If you train regularly and something feels slightly off, your sleep is patchy, your muscles cramp after hard sessions, or your energy flags earlier than it should, magnesium is one of the first minerals worth looking at. It's not glamorous, and it doesn't get the marketing attention that protein or creatine does. But few nutrients affect as many systems in your body at once.
This guide covers what magnesium actually does, how much you need, where to get it from food, and what to look for if you decide a supplement makes sense. Whether you're brand new to supplements or just want to stop guessing at the shelves, this is the overview you need.
What Magnesium Does in the Body
Magnesium is involved in more than 300 enzyme reactions in the body. That means the mineral has a hand in processes ranging from energy production and muscle contraction, to nerve signalling and DNA repair.
More specifically, magnesium plays a direct role in:
- Converting food into usable energy (ATP synthesis)
- Muscle contraction and relaxation, including the heart
- Nerve transmission and nervous system regulation
- Maintaining bone density alongside calcium and vitamin D
- Blood glucose regulation
For people who train hard, that muscle-contraction and energy-metabolism connection is relevant. When magnesium is low, those processes work less efficiently. You don't need clinical deficiency to feel the effects. Suboptimal intake is common and can affect how you train, recover, and sleep.
How Much Magnesium Do You Need?
The Nutrient Reference Values for Australia and New Zealand (NHMRC & Ministry of Health, 2006) set the Recommended Dietary Intake (RDI) for adults at:
- Men: 420mg per day
- Women: 320mg per day
- Pregnant women: 350–360mg per day
If you're supplementing, the upper level from supplements alone is 350mg per day. Above that, the main risk is gastrointestinal upset, and is the most common sign you've taken too much.
It's worth knowing that exercise may modestly increase magnesium needs. Physically active people tend to have higher magnesium losses, so if you train consistently, sitting at the lower end of intake may not be enough to cover your bases (Nielsen and Lukaski, 2006).
Magnesium from Food: What to Eat and How Much You're Actually Getting
Whole foods are the best starting point. Magnesium is found in good amounts across a range of plant foods. The Australian Bureau of Statistics' 2011-12 National Nutrition and Physical Activity Survey found that around one in three adult Australians didn't meet their daily requirement. New Zealand faces the same shortfall, magnesium ranks among the most under-consumed nutrients in both countries (Refer & Stoney, 2024). Processed, refined diets are the main culprit. When grains are milled and vegetables replaced with packaged food, magnesium intake drops.
High-magnesium foods include:
- Pumpkin seeds: ~150mg per 30g serving — one of the richest sources available
- Dark leafy greens (spinach, silverbeet): ~150mg per cup cooked
- Almonds and cashews: ~75–80mg per 30g
- Lentils: ~35mg per half-cup cooked
- Black Beans: ~60mg per half-cup cooked
- Whole grains (brown rice, oats): ~40–60mg per serve
- Dark chocolate (70%+): ~50mg per 30g
- Avocado: ~30mg per 100g
- Banana: ~30–35mg per medium fruit
One catch: cooking and boiling can reduce magnesium content in some vegetables. Steaming or eating raw generally retains more magnesium, though for dense leafy greens like spinach, cooking is worth it anyway, since a cup of cooked spinach contains far more magnesium than a cup of raw spinach, even accounting for any losses. Highly processed versions of otherwise good foods, instant oats vs. rolled oats, white rice vs. brown, contain far less magnesium than their whole counterparts.
Some packaged foods and drinks (certain breakfast cereals, protein bars, electrolyte drinks) are fortified with magnesium. These can contribute to daily intake, but they're rarely a reliable primary source. Check the label, as magnesium content varies widely and the form used matters for how much you actually absorb.
Types of Magnesium: Which Form Is Which
This is where most people get confused at the supplement shelf. "Magnesium" on a label tells you almost nothing useful on its own. What matters is the compound it's bonded to, because this affects how well it's absorbed, how it behaves in your gut, and what it's best suited for.
