course more complex and can be found in an older article on the functioning of muscles.
So, there is an interaction between calcium and magnesium.
Symptoms of magnesium deficiency and excess
If your magnesium level is too low, you may experience muscle cramps, general fatigue, and even heart rhythm disorders in extreme cases. These are things you don’t want. You also don’t want too much magnesium, as it can lead to low blood pressure and disturbed breathing [3, 8].
Chronic sleep deprivation can cause a magnesium deficiency and therefore reduced exercise tolerance [10]. In other words, you may perform less well in the gym. Sufficient (not too little, not too much) magnesium can improve the quality of your sleep and thereby increase your exercise tolerance [9].
So, as with any nutrient, the key is to find the balance.
How much magnesium do I need?
The body contains about 25 grams of magnesium [1]. Magnesium is mainly found in your bones, teeth, and muscles. Not in your blood.
The recommended daily amount of magnesium is about 6 mg per kilogram of body weight per day [2]. For men, this is about 300 to 400 mg per day, for women it’s around 300 to 250 mg [1, 3].
Athletes need 10 to 20 percent more than inactive individuals. This is because exercise involves sweating and more frequent urination, resulting in magnesium loss [5].
Let’s say you’re an 80 kg man who does strength training, then you need about 580 mg of magnesium per day according to the above guidelines. (80 * 6) + 20% = 580 mg
Am I getting enough?
According to the Dutch Nutrition Center and the Vitamin Information Bureau, the average person gets enough magnesium [3, 11]. According to an American study, this is not the case. The study involved 8437 people and found that approximately 50% had a magnesium deficiency [4].
Let’s take the example again of the 80 kg man who does strength training. We’ll call him Bob. Meet Bob:
Bob needs about 580 mg per day. He wants to maintain the same weight and therefore consumes 2500 kcal per day (calculated according to the Harris Benedict formula). He fills this with a typical Dutch/athlete’s diet. Brinta, bread, chicken, fruit, vegetables, etc…
| Product | Quantity | Kcal | Proteins | Carbohydrates | Fats | Magnesium |
| Brinta | 100 grams | 366 | 12 | 74 | 3 | 80 |
| Milk (semi-skimmed) | 500 ml | 250 | 18 | 25 | 8 | 55 |
| Bread | 4 slices | 336 | 12 | 64 | 3 | 80 |
| Peanut butter | 40 grams | 248 | 8 | 6 | 22 | 64 |
| Chicken breast | 150 grams | 167 | 32 | 0 | 5 | 45 |
| Olive oil | 15 ml | 123 | 0 | 0 | 14 | 0 |
| Rice | 100 grams | 347 | 7 | 79 | 1 | 12 |
| Apple | 1 piece | 60 | 1 | 14 | 0 | 5 |
| Broccoli | 200 grams | 200 | 40 | 4 | 6 | 40 |
| Quark | 500 grams | 310 | 45 | 30 | 1 | 50 |
| Walnuts | 40 grams | 264 | 6 | 3 | 25 | 60 |
| Kiwi | 1 piece | 24 | 0 | 6 | 0 | 5 |
| Total | 2535 | 144 | 307 | 80 | 500 |
With this diet, he gets 500 mg of magnesium per day, not bad! Bob’s RDA was 580 mg, so he’s just below it.
It’s important to mention that I’ve calculated how much Bob is getting in the above diet. How much is actually absorbed is another story. There are indications that calcium can interfere with magnesium absorption [6, 7]. So, Bob may be getting even less.
What you should also realize is that Bob is currently eating at maintenance level. If he wants to lose weight, he’ll need to reduce his calories and therefore cut things from his diet. These will likely be grains (brinta and bread), which are rich in magnesium. This means he’s more likely to develop a deficiency.
So, while it’s certainly possible to get enough magnesium from your diet, it’s difficult. Especially if you want to lose weight, the chances are very high that you’ll get too little. This is because magnesium is mainly found in carbohydrate-rich products like grains. Which are precisely the products you cut first when you want to lose weight.
Magnesium supplementation is therefore often recommended during weight loss.
Which type and how much you should take will be discussed in the next article. Spoiler alert: The type of magnesium used in multivitamins is 99 out of 100 times not the one you want
References
- nap.edu/read/5776/chapter/8
- Durlach J. Recommended dietary amounts: Mg RDA. Magnes Res. 1989
Sep;2(3):195-203. Review. PubMed PMID: 2701269. - voedingscentrum.nl/encyclopedie/magnesium.aspx
- ars.usda.gov/ARSUserFiles/80400530/pdf/0506/usual_nutrient_intake_vitD_ca_phos_mg_2005-06.pdf
- Nielsen FH, Lukaski HC.
- Hardwick LL, Jones MR, Brautbar N, Lee DB.
- merckmanual.nl/mmhenl/sec12/ch155/ch155g.html
- Abbasi B, Kimiagar M, Sadeghniiat K, Shirazi MM, Hedayati M, Rashidkhani B.
- Tanabe K, Yamamoto A, Suzuki N, Osada N, Yokoyama Y, Samejima H, Seki A, Oya
M, Murabayashi T, Nakayama M, Yamamoto M, Omiya K, Itoh H, Murayama - vitamine-info.nl/alle-vitamines-en-mineralen-op-een-rij/magnesium/
