Natural Energy. Nothing Else. Magnesium is a good test of that idea: a plain mineral with strong authorised evidence behind it, and a long list of online claims that go well beyond the science. This guide separates the two: what magnesium does in your body, why so many people fall short, what the research says about sleep and training, the best food sources, and how to choose a supplement safely. For the wider picture, start with our Nutrition Hub.
Start with the target. UK adults are advised to get 300mg of magnesium a day for men and 270mg a day for women [5]. That sounds easy. For a lot of people, on a lot of days, it isn't.
What Is Magnesium?
Magnesium is an essential mineral. Your body can't make it, so it has to come from food and drink. An adult body holds around 25g of it in total. Roughly 50-60% sits in your bones, most of the rest is in muscle and other soft tissue, and less than 1% is found in the blood [6]. That last detail matters later, because it's one reason magnesium status is hard to measure.
When intake drops, your kidneys cut the amount lost in urine to hold on to what you have [6]. A tightly managed system. But management isn't the same as supply.
What Magnesium Does in Your Body
A Co-Factor in More Than 300 Enzyme Systems
Magnesium is a co-factor in more than 300 enzyme systems that regulate reactions across the body, from protein synthesis and blood glucose control to muscle and nerve function and blood pressure regulation [6]. It's also needed to make DNA, RNA and the antioxidant glutathione [6].
Energy: Magnesium and ATP
ATP is the molecule your cells use as energy currency, and it only works in a form bound to magnesium [7]. Magnesium is required for glycolysis and oxidative phosphorylation, the processes that turn the food you eat into usable energy [6]. That's why magnesium carries two authorised health claims directly about energy: it contributes to normal energy-yielding metabolism, and it contributes to the reduction of tiredness and fatigue [2, 4].
Be clear about what that means. Magnesium doesn't add energy the way a coffee seems to. It's part of the machinery that releases energy from food. Short of a part, that machinery runs less well. Fully supplied, more magnesium won't make it run faster.
Muscle and Nerve Function
Magnesium plays a role in moving calcium and potassium across cell membranes, which is central to nerve signalling, muscle contraction and a normal heart rhythm [6]. Authorised claims reflect this: magnesium contributes to normal muscle function, normal functioning of the nervous system and electrolyte balance [4].
Bones and Teeth
With over half your body's magnesium stored in bone, it's no surprise that it contributes to the structural development of the skeleton [6]. Magnesium contributes to the maintenance of normal bones and teeth [4].
Magnesium, Focus and Mood
Magnesium contributes to normal psychological function [2, 4]. That's the authorised wording, and it's worth taking at face value: magnesium is part of normal brain function, not a cognitive enhancer. In the brain, magnesium helps regulate NMDA receptors, which are involved in nerve signalling, learning and memory [7].
What about stress and anxiety? A 2017 systematic review found some suggestive evidence of benefit from magnesium supplements in people prone to anxiety, but the quality of the studies was poor and the authors called for better trials [10]. Interesting, not settled.
If your focus fades in the afternoon, magnesium is one factor among several, alongside sleep, hydration, blood sugar and B vitamins. Vitamin B6 also contributes to normal psychological function [4]. We cover the full list in What's Actually Causing Your Afternoon Brain Fog?
How Much Magnesium Do You Need?
The UK Reference Nutrient Intake (RNI) for adults is 300mg a day for men and 270mg a day for women [5]. It's set to cover the needs of almost everyone, so meeting it gives you a comfortable margin.
Food labels use a different figure: the Nutrient Reference Value (NRV) of 375mg, used to calculate "% NRV" [13]. It's a labelling benchmark, not a personal target. And only around 30-40% of the magnesium in your diet is typically absorbed [6].
Why So Many People Fall Short
What the UK Data Shows
An analysis of the UK National Diet and Nutrition Survey found that a meaningful proportion of British adults in mid-life have magnesium intakes below the Lower Reference Nutrient Intake [3], the level below which intake is likely to be inadequate for most people [5]. Ordinary adults, eating ordinary food.
Processed and Refined Diets
Magnesium is concentrated in the foods modern diets tend to squeeze out: wholegrains, beans and lentils, nuts, seeds and leafy greens [6]. When grains are refined into white flour, the magnesium-rich bran and germ are removed [6]. A day of white bread, processed snacks and not much veg can land well short, even with plenty of calories.
The Soil Question
An analysis of UK food composition tables comparing 1940 with 1991 found that the magnesium content of vegetables had fallen by around a quarter [1]. The reasons are debated: crop varieties, farming methods and analysis techniques have all changed, so read it as a signal rather than a precise measurement. It's one reason we care about how our oats are grown, and why regenerative farming, which focuses on soil health, is part of the TRIBE story. More on that in our guide to natural foods and their benefits.
Signs Your Magnesium Intake May Be Low
This is where a lot of online content goes wrong. The early signs of magnesium deficiency include loss of appetite, nausea, fatigue and weakness. As it becomes more severe, it can cause numbness, tingling, muscle cramps and contractions, and abnormal heart rhythms [6].
