What is magnesium?

Magnesium is an essential mineral present in many foods. It has an impressively diverse array of roles in human biology. Magnesium is not distributed evenly between organs though. Of the total amount of magnesium in your body (roughly 24 g, but this amount will be higher if you have big muscles and bones), approximately 50 to 60% is stored in your bones, 25 to 30% is in your muscles, and the remainder is in other soft tissues and blood. 

Within tissues, magnesium acts a cofactor for more than 300 enzymes and is required for energy (ATP) production. In fact, each molecule of ATP binds magnesium to form its most functional form, a magnesium-ATP complex, which carries most ATP in cells. Magnesium is also a key player in DNA and protein synthesis, cell membrane stability, nerve conduction, the synthesis and activation of vitamin D, bone health, cardiovascular regulation, and more… 

… it’s kind of a big deal. 

And while you could make a similarly long list for other essential nutrients, a key difference is that magnesium is the most common mineral deficiency, and magnesium concentrations in many of the foods we eat are actually dwindling over time as soil magnesium concentrations wane. 

Effects of magnesium on lifespan and healthspan 

It’s not possible to do lifespan experiments on people, but we can look to research on the general population to see if there’s any evidence of a relationship between magnesium intake or status and how long people live. There have been many such studies analyzing people in various parts of the world — enough that researchers have combined the results from all the studies to try to get a sense of what the literature at large shows. An analysis of this sort was published in 2021. It included 19 studies totalling over 1.1 million participants, and after participants’ magnesium intakes were estimated, participants were followed for 3.5 to 32 years in the different studies. The analysis showed that, overall, higher magnesium intake from foods and drinks was associated with a lower risk of dying from all causes combined as well as from cancer, specifically. Statistically, the sizes of these two effects were “large”, so there’s probably something to them. Furthermore, the data revealed that each 100 mg dietary magnesium increment per day was associated with a 6% reduced risk of dying from all causes combined and a 5% reduced risk of dying from cancer. 

Magnesium is an essential nutrient. These are needed for normal function of your body and either cannot be made your body or cannot be made in sufficient amounts to support good health. We therefore need them from the diet. There are reasons to think that insufficient intakes of essential nutrients will compromise lifespan, as put forward by Bruce Ames in his “Triage Theory”. The crux of this theory is that an insufficient intake of an essential nutrient will ration what there is of it to proteins needed for short-term survival and reproduction at the expense of proteins with larger roles in mitigating risk of chronic diseases and premature mortality. If this theory proves to be correct, magnesium supplementation might be particularly helpful given that most of us don’t consume enough of it.

Suffice it to say that all sorts of things go wrong during magnesium deficiency. In fact, magnesium’s roles are so broad that symptoms of deficiency are remarkably non-specific. Early signs include fatigue, weakness, nausea, and vomiting. As deficiency continues, a slew of other changes ensues, including numbness, muscle cramps, seizures, abnormal heart rhythms, and low serum levels of calcium or potassium. 

Positive effects of magnesium on human health

When overviewing the positive effects of magnesium intake on human health, it’s hard to know where to start! To narrow our scope, let’s focus on studies of magnesium supplementation. Since the effects of magnesium intake are so wide-ranging, we’ll bypass many use cases and won’t go deep into the details of how magnesium exerts its positive effects. 

Magnesium is key to cardiovascular health

Magnesium supplementation has various positive effects on cardiovascular health, one of which is reducing blood pressure. Systematic reviews of randomized controlled trials have found that supplementation tends to reduce blood pressure both while the heart is contracting and between contractions (i.e., both systolic and diastolic blood pressure) in several populations, including adults with normal blood pressure, adults with high blood pressure, adults with prediabetes, and adults with type-two diabetes. Magnesium has this effect by enhancing the ability of the cells (endothelia) that line blood vessel walls to relax in response to increased blood flow, although this effect is most evident in older people, less healthy people, and when magnesium is used in the long term. It’s also likely that magnesium positively affects certain blood lipids in some populations when dosed appropriately. In type-two diabetes, for example, magnesium can lower LDL cholesterol and/or raise HDL cholesterol. However, the data on blood lipids are inconsistent enough that we’re not confident any effects are meaningful.

