Quick answer: Magnesium supports normal muscle and nerve function, energy production, and restful sleep for some people. In NZ, most adults can meet needs through food, but supplements can help when intake is low. Choose a form you tolerate, start with a modest dose, and check interactions if you take regular medicines.
Magnesium is one of those nutrients that quietly does a lot of work. If you are dealing with leg cramps, restless sleep, stress, or you simply want to support healthy ageing, magnesium often comes up in the conversation. Here is a practical guide for New Zealanders, with a focus on what magnesium does, where to get it from food, and how to choose a supplement you can actually stick with.
What is magnesium?
Magnesium is an essential mineral your body uses for hundreds of processes, including energy production, muscle contraction and relaxation, and nerve signalling. It also supports normal heart rhythm and plays a role in bone structure. Because your body cannot make magnesium, you need a steady supply from food. Supplements can be helpful when intake is low, needs are higher, or your diet is limited.
Why people in NZ look at magnesium
Magnesium is not a cure-all, but adequate intake supports everyday functions that matter, especially as we get older. Most benefits are about supporting normal body function, and results from supplements can vary from person to person.
Muscle function, recovery, and cramps
Magnesium supports normal muscle function and helps with the balance between contraction and relaxation. If cramps are related to low intake, hydration, or training load, improving magnesium intake can be a sensible part of your plan. Cramps can have many causes (including medications, circulation, or nerve issues), so persistent or severe symptoms are worth discussing with a clinician.
Sleep, relaxation, and stress support
Some people find magnesium helpful for winding down at night, particularly when stress and tension are part of the picture. The effect is often subtle, so we suggest pairing magnesium with basics that move the needle: consistent sleep and wake times, morning light, and a pre-bed wind-down that does not involve scrolling.
Energy and day-to-day wellbeing
Magnesium plays a role in energy metabolism. If your diet has been low in whole foods, improving magnesium intake can support how you feel day to day. It is also a helpful 'foundations' nutrient to review if you are rebuilding routine after illness, appetite changes, or a busy season.
Digestion and bowel regularity
Some forms of magnesium draw water into the bowel, which can soften stools. This is why certain magnesium products are used for occasional constipation support. If loose stools are already a problem, you may prefer a gentler form and a lower dose.
Common reasons magnesium intake can be low
- Low variety diets: fewer whole grains, legumes, nuts, and leafy greens.
- Reduced appetite: common with ageing, illness, or medication changes.
- Higher needs: strenuous exercise, sweating, or periods of stress.
- Digestive issues: conditions that reduce absorption can affect mineral status.
If any of these feel familiar, magnesium is a reasonable nutrient to review alongside protein, fibre, and overall calorie intake.
Food sources of magnesium in a typical NZ diet
We like food-first foundations. Magnesium-rich options include:
- nuts and seeds (pumpkin seeds, almonds, sunflower seeds)
- legumes (lentils, beans, chickpeas)
- whole grains (oats, wholegrain bread, brown rice)
- leafy greens (spinach, silverbeet)
- avocado and bananas
- cocoa and dark chocolate (in reasonable portions)
Simple NZ-friendly ideas: add pumpkin seeds to yoghurt, swap white bread for wholegrain, build a lentil soup, or add a handful of spinach to eggs or pasta. If chewing is difficult, soups, smoothies, and soft-cooked legumes can be easier ways to add magnesium-rich foods.
Choosing a magnesium supplement in NZ
If you are considering a supplement, we recommend starting with two checks: (1) the form of magnesium and (2) the amount of elemental magnesium per serve.
If you want to browse options, start here: Magnesium collection. For an example of a combined relaxation and sleep focused option, see Super Magnesium 1000 (relaxation and sleep).
Elemental magnesium matters (how to read the label)
Supplement labels often list a compound, such as magnesium citrate or magnesium glycinate. What you want to find is the amount of elemental magnesium provided per tablet, capsule, or scoop. Two products can look similar on the front, but deliver very different elemental amounts.
- Check 'Nutrition Information' or 'Supplement Facts' for Magnesium (elemental).
- If the dose is listed as a compound only, look for a line that converts it to elemental magnesium.
- Be cautious comparing powders and tablets. Serving sizes differ and can change the total dose quickly.
Common magnesium forms and how they feel
- Magnesium glycinate: often chosen for evening use because it is typically gentle on digestion.
- Magnesium citrate: commonly used and absorbs well for many people, but higher doses may loosen stools.
- Magnesium oxide: higher elemental magnesium by weight, but can be more laxative for some.
- Magnesium malate: sometimes chosen for daytime use.
- Magnesium L-threonate: a newer form some people choose for cognitive-focused routines, although evidence and individual response vary.
If you are sensitive to stomach upset, we usually suggest starting with a gentler form and a lower dose, then adjusting based on tolerance.
