The best sources of magnesium to help support regular exercise

Posted by for Strength

A dietician explains the best sources of magnesium to eat to support your muscles and bones. 

If you exercise regularly then you probably already know that you need to be drinking enough water, fuelling with enough carbohydrates and recovering with enough protein. But have you thought about the smaller micronutrients too? You should be, according to studies, that show strenuous exercise apparently increases urinary and sweat losses that may increase magnesium requirements by 10-20%.

That’s because magnesium is involved in processes that affect muscle function including oxygen uptake, energy production and electrolyte balance – all essential processes when working out. 

“Magnesium is an essential mineral,” says registered dietician Tai Ibitoye. Tai explains that, in addition to the above processes, magnesium “is crucial for muscle and nerve function, to regulate blood glucose and blood pressure levels and for healthy bones.”

Worryingly, one in nine women may be falling below the Lower Reference Nutrient Intake when it comes to their magnesium intake, according to the nutrition society. But what does this mean?  


It’s important to differentiate between low levels (less than optimal), of nutrients and deficiency, (serious implications). As with other vitamins, it is hard to tell if your magnesium levels are low until you are severely deficient, Tai says, and you’ll need a blood test to find out. However, some symptoms to look out for may include:

  • Muscle weakness
  • Muscle cramps
  • Vascular dysfunction, showing as an irregular heart beat 
Magnesium sources
Spinach and salmon are great sources of magnesium

“The average population should not be worrying about being deficient in magnesium,” explains Tai. “Those who are most at risk include people who are critically ill, people with alcohol dependency or who drink a lot or those who are very malnourished.”

As for those who do regular exercise, Tai says there needs to be more research into whether they are at risk of low levels of magnesium, but that generally they should be aware about the quality of their diet, “including what they are eating before and after exercise and having a balanced diet that includes a lot of sources of magnesium.”


“People can get all of the magnesium they need through a healthy and balanced diet,” says Tai. “So having a magnesium supplement is not really necessary.” In fact, many foods that are affordable and easy to include in your diet contain high levels of magnesium, such as:

  • Spinach (around 87mg of magnesium per 100g)
  • Nuts, especially almonds and cashews (between 70-80mg of magnesium per 30g serving)
  • Wholegrain bread (one slice contains around 23mg of magnesium)
  • Avocado (one medium avocado contains 56mg of magnesium)
  • Tofu (around 30mg per 100g)
  • Salmon (3oz contains around 30mg)
  • Banana (a medium banana contains around 30mg) 

Adult women should aim for around 270mg of magnesium a day. If you want to supplement, the NHS advises against taking more than 400mg of magnesium a day, and it’s best to check with your GP if you are worried about magnesium levels before doing so. 

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Images: Getty / Unsplash 

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Chloe Gray

Chloe Gray is the senior writer for's fitness brand Strong Women. When she's not writing or lifting weights, she's most likely found practicing handstands, sipping a gin and tonic or eating peanut butter straight out of the jar (not all at the same time).