Magnesium is a key mineral in human metabolism, and found in small to medium amounts in many of the World's Healthiest Foods. Vegetables (especially green leafy ones), nuts and seeds, and legumes are your best WHFoods sources for magnesium. We like to think of magnesium as the best supporting actor of the mineral kingdom. Like supporting actors in movies, magnesium doesn't get the notoriety of other nutrients like calcium or sodium, but it quietly plays every bit as important a role in human health. In fact, magnesium is necessary for more than 300 chemical reactions in the human body.
While magnesium is present in nutritionally important quantities in many of the foods featured on our site, average American diets frequently fail to contain an adequate supply of magnesium. In fact, adults average only 66% of the Daily Value (DV) for magnesium from their food intake (even though they get another 8% from supplements). This average intake level leaves U.S. adults about 100-125 milligrams short in the magnesium department. A likely reason for this deficient magnesium intake is the tendency of the average U.S. diet to focus predominantly on heavily processed convenience foods at the expense of the green leafy vegetables, nuts and seeds, and legumes that are among our best food sources of the mineral. Increasingly, researchers are becoming aware of a link between poor magnesium nutrition and risks of several important chronic conditions.
About 50 to 60% of a person's magnesium is stored in the bone, and as such, it plays a key role in bone metabolism. Researchers have found that even a mild ongoing magnesium deficiency can lead to a significant amount of bone loss.
Part of the way that this occurs is that when magnesium intake goes too low, levels of parathyroid hormone go down. This leads to a reduced absorption of calcium in the intestines, as well as increased loss of calcium and magnesium in the urine.
A link between adequate magnesium intake and improvements in bone mineral density has been established throughout the life cycle from adolescents all the way to elderly men and women. Researchers have also been able to induce osteoporosis in animal studies through low-magnesium diets—diets that would be similar (at least with respect to %DV intake) to the routine low-grade magnesium-deficient diets humans commonly eat.
We do not know yet whether dietary magnesium has the same level of relative importance as vitamin D or calcium in the maintenance of bone. But the existing research, together with the frequency of magnesium-deficient diets, suggests that low magnesium may be an underappreciated contributor to bone loss.
One critical task performed by our cells is energy production. This task is a complicated one and involves dozens of chemical reactions, all intimately related and flowing in a very special sequence. Unless these chemical reactions can take place in the exact needed order, we don't get the energy production that we need from our cells. Within this energy production sequence, magnesium plays an important role. Many of the chemical reactions cannot take place unless magnesium is present as "co-factor" for the enzymes that allow energy production to occur. Enzymes are protein molecules that make it easier for chemical reactions to occur throughout the body, including chemical reactions related to energy production. Co-factors are nutrients that must be coupled together with enzymes in order for those enzymes to function.
Based on magnesium's role in energy production within our cells, low levels can be one of the potential contributory factors causing fatigue. Because magnesium deficiency is hard to test via blood work or equivalent laboratory testing, it is not clear what percentage fatigue symptoms are caused or contributed to by magnesium. However, if you look at changes in fatigue symptoms from studies in which participants were given magnesium supplements at levels at least as high as the Recommended Dietary Allowance (RDA) and you couple these study results with information we already know about low intake of magnesium by the average U.S. adult you can draw a conclusion that low dietary intake of magnesium increases our risk of fatigue.
Receptors are special molecules along our cell membranes that help chemical messages enter and leave our cells. All of the cells in our body have membrane receptors. Among the best studied are receptors found along the membranes of our brain cells. One of these brain cell receptors is referred to as the NMDA receptor. (NMDA stands for N-methyl-d-aspartate.) The NMDA receptor is noted for being the site where some anesthetics and recreational drugs affect our brain function.
Magnesium plays a key role in the activity of our NMDA receptors. Research studies have shown that when magnesium in our diet is low, we have increased risk of depression, and this increased risk is likely related to problems with our NMDA receptors. A long history of published evidence demonstrating that treatment with magnesium can have anti-depressant effect—this was first published in 1921—suggests that low magnesium can actually cause depression.
A diet low in magnesium has been linked to unwanted increases in the inflammatory process. While some amount of inflammation is necessary to support normal immune function and tissue repair after injury, chronic and low-grade inflammation has increasingly been tied to increased risk of heart disease, obesity, and diabetes.