Magnesium supplements fall into two broad categories: organic forms (bonded to organic molecules like amino acids or acids) and inorganic forms (bonded to inorganic salts). The evidence generally favours organic forms for absorption, though the research is limited and studies are hard to compare directly. Much of the difference comes down to magnesium oxide specifically, which absorbs poorly. Solubility is the more useful concept: forms that dissolve readily in the gut tend to absorb better, and most organic forms happen to be more soluble.
Magnesium Glycinate (organic)
Magnesium bonded to the amino acid glycine. It's considered one of the best-absorbed forms available and is generally well-tolerated by people with sensitive stomachs. Glycine itself has calming properties, which is why glycinate is the form most associated with sleep support and stress relief. Good choice if: you want a daily supplement that's easy on digestion and you're using it primarily for sleep or recovery.
Learn more about magnesium glycinate in our blog Magnesium Glycinate: Benefits, Dosage and Why It's Worth Considering
Magnesium Citrate (organic)
Bonded to citric acid. Highly soluble and well-absorbed. The most common form in powdered supplements because it dissolves easily in water. At higher doses it can have a laxative effect. Good choice if: you want a powder format and your digestion handles it well. Back off the dose if you notice loose stools.
Magnesium Oxide (inorganic)
The cheapest and most common form in low-cost tablets. Unfortunately, it also appears to be the least well-absorbed. One human trial showed lower serum magnesium levels compared to organic forms at equivalent doses (Kappeler et al., 2017). Its main use is as a gentle laxative or antacid. Worth knowing: if a supplement seems unusually cheap, check the label, it may be magnesium oxide.
Magnesium Malate (organic)
Magnesium bonded to malic acid. Malic acid is involved in energy metabolism, but consuming malic acid doesn't appear to influence energy levels directly. That said, the form itself is well-absorbed and gentle on the gut, so it's still a solid option. Good choice if: you want a tolerable everyday form and citrate causes issues.
Magnesium L-Threonate (organic)
A newer form of magnesium that, based on limited animal trials, can cross the blood-brain barrier better than other forms (Slutsky et al., 2010). In humans, its been shown to improve certain cognitive abilities such as learning and memory, particularly in older populations (Zhang et al., 2022). In general, it's a new form with little, but promising research, so it's worth keeping an eye on or trying for yourself.
Check out Switch Nutrition MAG3 Magnesium L-Threonate Powder
Magnesium Taurate (organic)
Bonded to taurine. Sometimes used for cardiovascular and blood pressure support. Evidence here is largely limited to animal studies and a small number of human trials.
Magnesium Sulfate (inorganic)
Better known as Epsom salt you can use in a bath. It's unclear if magnesium is absorbed through the skin with this method, or how much, so it's less reliable than oral supplementation.
Forms of Magnesium Supplements: Tablets, Capsules, and Powders
Beyond the type of magnesium, you also need to decide on the delivery format. The form doesn't hugely affect absorption on its own (capsules vs tablets vs powder), what matters most is the type of magnesium inside. That said, format does affect convenience, dosing flexibility, and how quickly it works.
Tablets and Capsules
The most common format. Simple to take, easy to travel with, and precisely dosed. Capsules tend to break down slightly faster than compressed tablets. Both work well for most people. If you're going for glycinate or malate specifically for sleep, taking a capsule 30–60 minutes before bed is easy to build into a routine.
Powders
Usually magnesium citrate or a blended form. Dissolve in water and drink. They're effective, often cost-competitive, and easy to adjust the dose. Some people find powders more practical if they're already making a pre-sleep or post-workout drink. Taste varies significantly between products, so check reviews before committing to a large tub.
Fortified Foods and Drinks
Some protein bars and breakfast cereals contain added magnesium. Most electrolyte drinks contain magnesium because it is one of the key electrolytes the body needs. These can top up intake but are rarely reliable as a primary supplement source. The magnesium content per serving is often low, and the form used isn't always disclosed. Think of these as a bonus on top of diet and a dedicated supplement, not a replacement.