The problem: almost every one of those symptoms is non-specific. Fatigue and muscle cramps have dozens of possible causes, from poor sleep and dehydration to iron deficiency or thyroid problems. Self-treating risks missing something that needs attention.
Testing isn't simple either. Because less than 1% of the body's magnesium is in the blood, and the body works hard to keep blood levels stable, a normal blood test doesn't always reflect what's stored in your tissues [6]. If you have persistent tiredness, cramps or any of the symptoms above, see your GP.
True deficiency is uncommon in healthy people and more often linked to gastrointestinal conditions that affect absorption, type 2 diabetes, long-term heavy alcohol use, some medicines, and older age [6].
The Best Food Sources of Magnesium
Seeds and Nuts
Pumpkin seeds are among the richest sources of all. A small 30g handful provides roughly 150mg of magnesium, around half the RNI [6]. Chia seeds, almonds, cashews and peanuts are also good sources, with a handful of almonds providing around half as much as the same amount of pumpkin seeds [6].
Legumes and Wholegrains
Black beans, kidney beans, edamame and soya all contribute, as do wholegrains such as oats, brown rice and wholemeal bread [6]. Because magnesium tends to travel with fibre in these foods, eating more of them helps with both. If fibre is your other gap, our guide to dietary fibre covers how to close it.
Leafy Greens, Potatoes and More
Spinach and other leafy greens, potatoes with their skins on and bananas all add to the total [6]. Magnesium isn't hard to find. It's just easy to crowd out.
Closing the Gap, Day to Day
Food first, always. But real life has late lunches, long afternoons and breakfasts eaten one-handed. That's where what you snack on matters.
It's one of the reasons we built TRIBE Protein + Focus the way we did. Each 60g bar contains 56.25mg of magnesium, 15% of the NRV, as magnesium citrate, one of the better-absorbed forms. Against the UK RNI, that's roughly a fifth of a woman's daily target and just under a fifth of a man's [5]. Alongside it: eight B vitamins and 10g of plant protein. Magnesium contributes to normal energy-yielding metabolism, normal psychological function and the reduction of tiredness and fatigue, and vitamins B6 and B12 also contribute to the reduction of tiredness and fatigue [4]. No caffeine, so there's nothing to crash from, a choice we explain in Why No Caffeine Is the Better Choice for Sustained Energy. The Choc Brownie and Peanut Butter flavours also carry 7-8g of fibre per bar.
Breakfast is the other easy win. TRIBE Protein Superblend is a vegan all-in-one shake with 20g of plant protein per serving and a 13 vitamin and mineral blend that includes magnesium citrate. Blend it with oats, a banana and a spoonful of pumpkin seeds and your breakfast brings magnesium from several directions at once.
Magnesium for People Who Train
For the TRIBE who train, strenuous exercise increases the amount of magnesium lost through sweat and urine, which may modestly raise requirements in people training hard [8]. Magnesium contributes to normal muscle function and electrolyte balance [4], both of which get tested on a long run or a heavy session.
The honest part: research suggests that low magnesium status can impair exercise performance, and that correcting a shortfall helps. But there's no good evidence that taking extra magnesium improves performance in people whose intake is already adequate [8]. Meet your needs consistently. Don't megadose before a race.
In practice, build magnesium-rich foods into the meals around your training. A Protein + Focus bar an hour or so before a session, or straight after when a proper meal is a while away, adds magnesium and B vitamins with plant protein and no caffeine. After a longer session, a Protein Superblend shake gets 20g of plant protein in quickly, with magnesium citrate in the mix. For longer efforts, our Training Hub covers fuelling in more depth.
Magnesium and Sleep: What the Evidence Actually Says
Magnesium is heavily marketed as a sleep aid. The evidence is much thinner than the marketing.
A 2021 meta-analysis of magnesium supplements for insomnia in older adults found only a small number of trials. Pooled results hinted at people falling asleep slightly faster, but the authors judged the evidence to be of low quality [9]. Research in younger, healthy adults is even thinner.
It's plausible that people who are genuinely low might notice a difference when they correct it. But there's no strong evidence that taking magnesium will improve sleep for most people, and no authorised health claim for sleep. If sleep is a persistent problem, talk to your GP.
Food vs Supplements: Forms, Absorption and Safe Limits
Most people can meet their needs through diet. If you're considering a supplement, not all forms behave the same way.
The Different Forms of Magnesium
Absorption differs between forms. Those that dissolve well in liquid, such as magnesium citrate, lactate, aspartate and chloride, are absorbed more completely than less soluble forms such as magnesium oxide [6]. In one randomised, double-blind study, magnesium citrate was found to be more bioavailable than magnesium oxide [11].
- Magnesium citrate: well absorbed and widely used. It's the form in Protein + Focus and Protein Superblend.
- Magnesium glycinate: popular and often described as gentle on the stomach, though direct comparisons with other forms are limited.
- Magnesium oxide: contains a lot of magnesium by weight, which makes it common in cheaper tablets, but it's less well absorbed [6, 11]. It's also used as a laxative.
How Much Is Too Much?