Restoring magnesium levels to recommended intakes has led to normalization of inflammation in clinical trial settings. For example, one large clinical trial found that a Nordic diet strategy—a diet rich in fish, whole grains, and vegetables as sources of magnesium—led to a suppression of the important inflammatory trigger interleukin-1.
Magnesium is a co-factor for over 100 enzymes involved in the control of blood sugar and glucose metabolism. As such, low magnesium status would be expected to have wide-ranging adverse effects on blood sugar control. Researchers have been able to demonstrate both worsening blood sugar control in individuals with low magnesium status and improvements in blood sugar when these low levels begin to normalize. We address this subject in more detail in the section entitled "Other Circumstances That Might Contribute to Deficiency" section.
While there are few food sources that are strikingly high in magnesium content, a large number of foods contain relevant amounts of this important mineral. In fact, almost half of our World's Healthiest Foods are rated as good, very good, or excellent sources of magnesium. Only three of our WHFoods qualify as an excellent source of magnesium—spinach, Swiss chard, and beet greens. Joining them as very good sources are three additional foods (pumpkin seeds, turnip greens, and summer squash).
Our top 20 WHFoods for magnesium also include numerous legumes, nuts, and seeds. Top legumes for magnesium are navy beans, tempeh (fermented soybeans), pinto beans, lima beans, and kidney beans. The top magnesium-rich nuts and seeds are pumpkin seeds, sesame seeds, sunflower seeds, cashews, and almonds. Among our grains, barley, buckwheat, brown rice, quinoa, and millet also rank in our top 25 magnesium foods. Although a few fruits are ranked as good sources of magnesium, you typically wouldn't turn to fruits for your magnesium, nor to dairy products nor meats.
Within the legume category, we'd like to mention one special soybean-based product that can be significantly higher in magnesium. When soybeans are made into tofu, one specific form of tofu—usually called "nigari tofu" or "tofu prepared from nigari flakes"—typically contains higher amounts of magnesium that other forms of tofu. That's because magnesium chloride is usually used as a coagulant to curdle the soy milk in this form of tofu.
Drinking water can be surprisingly rich in magnesium, but the magnesium content of water varies dramatically. Generally speaking, water that is allowed to percolate through magnesium-rich soil and rock can pick up a large amount of magnesium. We've seen bottled mineral waters, for example, that provide over 100 milligrams of magnesium per liter. That level means 25% of the Daily Value (DV) in one liter bottle of water. We've also seen municipal water supplies in the U.S. that provide nearly 50 milligrams of magnesium per liter. However, we've also seen reports on municipal water supplies in the U.S. that contain no magnesium whatsoever. If you are drinking tap water from your local water supply, it will typically be your local water district or your local utility district that is charged with monitoring your drinking water quality, including its magnesium content. They'll be able to provide you with actual numbers. Usually these numbers will be reported in terms of parts per million or ppm. (So that know how to convert the numbers, here are two examples: If your local drinking water contains 9 ppm of magnesium, that amount is the same as 9 milligrams per liter while if it contains 90 ppm, that amount is the same as 90 milligrams per liter.)