Who Might Actually Benefit from Supplementing
Even after focusing on whole foods first, there are genuine reasons why some people benefit from a dedicated magnesium supplement:
- High training volume: Sweat losses and higher metabolic turnover can push needs up. If you're training hard most days, diet alone may not keep pace.
- High-processed diet: If whole grains, legumes, and leafy greens aren't staples in your meals, hitting 320–420mg daily from food alone is genuinely difficult.
- Poor sleep or high stress: Magnesium, particularly glycinate, is associated with nervous system regulation. The evidence isn't conclusive, but the mechanism is plausible and the risk profile of supplementing is low.
- Older adults: Magnesium absorption tends to decline with age, making adequate intake harder to maintain from food alone.
- People on certain medications: Proton pump inhibitors, diuretics, and some antibiotics can reduce magnesium absorption over time. Talk to your GP if this applies to you.
What the evidence doesn't support
A few popular claims about magnesium are worth tempering. The idea that magnesium dramatically boosts athletic performance in people who are already well-nourished is not well-supported. This is because magnesium isn't a performance enhancer in the way creatine or caffeine are. Two 2017 reviews found no significant improvements in muscle strength or power across the general population, but benefits can be seen in those who were deficient, such as the elderly or people with poor diets (Wang et al., 2017; Zhang et al., 2017). The goal is avoiding a deficiency, not chasing a surplus to gain an edge.
How to Take Magnesium
A few practical notes:
- With food or without: Magnesium can be taken with or without food. If you experience nausea, take it with a meal.
- Timing: Evening is popular. Some people find it helps with relaxation and sleep. There's no evidence that morning use is less effective for general sufficiency, so take it when you'll actually remember to.
- Splitting doses: If you're taking 300mg or more per day from supplements, splitting into two doses can reduce the chance of digestive upset.
- Calcium interaction: Very high calcium intake at the same time as magnesium can reduce absorption of both. This is rarely a real-world issue, but worth knowing if you're taking large doses of both.
If you're unsure where to start, check out our magnesium collection. We stock a range of formats and forms so you can match the supplement to your actual situation.
Conclusion
Magnesium is one of the most widely undersupplied minerals in the NZ diet, and the gap between what most people eat and what their body needs is real. If your training, sleep, or energy recovery isn't quite where it should be, checking your intake is a reasonable first step. Focus on whole foods first. If you do supplement, choose a well-absorbed form (glycinate and citrate are the most studied), pick a format you'll actually use consistently, and keep the dose within safe limits.
Ready to cover your bases? Browse our magnesium supplement range — we stock quality options across all the major forms and formats, so you can find something that fits your routine.
Frequently Asked Questions
What is the best type of magnesium supplement?
Magnesium glycinate and magnesium citrate are the most reliably absorbed forms based on current evidence. Glycinate tends to be gentler on digestion and commonly used for sleep and stress support. Citrate is well-absorbed and suits powder formats well, but can cause cause GI distress at higher doses. Magnesium oxide is widely available but not as well absorbed as these other types.
How much magnesium should I take per day?
The NZ/Australian RDI is 420mg/day for adult men and 320mg/day for adult women. From supplements specifically, the upper level is 350mg/day. Most people eating a balanced diet are getting some magnesium from food, so a supplement dose of 150–300mg per day is a reasonable place to start. If you're unsure, speak to a GP or registered dietitian.
What foods are highest in magnesium?
Pumpkin seeds are one of the richest sources, providing around 150mg per 30g. Other high-magnesium foods include dark leafy greens (spinach, silverbeet), almonds, cashews, black beans, brown rice, and dark chocolate with 70% or more cocoa. Lentils also contribute, though at a lower level than beans, with closer to 35–40mg per half-cup cooked versus around 60mg for black beans. Whole, minimally processed foods consistently outperform their refined counterparts for magnesium content.
