EVIDENCE-BASED PRACTICAL ADVICE FOR ENDURANCE ATHLETES

Magnesium for girl power!

All athletes know (or should know) that nutrition is an important part of ensuring optimum muscle mass. Exercise breaks down muscle tissue, which is repaired and rebuilt during recovery – providing sufficient protein is available. But while many athletes focus on protein, research shows that – for girls at least – the mineral magnesium could play an important role too.

In one recent study, researchers examined the relationship between magnesium intake, muscle mass and strength in 2,570 women aged between 18-79 years(1). All the subjects underwent DXA scanning – a highly accurate method of measuring bone mass, fat mass and muscle mass – and had their average magnesium intake assessed using food frequency questionnaires and dietary records. Strength was assessed using tests to measure leg explosive power and grip strength, Blood tests were also carried out to measure levels of a marker of inflammation called ‘CRP’; higher levels of CRP are associated with chronic low-grade inflammation in the body, and lower levels of muscle mass.

The main findings were as follows:

  • Higher intakes of magnesium were associated with higher levels of muscle mass. Compared to the lowest 20%, women in the top 20% of magnesium intake had around 3% more lean muscle mass;
  • Higher intakes of magnesium were also associated with greater strength levels – around 20 watts extra in the leg strength test by women in the top 20% of magnesium intake compared to the bottom 20%;
  • CRP levels were reduced by higher magnesium intakes, especially in women over 50;
  • Magnesium intake was a far better predictor of strength and power than the women’s protein intake (a nutrient more usually associated with higher levels of muscle mass and strength).
  • The researchers concluded that dietary magnesium could be effective at helping to maintain skeletal muscle mass and power in women of all ages.

What does this mean?

First off, let’s add the caveat that discovering an association in science isn’t the same as proving cause and effect. Given that unprocessed foods such as vegetables and whole grain are better sources of magnesium than processed foods, it might be that the women with higher magnesium intakes simply had healthier lifestyles generally. On the other hand, the large number of subjects used and the fact there was also a link with CRP suggests these results should be taken seriously. Also, some other recent studies have found an association between magnesium intake and strength in athletes(2,3). And given the importance of magnesium in energy production, all athletes (but especially female athletes) should pay attention to their magnesium intake. If you’re an endurance athlete, but especially a female endurance athlete, you should therefore:

  • Ensure you use whole grain breads and cereals rather than white, refined products;
  • Consume green leafy veg regularly.
  • Consume nuts and seeds (as snacks or in salads), which are not only rich in magnesium, but an excellent source of essential fats;
  • Consider taking a regular magnesium supplement (100mg in the morning and again at night is a good starting point).
  1. J Bone Miner Res. 2016 Feb;31(2):317-25
  2. Magnes Res. 2011 Dec;24(4):215-9
  3. Magnes Res. 2010 Sep;23(3):138-41

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