Magnesium: how much per day, when to take it and which side effects

Magnesium is the mineral that raises the most practical questions: how much per day, when to take it, and why it sometimes gives you stomach ache or diarrhoea. The answers are simpler than the range of jars suggests. Below they are set out, with the figures from the Netherlands Nutrition Centre and the claims approved in the EU.

How much magnesium per day?

For magnesium there is no recommended daily amount but an adequate intake. For men from 18 years that is 350 milligrams a day and for women 300 milligrams, also during pregnancy and breastfeeding. For children: 170 milligrams at age 1 to 2, 230 milligrams from 3 to 9, and from 10 to 17 years 300 milligrams for boys and 250 for girls. These are the figures of the Dutch Health Council, as published by the Netherlands Nutrition Centre.

If you take in slightly less, you do not have a deficiency straight away. For most people the adequate intake is more generous than what they need.

Where is magnesium found?

In wholegrain cereal products, vegetables, nuts, milk and dairy products and meat. Tap water contributes a little too. A few portions with their magnesium content:

• A handful of unsalted nuts (25 grams): 54 milligrams
• A tablespoon of cooked spinach (50 grams): 39 milligrams
• A tablespoon of cooked wholewheat pasta (60 grams): 28 milligrams
• A piece of cooked chicken breast (70 grams): 25 milligrams
• A slice of wholemeal bread (35 grams): 19 milligrams
• A glass of semi-skimmed milk (150 ml): 18 milligrams

Anyone who eats wholegrain, vegetables daily and the occasional handful of nuts gets a long way with food alone. A deficiency is therefore uncommon. It can arise if your kidneys or bowels work poorly.

What does magnesium do?

Magnesium is needed for the formation of bone and muscle, for the transmission of impulses in muscles and nerves and for the working of a large number of enzymes. These claims are approved in the EU:

• Magnesium contributes to a reduction of tiredness and fatigue
• Magnesium contributes to normal energy-yielding metabolism
• Magnesium contributes to normal functioning of the nervous system and normal muscle function
• Magnesium contributes to normal psychological function
• Magnesium contributes to the maintenance of normal bones and teeth
• Magnesium contributes to electrolyte balance and normal protein synthesis

What is not on the list: sleep. Magnesium is often searched for in combination with sleep, but there is no approved claim for that. The claim that comes closest is the one about normal functioning of the nervous system.

When do you take magnesium?

The time of day does not matter. Magnesium is not a fat-soluble vitamin, so it does not need a meal with fat, and it is not iron, so it does not need an empty stomach. Many people take it in the evening because it fits their routine. That is a habit, not a rule. If it upsets your stomach, take it with a meal.

Magnesium can be taken with vitamin D, B vitamins, vitamin C, zinc and omega 3. There is no known reason to separate it from those. Only calcium and iron you take apart, and that rule is about calcium and iron between themselves, not about magnesium. More on that in which vitamins can you take together.

Side effects of magnesium

The best-known side effect is diarrhoea, sometimes with stomach cramps. It is caused by magnesium that is not absorbed and draws water into the bowel. The Netherlands Nutrition Centre uses 250 milligrams a day as the tolerable upper level for magnesium from supplements, on top of what you get from food. Above that, bowel complaints can develop. For magnesium from food there is no upper level; the excess is simply passed in urine.

If one capsule already gives you complaints, take it with a meal or choose a lower dose. If you take medication for the kidneys, the heart or against stomach acid, or have kidney disease, consult your doctor or pharmacist first. With poor kidney function magnesium can accumulate.

How do you recognise a magnesium deficiency?

A deficiency is uncommon, because magnesium is in so many foods. Possible signals are general listlessness or tiredness and muscle cramps. In extreme cases heart rhythm disorders. The difficulty is that a doctor cannot measure a deficiency well: only 1 per cent of the magnesium in your body is in the blood, about half is in bones and teeth, the rest in cells, muscles and nerve tissue. A normal blood value therefore does not rule out a deficiency, and muscle cramp has other causes too. If you have persistent cramps or tiredness, see your GP and have magnesium, iron, vitamin B12 and vitamin D looked at together.

Which supplement fits?

The magnesium capsules by Together contain 198 milligrams of magnesium per capsule, 53 per cent of the reference intake, extracted from mineral-rich seawater. One capsule a day stays below the upper level of 250 milligrams for supplements. Vegan, in a plant-based capsule, packed in a resealable pouch.

If you are looking at magnesium because of tiredness, the combination with B vitamins makes sense: vitamins B2, B6, B12 and folic acid carry the same claim about tiredness and fatigue and come together in the B complex by Together. Which other nutrients belong there is in which vitamins and minerals play a role in energy.

A supplement does not replace a varied diet. If complaints persist, see your GP.

Frequently asked questions about magnesium