|World's Healthiest Foods ranked as quality sources of|
|Swiss Chard||1 cup||35.0||150.50||36||18.4||excellent|
|Beet Greens||1 cup||38.9||97.92||23||10.8||excellent|
|Pumpkin Seeds||0.25 cup||180.3||190.92||45||4.5||very good|
|Summer Squash||1 cup||36.0||43.20||10||5.1||very good|
|Turnip Greens||1 cup||28.8||31.68||8||4.7||very good|
|Sesame Seeds||0.25 cup||206.3||126.36||30||2.6||good|
|Black Beans||1 cup||227.0||120.40||29||2.3||good|
|Sunflower Seeds||0.25 cup||204.4||113.75||27||2.4||good|
|Navy Beans||1 cup||254.8||96.46||23||1.6||good|
|Pinto Beans||1 cup||244.5||85.50||20||1.5||good|
|Brown Rice||1 cup||216.4||83.85||20||1.7||good|
|Lima Beans||1 cup||216.2||80.84||19||1.6||good|
|Green Peas||1 cup||115.7||53.72||13||2.0||good|
|Collard Greens||1 cup||62.7||39.90||10||2.7||good|
|Brussels Sprouts||1 cup||56.2||31.20||7||2.4||good|
|Winter Squash||1 cup||75.8||26.65||6||1.5||good|
|Green Beans||1 cup||43.8||22.50||5||2.2||good|
|Bok Choy||1 cup||20.4||18.70||4||3.9||good|
|Mustard Greens||1 cup||36.4||18.20||4||2.1||good|
|Mustard Seeds||2 tsp||20.3||14.80||4||3.1||good|
|Romaine Lettuce||2 cups||16.0||13.16||3||3.5||good|
|Bell Peppers||1 cup||28.5||11.04||3||1.7||good|
Density>=7.6 AND DRI/DV>=10%
Density>=3.4 AND DRI/DV>=5%
Density>=1.5 AND DRI/DV>=2.5%
Magnesium—like all minerals—is an element that has always existed on the earth, in foods, and in our body. In this context, some people look at magnesium (and other minerals) as not only being forever unchanged in the history of the planet but also as being unchanging in its very nature as an element. From a food perspective, however, we think it makes more sense to treat magnesium as a nutrient that can undergo change, because magnesium is not usually found in food in its simple elemental form. For example, in drinking water, magnesium is often found in the form of dissolved salts like magnesium chloride or magnesium sulfate. In plant foods, it often occurs as part of the chlorophyll molecule. (Chlorophyll is a green pigment that not only gives so many plants their color but also allows them to turn sunlight into energy.) These different food forms of magnesium can be changed through cooking.
We reviewed several recent studies in which fresh vegetables or legumes were boiled for relatively short periods of time and then analyzed for changes in magnesium content. In one study, French beans, broad beans, and peas were boiled for eight to twelve minutes, and in a second study, spinach and kale were boiled for two to three minutes. Especially when a vegetable is boiled very briefly prior to freezing, this process is often referred to as "blanching." (The spinach and kale referred to above were described as being "blanched" by the researchers conducting the study.) In the case of French beans, spinach, and kale, researchers found between 20-30% magnesium loss due to boiling, and in the case of broad beans and peas, a loss of 2-10%.
You'll find specific tips on food storage in the "How to Select and Store" sections of our individual food profiles. Since legumes, nuts, and seeds are among our best WHFoods sources for magnesium and since these foods can usually be stored for relatively long periods of time, stability problems with magnesium in stored foods are not typically a concern.
While not appearing in our top WHFoods sources for magnesium, whole grains can still be a good source of this mineral. However, much of their magnesium content can be lost through the refining process. For example, whole wheat flour contains about six times as much magnesium by weight compared to white flour. (By the term "white flour," we are referring to whole wheat that has undergone 60% extraction during milling such that 40% of the original grain—mostly the bran and germ portion—has been removed during milling. Unlike some of the vitamins and minerals that are reduced or totally lost during grain processing (at least 19 nutrients undergo processing loss), magnesium is not added back into processed grain flours to "enrich" the final grain products. The Food and Drug Administration (FDA) has only set standards of enrichment for four nutrients lost during grain processing (vitamins B1, B2, B3 and the mineral iron). Even though magnesium is lost during grain processing, no standard has been set by the FDA for magnesium enrichment of grain products. For this reason, if you do decide to incorporate grains into your meal plan as a possible magnesium source, whole grain products are the best way for you to get as much magnesium as possible from your grains.
In the U.S., the risk of dietary deficiency of magnesium is very high. In fact, the average U.S. adult falls well short of the 400 mg per day Daily Value (DV) and consumes only 266 milligrams of magnesium from food. Since some foods are fortified with added magnesium, the average U.S. adult gets an additional 10 milligrams of magnesium from fortification. That brings the food total to 276 milligrams, with another 34 milligrams (on average) from dietary supplements, for a grand total of 310 milligrams —still only three-quarters of the DV.
Among the top ten food contributors to America's total magnesium intake are items like coffee, beer, and French fries. It's not that these foods are good magnesium sources, just that we eat (or drink) a lot of them.
Diets rich in green leafy vegetables, legumes, nuts, and seeds —and to a lesser extent, whole grains —would be the best way for you to limit your risk of having magnesium deficiency. Two servings from each of these categories daily could put you at or above the DV for magnesium.
