Magnesium is a mineral your body uses for muscle and nerve function, blood sugar control and blood pressure, as well as for making protein, bone and DNA, according to the US National Institutes of Health (NIH). The best sources are nuts, seeds, beans and other pulses, wholegrains and green leafy vegetables such as spinach.
Most people can get all the magnesium they need from a varied, balanced diet, the NHS says. This guide shows how much you need, which foods contain the most, and when a supplement might, or might not, make sense.
How much magnesium do you need?
Recommendations differ between countries:
- UK (NHS): 270 mg a day for women and 300 mg a day for men aged 19 to 64
- US (NIH Office of Dietary Supplements): 310 to 320 mg a day for women and 400 to 420 mg a day for men, depending on age, and 350 to 360 mg a day during pregnancy
Either way, the amounts are achievable through food. Check the advice where you live if you're unsure which applies to you.
Foods rich in magnesium
The NIH lists these as good sources. Servings are US measures: 1 oz is about 28 g, and a cup is about 240 ml.
Food Serving Magnesium Pumpkin seeds, roasted 1 oz 156 mg Chia seeds 1 oz 111 mg Almonds, dry roasted 1 oz 80 mg Spinach, boiled ½ cup 78 mg Cashews, dry roasted 1 oz 74 mg Peanuts, oil roasted ¼ cup 63 mg Shredded wheat cereal 2 large biscuits 61 mg Soya drink, plain 1 cup 61 mg Black beans, cooked ½ cup 60 mg Edamame beans, cooked ½ cup 50 mg Peanut butter, smooth 2 tbsp 49 mg Potato, baked with skin 3.5 oz (about 100 g) 43 mg Brown rice, cooked ½ cup 42 mg Plain low-fat yoghurt 8 oz (about 225 g) 42 mg Kidney beans, tinned ½ cup 35 mg Banana 1 medium 32 mg Wholemeal bread 1 slice 23 mg Avocado, cubed ½ cup 22 mg Refined grains can contain much less. For example, the NIH lists half a cup of cooked white rice at 10 mg, compared with 42 mg for brown rice.
Easy ways to eat more magnesium
- Sprinkle pumpkin seeds or chia seeds over porridge, yoghurt or salad.
- Have a small handful of unsalted almonds or cashews as a snack.
- Add black beans, kidney beans or chickpeas to soups, stews and curries.
- Swap white rice and white bread for brown rice and wholemeal bread.
- Stir spinach into pasta sauces, omelettes and curries.
- Choose a shredded wheat or other wholegrain cereal for breakfast.
- Keep the skin on baked potatoes.
For more ideas, see our guide to healthy food swaps.
Who may not get enough
According to the NIH, men over 70 and teenagers are the most likely to have low intakes. People with digestive conditions, type 2 diabetes or long-term alcohol dependence, and older people, are also more likely to be low in magnesium.
Signs of magnesium deficiency include loss of appetite, nausea, vomiting, tiredness and weakness. These symptoms are common and have many possible causes, so see a GP rather than assuming it's low magnesium.
Do you need a supplement?
Usually not. The NHS says you should be able to get all the magnesium you need from a varied and balanced diet. If you do take a supplement, the limits again differ by country:
- The NHS says taking 400 mg or less a day from supplements is unlikely to cause any harm, but that high doses of more than 400 mg for a short time can cause diarrhoea.
- The NIH sets an upper limit of 350 mg a day for adults from supplements and medicines (magnesium from food doesn't count). Too much can cause diarrhoea, nausea and stomach cramps, and extremely high intakes can lead to an irregular heartbeat and cardiac arrest.
Magnesium supplements can also interact with some medicines, according to the NIH:
- bisphosphonates, used for osteoporosis, may not be absorbed well if taken too close to products high in magnesium
- some antibiotics may not be absorbed if taken too close to a magnesium supplement
- some diuretics (water tablets) can raise or lower the amount of magnesium your body loses
- long-term use of some prescription medicines for acid reflux or stomach ulcers can lower magnesium levels
Talk to a GP or pharmacist before taking a magnesium supplement, especially if you take any regular medicines or are pregnant.
The bottom line
You don't need special products to get enough magnesium. A handful of nuts or seeds, beans a few times a week, wholegrains instead of refined versions, and plenty of leafy greens will cover most people's needs. If you're thinking about a supplement, check with a GP or pharmacist first, and don't go over the recommended limit.
Not medically reviewed. This article is general information, not personal medical advice.
Sources
- Vitamins and minerals: others (magnesium), NHS
- Magnesium: Fact Sheet for Health Professionals, NIH Office of Dietary Supplements
- Magnesium: Fact Sheet for Consumers, NIH Office of Dietary Supplements
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