Magnesium supports healthy insulin action and blood sugar control

There have been many studies of the effects of magnesium supplementation on people with blood sugar dysregulation. In type-two diabetes, for example, supplementation consistently reduces glycated hemoglobin (“HbA1c”), a proxy of average blood sugar levels over the previous 115 days or so. Magnesium may also improve blood sugar control following the kind of bolus of glucose that can be used to diagnose diabetes. Furthermore, in gestational diabetes, magnesium supplementation tends to lower fasting blood sugar and improve sensitivity to the hormone insulin, a key player in the storage of energy substrates, including glucose. It’s not entirely clear how magnesium has these effects, but mechanisms likely include changes in activity of insulin receptors, changes in a key transporter (“GLUT4”) that shuttles glucose into skeletal muscle and fat cells, and reductions in the formation of new glucose (“gluconeogenesis”) by the liver.

Magnesium boosts brain health, supporting mood regulation and sleep

Magnesium supplementation can slightly reduce feelings of stress and anxiety and lift mood in stressed people and individuals with mild anxiety and depression symptoms, respectively. For example, in 264 healthy stressed subjects with low blood magnesium levels, supplementation with 300 mg daily for 8 weeks reduced stress scores and improved measures of depression and anxiety. Similar findings have been reported in some other patient populations, such as fibromyalgia. The finding of a modest positive effect of magnesium supplementation on depression has been found repeatedly.

It's plausible that some of magnesium’s mood-lifting and stress-buffering actions relate to improved sleep. A systematic review of magnesium supplementation by older adults with insomnia found that magnesium speeds sleep onset by 17 minutes, on average, although this was based on only three studies. Furthermore, magnesium can be helpful in treating restless legs syndrome, a sleep disorder characterised by a strong urge to move the legs that comes on before sleep, impeding sleep. 

How magnesium affects brain function is up for debate, but since it’s involved in potassium and calcium transport across cell membranes, it's important for nerve transmission. By interacting with a calcium channel in some excitatory neuron receptors (NMDA), magnesium may also help protect neurons against excessive activation, which can lead to cellular damage. Regarding control of sleep and wakefulness, magnesium is one of several ions in the brain that help regulate sleep and wakefulness, respectively. The concentration of magnesium outside cells is generally low during wakefulness and high during sleep, and it’s plausible that magnesium supplementation might aid sleep by ensuring adequate magnesium availability for this regulation.

Magnesium can boost exercise performance and muscle recovery and is needed for bone health

In most people, about a quarter of bodily magnesium is stored in skeletal muscle, where magnesium has roles in many processes. A recent systematic review of magnesium supplementation found that magnesium improves muscle recovery and reduces muscle soreness following damaging exercise. This has been found whether the exercise is resistance training, running downhill, competitive cycling, or playing basketball. Interestingly, muscle damage is known to acutely worsen blood sugar control, and the study of running found that magnesium supplementation attenuated this effect. Again, it’s not clear how magnesium protects skeletal muscle, but it might have something to do with how muscles handle calcium, which is key to recruiting muscles to produce force.

Regarding bone, over half bodily magnesium is stored in bones and teeth. People who consume more magnesium tend to have more dense bones. Whether isolated magnesium supplementation improves bone health is not very clear, but this might be the case in certain groups of people. For example, magnesium supplementation has been found to reduce rates of bone turnover in postmenopausal women, as has sometimes been found in other groups of people, including healthy young men. Magnesium probably exerts positive effects on bone both directly (affecting cells involved in bone formation and breakdown) and indirectly (for example, through interactions with vitamin D). 

Our use of magnesium

Regarding dose, Coastline contains 150 mg elemental magnesium. Unlike the other ingredients in Coastline, this dose isn’t based on any one clinical trial. Looking across studies, magnesium supplementation dose-dependently increases magnesium status, and the effects accumulate over time with regular use. The dose we use is therefore our best guess at the dose most health-conscious people (Coastline users are generally quite a healthy bunch) would benefit from on a daily basis to bridge the gap between their dietary magnesium intakes and what we think is likely optimal for them. 