Here's an example of some everyday food choices that would provide you with the DV for magnesium:
One of the most important contributors to deficiency of magnesium is high blood sugar, including diabetes. Obesity is related to magnesium deficiency, too, but this relationship is currently thought to be the result of blood sugar elevations.
Surprisingly, it looks like the relationship between low magnesium diets and high blood sugar goes in both directions—in other words, a diet low in magnesium-rich foods tends to lead to poor blood sugar control. This poor blood sugar control in turn exacerbates the low magnesium level. To break up this unwanted sequences of events , a group of nutritionists affiliated with Tufts University suggested that older adults should be counseled about the importance of eating green vegetables, legumes, and whole grains as sources of magnesium.
The rate of magnesium deficiency goes up with age, with average intakes in the elderly dropping by 25% or more from middle-aged adults. African-Americans have much higher rates of magnesium deficiency than Caucasians.
Older patients with heart failure and chronic obstructive pulmonary disease (COPD) also have been found to have high risks of magnesium deficiency. In both conditions, improving magnesium levels has been found to lead to health benefits in smaller research trials.
Medications can deplete magnesium levels as well. In particular, people taking diuretics should talk to their doctor about the importance of ensuring good supply of dietary magnesium.
Magnesium, calcium, and phosphorus have a complex relationship with respect to absorption in the intestine. How much of each of these nutrients goes into the blood stream versus being lost in the stool is variable by relative amount, hormonal balance, and even time of day.
In general, more magnesium tends to reduce phosphorus absorption. This is not necessarily a problem, since the average U.S. diet does not correspond with phosphorus deficiency.
The relationship between calcium and magnesium has been of longstanding interest in research. Scientists have long been aware that these two minerals belong to the same family of elements (alkali earth metals), take on the same electrical charge (2+), and have a predictable ratio in different types of soil. However, only in recent studies have we learned more about specific details about calcium and magnesium in terms of dietary intake and absorption rate. It turns out that absorption of magnesium from our intestine depends not only on the amount of magnesium that is present but also on the amount of calcium that is present, because the cells lining our intestine have a single spot (called the CaSR receptor) for absorbing these minerals. In practical terms, these circumstances suggest that our diet needs to be balanced in terms of magnesium, calcium, and the ratio of these two minerals.
At the World's Healthiest Foods, we recommend 400 milligrams of daily magnesium (the Daily Value amount) and 1,000 milligrams of daily calcium (the Dietary Reference Intake level for women 19-50 years of age). These recommendations would combine to form a calcium:magnesium ratio of 2.5:1. Since the average U.S. adult only averages 266 milligrams of magnesium intake from food, as compared with approximately 1,000 milligrams of calcium from food (about 1,150 milligrams for men 20 years and older and about 900 milligrams for women 20 years and older), an average calcium:magnesium ratio in the U.S. diet would be approximately 3.75:1, or 50% greater than a ratio based on our WHFoods recommendations. Since many people in the U.S. (especially women) don't currently consume enough calcium in their diet, it would be a great mistake for most people to try and balance their calcium:magnesium ratio by cutting back on calcium-rich foods. So in order to achieve a lower ratio, increased emphasis on magnesium-rich foods seems like the best approach.
The risk of dietary toxicity from magnesium for healthy adults is very low. Too much magnesium from supplements has been linked to loose stools, but this is unlikely to occur from foods alone. Reflecting this low risk, the Institute of Medicine (IOM) at the National Academy of Sciences has established no upper limit for dietary intake of magnesium.
People with renal failure, especially if they are on dialysis, will likely need to work with a trained nutrition specialist to obtain safe recommendations about magnesium intake. The recommendations on this site are not appropriate for patients on dialysis.
In 1997, the National Academy of Sciences established a set of Dietary Reference Intakes (DRIs) for magnesium that included age and gender specific Recommended Dietary Allowances (RDAs) for magnesium. Note that the recommendation for infants from 0-12 months of age is an Adequate Intake (AI) recommendation rather than an RDA. The AIs and RDAs are as follows:
The U.S. Food and Drug Administration (FDA) set 400 milligrams of magnesium as its recommended daily amount, or Daily Value (DV). DVs are the standards that you see on the Nutrition Facts Panel for a packaged food. We used this magnesium DV as our WHFoods recommended daily amount.