Magnesium from food isn't a safety concern for healthy people, because the kidneys remove any excess in urine [6]. Supplements are different. The EU Scientific Committee on Food set a tolerable upper level of 250mg a day for adults for magnesium from supplements and magnesium added to foods and drinks, not counting what's naturally in food [12]. The limit is based on the laxative effect: above it, diarrhoea becomes more likely [12].
One Protein + Focus bar provides 56.25mg, well within that limit, but count it if you also take a magnesium tablet.
Who Should Speak to a Doctor First
Speak to your GP or pharmacist before taking a magnesium supplement if:
- You have kidney disease. Reduced kidney function means the body can't clear excess magnesium effectively, raising the risk of magnesium building up to harmful levels [6].
- You take certain medications. Magnesium can reduce the absorption of bisphosphonates (used for osteoporosis) and some antibiotics, including tetracyclines and quinolones, so timing matters. Some diuretics and long-term use of proton pump inhibitors can affect magnesium levels in the other direction [6].
- You're pregnant, breastfeeding or managing a long-term condition. Get advice that fits your situation before adding supplements.
The Bottom Line
Magnesium does real, well-established work. It's needed to release energy from food, and it contributes to normal muscle function, normal psychological function and the maintenance of normal bones [4, 6]. Plenty of people fall short [3], the symptoms are easy to mistake for something else, and the claims around sleep and stress are more hopeful than proven [9, 10]. The fix isn't complicated: more seeds, nuts, beans, wholegrains and greens, a smart snack when the day gets long, and a supplement only if you actually need one. Natural Energy. Nothing Else.
Every TRIBE product purchased donates 1p to the TRIBE Freedom Foundation - over £2.4 million raised to date.
Frequently Asked Questions
Q: How much magnesium do I need a day?
A: The UK Reference Nutrient Intake is 300mg a day for men and 270mg a day for women [5].
Q: Does magnesium give you energy?
A: Not in the way caffeine seems to. Magnesium is needed to turn food into usable energy, and it contributes to normal energy-yielding metabolism and the reduction of tiredness and fatigue [2, 4]. If you're already getting enough, more won't add extra energy.
Q: Does magnesium help you sleep?
A: The evidence is limited and mixed. A 2021 review of trials in older adults found low-quality evidence of a small effect on falling asleep [9]. There's no strong evidence it improves sleep for most people.
Q: What are the signs of low magnesium?
A: Early signs can include fatigue, weakness, loss of appetite and nausea, and more severe deficiency can cause muscle cramps, tingling and abnormal heart rhythms [6]. These symptoms have many other causes, so speak to your GP rather than self-diagnosing.
Q: Can you take too much magnesium?
A: Not from food, if you're healthy. From supplements and fortified foods, the tolerable upper level for adults is 250mg a day, above which diarrhoea becomes more likely [12]. People with kidney disease should speak to a doctor before supplementing [6].
Q: How much magnesium is in TRIBE Protein + Focus?
A: 56.25mg per bar, 15% of the NRV, as magnesium citrate, alongside eight B vitamins and 10g of plant protein. Protein Superblend also includes magnesium citrate in its 13 vitamin and mineral blend.
References: [1] Thomas D. A study on the mineral depletion of the foods available to us as a nation over the period 1940 to 1991. Nutrition and Health. 2003;17(2):85-115. [2] EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA). Scientific Opinion on the substantiation of health claims related to magnesium. EFSA Journal. 2010;8(10):1807. [3] Derbyshire E. Micronutrient Intakes of British Adults Across Mid-Life: A Secondary Analysis of the UK National Diet and Nutrition Survey. Frontiers in Nutrition. 2018;5:55. [4] Commission Regulation (EU) No 432/2012 establishing a list of permitted health claims made on foods (as retained in UK law). [5] Department of Health. Dietary Reference Values for Food Energy and Nutrients for the United Kingdom. Report on Health and Social Subjects 41. London: HMSO; 1991. [6] National Institutes of Health, Office of Dietary Supplements. Magnesium: Fact Sheet for Health Professionals. [7] de Baaij JHF, Hoenderop JGJ, Bindels RJM. Magnesium in man: implications for health and disease. Physiological Reviews. 2015;95(1):1-46. [8] Nielsen FH, Lukaski HC. Update on the relationship between magnesium and exercise. Magnesium Research. 2006;19(3):180-189. [9] Mah J, Pitre T. Oral magnesium supplementation for insomnia in older adults: a Systematic Review & Meta-Analysis. BMC Complementary Medicine and Therapies. 2021;21(1):125. [10] Boyle NB, Lawton C, Dye L. The Effects of Magnesium Supplementation on Subjective Anxiety and Stress - A Systematic Review. Nutrients. 2017;9(5):429. [11] Walker AF, Marakis G, Christie S, Byng M. Mg citrate found more bioavailable than other Mg preparations in a randomised, double-blind study. Magnesium Research. 2003;16(3):183-191. [12] Scientific Committee on Food / EFSA. Tolerable Upper Intake Levels for Vitamins and Minerals. European Food Safety Authority; 2006. [13] Regulation (EU) No 1169/2011 on the provision of food information to consumers, Annex XIII (as retained in UK law).