Does magnesium help with sleep?
This is a popular claim, and there's a plausible mechanism. Magnesium (particularly glycinate) has a role in nervous system regulation and may support relaxation. Some studies in older adults with low magnesium found improved sleep outcomes after supplementation. The evidence in healthy adults with adequate baseline levels is less clear. It's not a guarantee, but the risk profile of magnesium glycinate is low, making it a reasonable thing to try.
Can I get enough magnesium from food alone?
Yes, if your diet is built around whole foods: plenty of leafy greens, legumes, nuts, seeds, and whole grains. Many people eating typical Western diets don't hit the RDI consistently though. Australian survey data shows roughly one in three adults falls short, and a 2024 analysis identified magnesium as one of the most under-consumed nutrients across both Australia and New Zealand (Starck et al., 2024). If your diet is high in processed food or you're training hard, supplementing is a practical way to close the gap.
Is magnesium powder better than tablets?
Not inherently. The format matters less than the type of magnesium inside. Powders (usually citrate) are convenient for people already making a pre-bed or post-workout drink and allow flexible dosing, and because they're dissolved in water before you drink them, the magnesium is already in solution, which gives a modest absorption advantage over tablets that need to break down in the gut first. Tablets and capsules are easier to travel with and more precisely dosed. Choose the format you'll actually use consistently, with a form of magnesium that suits your digestion.
References
Kappeler, D., Heimbeck, I., Herpich, C., Naue, N., Höfler, J., Timmer, W., & Michalke, B. (2017). Higher bioavailability of magnesium citrate as compared to magnesium oxide shown by evaluation of urinary excretion and serum levels after single-dose administration in a randomised cross-over study. BMC Nutrition, 3(7). https://doi.org/10.1186/s40795-016-0121-3
National Health and Medical Research Council & Ministry of Health. (2006). Nutrient reference values for Australia and New Zealand including recommended dietary intakes. Commonwealth of Australia. https://www.nrv.gov.au/nutrients/magnesium
Nielsen, F. H., & Lukaski, H. C. (2006). Update on the relationship between magnesium and exercise. Magnesium Research, 19(3), 180–189. PMID: 17172008
Slutsky, I., Abumaria, N., Wu, L.-J., Huang, C., Zhang, L., Li, B., Zhao, X., Govindarajan, A., Zhao, M.-G., Bhaskaran, M., Bhaskaran, M., Tonegawa, S., & Liu, G. (2010). Enhancement of learning and memory by elevating brain magnesium. Neuron, 65(2), 165–177. https://doi.org/10.1016/j.neuron.2009.12.026
Starck, C. S., Cassettari, T., Beckett, E., Marshall, S., & Fayet-Moore, F. (2024). Priority nutrients to address malnutrition and diet-related diseases in Australia and New Zealand. Frontiers in Nutrition, 11, Article 1370550. https://doi.org/10.3389/fnut.2024.1370550
Wang, R., Chen, C., Liu, W., Zhou, T., Xun, P., He, K., & Chen, P. (2017). The effect of magnesium supplementation on muscle fitness: A meta-analysis and systematic review. Magnesium Research, 30(4), 120–132. https://doi.org/10.1684/mrh.2018.0430
Zhang, Y., Xun, P., Wang, R., Mao, L., & He, K. (2017). Can magnesium enhance exercise performance? Nutrients, 9(9), Article 946. https://doi.org/10.3390/nu9090946
Zhang, C., Hu, Q., Li, S., Dai, F., Qian, W., Hewlings, S., Yan, T., & Wang, Y. (2022). A Magtein®, magnesium L-threonate, -based formula improves brain cognitive functions in healthy Chinese adults. Nutrients, 14(24), Article 5235. https://doi.org/10.3390/nu14245235
