The best magnesium supplements for post-run recovery – and when to take them

Magnesium is an essential mineral in any diet, but for runners it’s vital when it comes to post-training muscle recovery and in preventing muscle cramping.

This is because magnesium helps to regulate muscle and nerve function, blood sugar levels and blood pressure, with the body's requirements for magnesium going up the more active you are.

But before you even think about reaching for those magnesium supplements, it’s important to try to increase the amount of magnesium-rich foods in your diet. According to the NHS, the recommended daily intake for adults aged 19-64 is 300mg a day for men and 270mg a day for women. You should be able to get enough by eating a well balanced diet, particularly one that includes leafy greens, nuts, seeds and even dark chocolate (a good excuse, if you ask us).

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How can you tell if you’re getting enough magnesium?

One of the main signs that you might be low in magnesium is muscle cramping, says Renee McGregor, a leading sports dietitian. This is because magnesium plays an important role in muscle contraction. 'Particularly if you get cramps in the middle of the night – that does seem to be linked to low magnesium levels,' she adds.

Another sign of low magnesium levels, particularly in women who are perimenopausal or menopausal, is poor sleep, says McGregor. We all also lose magnesium through our sweat, so you might notice that your levels are lower in the warmer months compared with the colder ones.

If you suspect that you have a magnesium deficiency, it is important to consult a doctor who will be able to provide a proper diagnosis, including a blood test.

Which magnesium supplement is best?

If you are looking for a magnesium supplement to add in alongside your diet, it's important to consider the form of magnesium in the product. There are several different types:

• Magnesium citrate: This is a highly bioavailable form (which is just a fancy way of saying it's absorbed well by the body).
• Magnesium glycinate: Another highly bioavailable type, often good for people with sensitive stomachs.
• Magnesium sulfate: More commonly known as Epsom salts, this is usually added to hot baths or foot soaks to soothe aching muscles.
• Magnesium malate: Another version that's very good for sensitive stomachs.
• Magnesium chloride: Often found in skin care products (like BetterYou's body butter) or topical supplements.
• Magnesium oxide: Generally the least bioavailable form – this is more commonly used to treat digestive issues and heartburn.

While we might naturally turn to a magnesium supplement in pill form, McGregor says that for recreational athletes, she would tend to recommend a spray or a skin-absorbed supplement (such as body butters, oils or flakes) first and foremost. This is because magnesium is well-absorbed through the skin. A post-run magnesium bath is a great way to help soothe both muscles and mind too.

If you're opting for a pill or a capsule, magnesium citrate, glycinate or malate tend to work best.

When is it best to take magnesium supplements?

According to McGregor, it's usually better to take a magnesium supplement later in the day, particularly if you're using it to help with sleep. She also says to consider the other nutrients that you're taking it with – magnesium competes with calcium for uptake in the body, for example.

You also need to be careful not to take too much magnesium. McGregor recommends no more than 1g per day. The NHS warns that taking high doses of magnesium (more than 400mg) for a short time can cause diarrhoea, though there's not enough evidence to say what the effects might be of taking high doses of magnesium for a long time.