Magnesium: Food Sources and How to Boost Its Absorption
Articles
Magnesium is one of the most abundant minerals in the human body. When we look at basil, avocado, spinach or tree leaves, we see them green precisely thanks to magnesium, which is the central element of chlorophyll. Even though it is a vital mineral, it is the most commonly deficient nutrient after vitamin D. What functions does it perform in the body, which foods contain it, how should you supplement it properly, and is it even necessary?
What will you learn in this article?
- Why are we deficient in magnesium?
- What functions does magnesium perform in the body?
- Where is magnesium found?
- Magnesium in foods
- Who should take magnesium supplements?
- How do I know I need more magnesium?
- How much magnesium should I get per day?
- Which forms are well absorbed?
- Key takeaways
Why are we deficient in magnesium?
Even though this mineral is irreplaceable for the human body and plays so many important functions, most people suffer from a chronic deficiency. The World Health Organization (WHO) states that up to 75% of the US population is deficient and does not meet the daily intake of 420 mg. As for the Czech Republic, according to national monitoring carried out by the Centre for Health, Nutrition and Food (CZVP CZU), practically all age groups of the population fail to reach the recommended daily intake through their natural diet, because our body cannot produce this mineral on its own.
The main causes of magnesium deficiency in the population include:
Soil depletion and food processing: The magnesium content of fruit and vegetables has dropped over the last fifty years, and up to 80% of this mineral is lost during industrial food processing.
Poor eating habits: Mineral-poor soils, a diet rich in ultra-processed foods, artificial additives and excess sugar actively drain magnesium from the body’s stores.
Lifestyle and stress: Consuming alcohol and caffeine, and taking diuretics or certain medications, increase magnesium excretion. Physical exertion also has a significant effect (magnesium needs rise by 10 to 20% during exercise), and chronic stress in particular.
What functions does magnesium perform in the body?
Magnesium is an essential mineral involved in hundreds of biochemical processes. An adult body contains roughly 20 to 30 g of magnesium, the vast majority of it not free in the blood but inside cells, in bones and in muscles. That is also why a deficiency can be hard to detect.
Building bones and teeth
The majority, about 60% of the body’s magnesium, is found in the bones, where it serves as a ready reserve and contributes to the proper mineralisation of bones and teeth. Here it occurs mainly in a complex with calcium and phosphorus. A long-term magnesium deficiency can therefore contribute to excessive loss of bone density.
Activating enzymes and energy metabolism
Most magnesium is located inside cells, where it influences a wide range of enzymatic reactions. It is scientifically documented that it is involved in at least 300 reactions in the human body. It acts as an activator of many enzymes, especially those involved in energy metabolism, as magnesium helps convert all three basic nutrients (proteins, fats and carbohydrates). It is also required for the replication of DNA, its transcription into RNA and translation into protein, and for cell division.
Nerve-muscle balance: the “relaxation mineral”
An important function of magnesium is the regulation of nerve and muscle activity. By keeping calcium out of the cells (acting as a natural calcium blocker), it reduces neuromuscular excitability and helps protect the nervous system from “over-firing”. This also shows up outwardly: one of the signs of magnesium deficiency is a calf cramp, “tingling” in the limbs or an eyelid twitch.
Magnesium thus contributes to the normal functioning of the nervous system, normal muscle function and normal psychological function, and it also helps reduce tiredness and fatigue. By replenishing magnesium, we restore the body’s physiological balance and support its ability to calm down.
Muscle function including the heart
About 40% of the body’s magnesium is found in the muscles (mainly skeletal and heart muscle), where it is involved in the mechanism of muscle contraction and relaxation. As the heart is a muscle, magnesium contributes to its normal function and to maintaining electrolyte balance. Its role in cardiovascular health remains an area of active research.
Where is magnesium found?
In nature, magnesium is found mainly in the plant kingdom, where it plays a key role in photosynthesis. It is bound to chlorophyll, so any dark green vegetable is an excellent source, as are seaweeds. Plants also store their most important nutrients in the parts intended for reproduction and survival, that is, in seeds, nuts, and the skin and flesh of fruits. To a lesser extent, magnesium is also present in animal products such as meat, fish, dairy and eggs. It can also be found in quality drinking and mineral water.
When getting magnesium from food, however, keep in mind that the body cannot use the full amount it contains. Magnesium absorption from food can be hindered by so-called antinutrients:
Phytates and oxalates found in some grains and legumes
High fibre intake and phosphate additives (for example in fizzy drinks)
Excess calcium or zinc, which compete with magnesium for the same absorption pathways in the digestive tract.
Magnesium in foods
If you want to increase your magnesium intake naturally, focus on regularly including the following food groups in your diet:
Dark leafy greens and algae: Spinach, chard, parsley, broccoli, chlorella and spirulina are among the richest natural sources thanks to their high chlorophyll content.
Seeds and nuts: Pumpkin, sunflower, flax and chia seeds, as well as almonds, cashews, Brazil nuts and hazelnuts, contain high concentrations of magnesium.
Legumes and pseudocereals: Black and red beans, lentils, peas, tofu, quinoa, buckwheat and oats provide a steady dose of magnesium along with quality fibre.
Fruit: Bananas, avocados, raspberries, blackberries and dried fruit (dates, figs, apricots) are great sources.