Capsules, tablets, powders, and 'one-a-day'
There is no universally best format. Capsules and tablets are simple for most people, powders can be useful if swallowing pills is hard, and 'one-a-day' products can improve consistency. The best option is the one you can take consistently without side effects.
How much magnesium do you need?
Needs vary by age and life stage. As a practical rule of thumb, many adults aim for roughly 300 to 400 mg per day from food and supplements combined. Older adults may be more likely to fall short if diet variety is limited.
If you supplement, we suggest:
- start with a modest dose and increase gradually if needed
- split doses across the day if you get stomach upset
- use the elemental magnesium number on the label to compare products
- follow label directions unless a clinician has advised otherwise
When to take magnesium
Timing depends on your goal and tolerance. Here are common approaches we see work well:
- For sleep: take in the evening, 1 to 2 hours before bed.
- For cramps or general support: split morning and evening doses.
- For digestion support: a single evening dose may be enough, but start low to avoid rushing to the loo.
- If digestion is sensitive: take with food.
Consistency matters more than perfect timing. If you miss a day, do not double up, just return to your usual routine.
Magnesium safety, side effects, and interactions
The most common side effect is loose stools, especially with higher doses or certain forms. If that happens, reduce the dose, split it, or switch forms.
Who should check with a clinician first
- people with kidney disease (magnesium is cleared through the kidneys)
- people on multiple regular medicines, especially if doses are time-sensitive
- pregnant or breastfeeding people who are unsure about dosing
Medicine timing: a simple spacing rule
Magnesium can reduce absorption of some medicines (including certain antibiotics, thyroid medicine, and osteoporosis medicines). We recommend separating magnesium from these medicines by 2 to 4 hours and checking with your pharmacist or GP if you are unsure.
Magnesium for older adults (70+) in NZ
If you are in your 70s or beyond, magnesium can be a useful nutrient to review, but the best approach is usually simple and steady. We see the biggest wins when people combine magnesium with diet basics and a routine they can follow.
- Start lower: digestion can be more sensitive, so a smaller dose taken consistently is often better than a high dose that causes diarrhoea.
- Review medicines: it is common to have multiple prescriptions. Ask your pharmacist about spacing magnesium away from time-critical medicines.
- Hydration and fibre still matter: if you are using magnesium for bowel regularity, water intake and fibre are part of the same picture.
- Consider splitting doses: morning and evening can reduce stomach upset and may feel steadier.
If you have reduced kidney function or have been told to limit minerals, check with your GP before supplementing.
Which magnesium should you choose for your goal?
People respond differently, but these are common starting points we use as a guide:
| Goal | Often chosen | Practical tip |
|---|---|---|
| Sleep and relaxation | Glycinate (sometimes citrate) | Take 1 to 2 hours before bed and keep caffeine earlier in the day. |
| Muscle cramps | Citrate, glycinate, or malate | Try splitting doses and pair with hydration and gentle calf stretching. |
| Occasional constipation | Citrate (lower dose first) | Increase slowly and stop if stools become too loose. |
| General dietary top-up | Any well tolerated form | Focus on elemental magnesium per serve and consistency. |
Can you test magnesium levels?
Standard blood tests measure magnesium in the bloodstream, but most magnesium is stored in tissues and bone. That means a normal blood result does not always rule out low intake. If you suspect your diet has been low, a food-first upgrade plus a careful supplement trial can be a practical approach. For symptoms that persist or worsen, work with your GP to rule out other causes.
FAQs
What does magnesium do in the body?
Magnesium helps your body make energy and supports normal muscle and nerve function. It also plays a role in heart rhythm, bone health, and many enzyme reactions.
Which type of magnesium is best for sleep?
Many people prefer magnesium glycinate or magnesium citrate for evening use because they are often well tolerated. The best option is the one you can take consistently without stomach upset.
How much magnesium should I take?
Needs vary by age and life stage, and most adults aim for roughly 300 to 400 mg per day from food and supplements combined. If you supplement, we suggest starting low, checking the label for elemental magnesium, and adjusting based on tolerance and advice from a health professional.
How long does magnesium take to work?
Some people notice changes in a few days, while others need a few weeks of consistent use, especially if low intake was part of the problem. Track sleep, cramps, or digestion for 2 to 4 weeks and reassess.
Can magnesium cause diarrhoea?
Yes. Higher doses, especially of magnesium oxide or citrate, can loosen stools. Reducing the dose, splitting it across the day, or switching to a gentler form can help.
Is magnesium safe with common medicines?
Magnesium can interact with some medicines, including certain antibiotics, thyroid medicine, and osteoporosis medicines, by reducing absorption. We recommend separating doses by 2 to 4 hours and checking with your pharmacist or GP if you take regular prescriptions.
Next steps
- Shop magnesium supplements
- Explore sleep support options
- Support for muscles and mobility
- Sleep guidance and common causes
- Best magnesium supplement in NZ: what to look for
- Magnesium dosage: timing and practical starting points
- Magnesium price in NZ: typical ranges and value checks
