Magnesium

Magnesium is a mineral that helps the body to make energy from food and to maintain muscle and bone health. 1 Foods containing fibre generally contain magnesium.

The most common cause of magnesium deficiency is not getting enough from your diet. 2 Magnesium deficiency does not normally cause symptoms unless it’s been present for a long time. Low dose magnesium supplements are unlikely to cause harm. 1

Magnesium belongs to the important micronutrients and is the fourth most abundant mineral in the body and we need it to stay healthy. 2 Magnesium helps the body make proteins and energy. 2 It plays an important role in maintaining nerve and muscle function, normal heart rhythm, and blood pressure. 2

Magnesium helps with normal function of the parathyroid glands, which produce hormones needed for bone health. 1

Higher magnesium intake is associated with lower risks of stroke, diabetes, and cardiovascular disease. 3 Blood magnesium is lower in people who experience migraine headaches compared to those who don’t. Magnesium supplements may have a role in migraine prevention and might increase bone density in postmenopausal women. 2 3

The main causes of magnesium deficiency are low dietary intake, low absorption in the gut, or increased magnesium loss from the kidneys. Vitamin D deficiency decreases gut magnesium absorption and is more common in less sunny countries far from the equator. 4

Find out more about how vitamin deficiency tests work.

Over recent decades, magnesium intake in the standard western diet has reduced. Nearly two-thirds of people living in North America and Europe don’t get the recommended daily amount of magnesium. 4

The required daily amount of magnesium differs for men and women, and can be affected by age, pregnancy, and breastfeeding: 3

• Infants (birth to 12 months): 30-75mg/day
• Children/adolescents (1 to 18 years): 80-410 mg/day
• Adult females (>18 years): 310-320 mg/day, increased to 350-360 mg/day during pregnancy and lactation
• Adult males (>18 years): 400-420 mg/dayTaking up to 400mg a day of magnesium supplements is unlikely to cause harm. 1

You might need to supplement magnesium if you don’t get enough from your diet. However, magnesium supplements may be less effective if your magnesium deficiency is due to low absorption in the gut or an underlying health condition.

Some prescription medicines may also affect magnesium absorption. 4 It’s important to talk to your doctor if you think you might have a magnesium deficiency.

Magnesium supplements are available in different forms including:

• magnesium oxide
• magnesium citrate
• magnesium chloride
• magnesium glycinate
• magnesium sulfate.

Small studies show that magnesium citrate and magnesium chloride are better absorbed by the gut than magnesium oxide and magnesium sulphate.

High doses of magnesium supplements (more than 400mg daily) can cause diarrhea and cramping. 1 Magnesium chloride and magnesium oxide are most reported to cause these side effects. 3

Whole grains (e.g. brown rice, wholemeal bread), leafy green vegetables, nuts, legumes, and white potatoes are high magnesium foods. 1 2

Generally, foods that are high in fibre contain magnesium. 3

• Pumpkin seeds, roasted, 1 oz (156 mg per serving)
• Chia seeds, 1 ounce (111 mg per serving)
• Spinach, boiled, 1⁄2 cup (78 mg per serving)
• Potato, baked with skin, 3.5 oz (43 mg per serving)
• Peanut butter, smooth, 2 tbsp (49 mg per serving)
• Rice, brown, cooked, 1⁄2 cup (42 mg per serving)

If you think you might have a magnesium deficiency, a magnesium test which measures the amount of magnesium in the blood might be necessary. Magnesium deficiency doesn’t usually cause symptoms unless it has been present for a long time, so a magnesium test may help identify a magnesium deficiency before you develop symptoms.

Symptoms of a magnesium deficiency include: 3 5

• nausea
• irregular heartbeat
• muscle weakness
• muscle cramps
• tremor
• loss of sensation
• seizures
• drowsiness
• confusion

If you experience these symptoms, you should see a doctor.

Q: What is magnesium used for?

The body needs magnesium to make energy from food, to preserve bone health, as well as normal nerve and muscle function and heart rhythm.

Q: When to take magnesium?

It’s important to seek medical advice and assessment if you think you might have a magnesium deficiency. If you think you have a dietary magnesium deficiency, magnesium supplements can help you to increase your magnesium intake. It’s advised that you visit your doctor before starting any supplemental magnesium.

Q: When to see a doctor?

You should see a doctor if you develop tremors, loss of sensation, muscle weakness, seizures, drowsiness, or confusion. These can be symptoms of magnesium deficiency. Magnesium deficiency usually needs to be present for a long time for these symptoms to develop.

Q: What side effects can magnesium cause?

Taking 400mg of magnesium supplements or less daily is unlikely to cause harm. High doses of magnesium supplements (more than 400mg) can cause diarrhoea. Currently, there is not enough evidence about the long-term side effects of high doses of magnesium supplements over 400mg daily.