Cacao beans and dark chocolate: Quality raw cacao and dark chocolate with a high cocoa content (70% or more) are a very rich source of this mineral.
Animal sources and mineral waters: You can get smaller amounts of magnesium from quality meat, fish (e.g. salmon or mackerel), eggs and magnesium-rich mineral waters.
Who should take magnesium supplements?
Essentially anyone who faces the everyday demands of modern life. If you are going through a mentally challenging period, exercise regularly or are preparing for exams, in short, the more demanding your situation, the more your body depletes its magnesium stores and the more you need to replenish them. Supplementation is also certainly appropriate if your diet is not balanced and does not include enough foods that are natural sources of magnesium.
Especially for parents: if you are considering supplementation for the little ones, read our article Magnesium for children: why it matters, how to spot a deficiency and which forms are suitable.
How do I know I need more magnesium?
The first signs of deficiency or imbalance that you may notice can be occasional muscle cramps, fatigue, loss of appetite or the classic eyelid twitch. More pronounced signs can include very frequent tingling in the limbs, frequent cramps, constipation, insomnia, restless and poor-quality sleep, and an overall state of discomfort and restlessness. Magnesium simply plays a role in so many important functions that its long-term deficiency can have a whole range of acute and chronic consequences. Measuring magnesium in the blood does not tell us much about the magnesium inside our cells, which is why a deficiency can be difficult to diagnose.
How much magnesium should I get per day?
The recommended daily intake varies from person to person and depends heavily on sex, age, physical activity and many other factors. In general, it is set at 320 mg for women and 420 mg for men per day. Higher needs apply, of course, to athletes, during long-term and chronic stress, with excessive intake of carbohydrates and sweets, industrially processed foods and alcohol, or if you have an absorption disorder.
Magnesium has a high safety profile and low toxicity, as the body efficiently excretes any excess through the kidneys into the urine. Because sudden high doses can cause nausea or other gastrointestinal discomfort (including diarrhoea), it is recommended to start gradually and not exceed the recommended daily dose.
Which forms are well absorbed?
When choosing magnesium, its chemical form plays a key role, as it fundamentally affects bioavailability. The most suitable are considered to be highly absorbable chelated and organic compounds: magnesium bisglycinate, malate (bound to malic acid, ideal for supporting energy metabolism) and taurate.
Magnesium citrate appears less suitable: although it shows higher absorption, in more sensitive individuals or at higher doses it easily causes a laxative effect. For this reason, this form may be suitable for people suffering from constipation.
At the very end of the spectrum is magnesium oxide, the least suitable option; this inorganic form has extremely low bioavailability (approximately 4%) and acts more as an osmotic laxative than as an effective source of magnesium the body can use systemically.
You will find a detailed overview of all forms and their differences in the article Types of magnesium: which is the best and how do they differ. When choosing a magnesium supplement, however, it is important to pay attention not only to its form but also to the quality of the raw material and possible heavy metal content. We cover this topic in detail in the article Magnesium and heavy metals contamination.
Key takeaways
Most of the population suffers from chronic deficiency: Although magnesium is vital, it is the most commonly deficient micronutrient after vitamin D. According to the WHO, up to 75% of people do not meet the recommended daily intake, due to depleted soils and industrial food processing.
Magnesium performs dozens of key functions in the body: It is involved in at least 300 enzymatic reactions, in energy metabolism, in building bones and teeth, and in the normal functioning of nerves and muscles. The body holds about 20 to 30 g, roughly 60% in the bones and 40% in the muscles.
Magnesium needs rise with stress and activity: The body’s magnesium stores are depleted quickly by mental and physical stress and by consuming alcohol, caffeine, sugar and ultra-processed foods. During exercise, the need for magnesium rises by up to 20%.
Deficiency shows up as fatigue and cramps: The first warning signs include muscle cramps, eyelid twitches, exhaustion, poor sleep and constipation. Standard blood tests may not reveal a deficiency inside the cells at all.
Stick to the recommended daily amounts: The general recommendation is 320 mg per day for women and 420 mg for men. Higher doses are not toxic (the body excretes the excess in urine), but a large one-off excess can cause digestive discomfort.
The right form and quality matter: Avoid poorly absorbed oxide form. To replenish magnesium in the body, choose highly bioavailable chelated forms (e.g. magnesium glycinate, malate or taurate) and check the purity of the raw material.
Sources:
DiNicolantonio, J. J., O'Keefe, J. H., & Wilson, W. (2018). Subclinical magnesium deficiency: a principal driver of cardiovascular disease and a public health crisis. https://openheart.bmj.com/content/5/1/e000668
Nielsen, F. H., & Lukaski, H. C. (2006). Update on the relationship between magnesium and exercise. https://journals.physiology.org/doi/full/10.1152/
Costello, R. B., et al. (2016). Perspective: Characterizing Medicine-Based and Public Health Implications of Magnesium. https://www.sciencedirect.com/science/article/pii/
Walker, A. F., et al. (2003). Mg citrate found more bioavailable than other Mg preparations in a randomised, double-blind study. https://www.jle.com/fr/revues/mrh/e-docs/mg_citrate_found_more_bioavailable_than_other_mg_preparations_in_a_randomised_doubleblind_study__260858/article.phtml