Regarding timing, magnesium is in the morning step of Coastline. One reason for this is that the morning step also contains inulin, which can enhance magnesium absorption. Honestly, we don’t think that the timing of magnesium intake matters hugely in most cases — some studies showing positive effects have people take it in the morning, some in the evening, some whenever. 

Regarding form, Coastline contains magnesium citrate, the second-best-studied form of magnesium after magnesium oxide. Magnesium oxide might be the most widely studied form, but it is less bioavailable than citrate, probably in part because it’s less soluble in water. As a result, magnesium oxide can be hard on the digestive system, producing laxative effects. 

There’s a HUGE amount of noise online about the myriad forms of magnesium available — glycinate, threonate, taurate, acetyltaurinate, malate, lactate, orotate, sulfate, chloride, and the list goes on! When we need some light entertainment at Coastline, we enjoy reading and listening to the claims people make about some of these, particularly the scientist-influencers and physician-influencers who make assertions that can be refuted by even a quick scan of research databases. The reality is that most forms of magnesium have simply not been rigorously compared head to head for their effects on different bodily systems, so much of this has not been substantiated. Another reality is that many of the in-vogue forms (threonate, ahem) barely have any clinical trials on their effects. And yet some of the least-proven forms are among the most expensive. The good news is that magnesium citrate has good bioavailability, there are reams of research showing positive effects of magnesium citrate on numerous human health outcomes, and magnesium citrate is cost effective. Despite the noise, our choice was quite easy.

Magnesium typical dietary intakes, reference intakes, and safety

Magnesium is in the centre of chlorophyl molecules, so many plants are relatively rich sources of magnesium, including seeds, nuts, green vegetables (spinach, broccoli, etc), beans, grains, soybeans, potatoes, bananas, and cocoa. However, few foods are very rich in magnesium, and most people consume less magnesium than they need for optimal health. 

The Recommended Dietary Allowance (RDA) for an essential nutrient is the amount predicted to meet the needs of 97 to 98% of the population. The RDA was set in 1999 at 310 mg per day for women past the age of 30 and 420 mg per day for men of the same age. In turn, the European Food Safety Authority set the Adequate Intake (AI) to 350 mg per day for men and 300 mg per day for women. Recommended values for women are 30 to 40 mg higher during pregnancy, but not different during lactation. 

 “Western” diets tend to be low in magnesium-rich foods, and it’s been estimated that the majority of adults fail to meet their magnesium needs. For example, an analysis of trends in magnesium intakes in the US from 2003 to 2018 reported that about 50% of 19- to 30-year-old adults fail to meet the Estimated Average Requirement, with average intakes of around 300 mg per day. Intakes are lower still among older adults, averaging 276 mg per day in people over age 70. 

It’s difficult to accurately estimate magnesium intakes using dietary recall methods, so an alternative method is to use biomarkers of magnesium intakes. The gold standard is arguably a magnesium loading test to determine magnesium retention, but measuring levels in blood serum is much easier and hence more common. One of the problems with this method is that only about 0.3% of bodily magnesium is in the serum though! Irrespective of how status has been tested though, scientists have documented that people with various chronic health conditions have lower magnesium status than healthier people.

Reference intakes such as the RDA and AI create contention, and smart people have argued persuasively that the dietary requirements are too low (see this, for instance). Importantly, magnesium needs do vary quite a lot, and because of this we think that reference intakes can mislead people. For example, those of us who carry lots of muscle and bone and people who exercise a lot will need more magnesium than their smaller, more sedentary counterparts. This is one reason why some people think that magnesium recommendations should be scaled to bodyweight. Various medications can also tax magnesium status, including some diuretics, gastroesophageal medications, immunosuppressants, cancer medications, and many more.

Magnesium supplementation is perfectly safe. The tangible downsides to modestly exceeding your magnesium needs are the cost of the magnesium and the potential for digestive distress with high doses of some forms of magnesium — oxide, especially.