The Bad News about Magnesium Food Sources
With magnesium deficiencies on the rise, a common question is, “How do you get enough magnesium in your diet?”
Magnesium content in vegetables has seen declines from 25-80%.
Yet — while it’s always important to seek out magnesium rich foods — many are unaware of the drastic declines in food-based nutrient sources that have occurred over the last century. These factors, coupled with poor food choices, now cause many health professionals to question the ability to get sufficient magnesium exclusively from food.
Magnesium content in vegetables has seen declines from 25-80% since pre-1950 figures, and typical grain refining processes for bread and pasta remove 80-95% of total magnesium.
What is happening to our food sources, and how is it shaping the rise of chronic diseases such as hypertension and metabolic disorder?
Foods High In Magnesium
Magnesium food sources were once commonly consumed, but have diminished in the last century due to industrialized agriculture and changing diets.
The average American diet contains barely over 50% of the conservative US recommended daily allowance (RDA) for magnesium1 2 , and roughly three quarters of the population consumes a magnesium insufficient diet.1 3 4 5
The foods magnesium is found in include:
- Beans and nuts
- Whole grains such as brown rice and whole wheat bread
- Green leafy vegetables
Given current food preferences, however, it’s easy to see how it’s hard to achieve 100% of RDAs for magnesium.
% Daily Value in Magnesium Containing Foods
The majority of good magnesium sources contain only about 10% or less of recommended daily amounts, as seen in a list of the magnesium content in common food sources of magnesium. Those that do contain more, such as certain nuts, fish and whole grains, are often eaten in too small quantities by the average person.
But, in fact, percent daily value figures are just averages. For every individual:
- Absorption rates can vary, and according to studies can sometimes be as low as 20%.6 7
- Factors can interfere with magnesium absorption, including phytic and oxalic acid found in certain foods, prescription drugs, age, and genetic factors.
The Problem With Dietary Magnesium
Why is a high magnesium diet harder to achieve today? What is changing our vitamin and mineral food sources?
There three basic reasons we can’t get enough magnesium in the diet:
- Reduced levels due to processing.
- Reduced levels due to soil conditions.
- Changes in eating habits.
Processed Foods and the Magnesium Rich Diet
Food processing essentially separates plant food sources into components, both for ease of use and to reduce spoilage.
In processing grain into white flour, the bran and the germ are removed. In processing seeds and nuts into refined oils, the oils are super-heated and the magnesium content is strained out or removed through the use of chemical additives.
It is these removed portions of the plant that often contain the highest amount of minerals such as magnesium.
- Refined oils remove all magnesium. The result of oil refining is a zero magnesium product. Safflower seeds, for example, contain 680 mg of magnesium per 1,000 calories. Safflower oil lacks magnesium entirely.8
- Refined grains remove 80-97 percent of magnesium.9 At least twenty nutrients are removed in refining flour. And only five are put back in when refined flours are “enriched”.10 Magnesium is not one of them.
- Refined sugar removes all magnesium. Molasses, which is removed from the sugar cane in refinement, contains up to 25% of the RDA for magnesium in one tablespoon. Sugar has none.
An unfortunate additional side effect of the processing of these foods is, in fact, an increase in calories by volume. For example, when wheat is refined into white flour, calories are increased by about 7 percent.8
The typical American convenience food diet of fast food, pizzas, pastries, cookies and fried foods consists almost exclusively of refined grains, oils and sugars. Over time, excess consumption of these foods can lead to both obesity and magnesium deficiency, a potentially fatal combination.
Dr. Mildred Seelig, author of The Magnesium Factor, spells it out clearly:
If restaurant, homemade, or store-bought food contains fat, refined flour, and/or sugar as one or more of the major ingredients, it is a low-magnesium, and quite possibly a high-calorie, food. A steady diet of such foods, year after year, can produce magnesium deficit and, with it, metabolic syndrome X—a major factor in heart disease.”8
Where Do Foods Containing Magnesium Come From? …From Soil Containing Magnesium
It is well known among experts that the quality of our crops is decreasing. In 2004, the Journal of the American College of Nutrition released a study which compared nutrient content of crops at that time with 1950 levels. Declines were found as high as 40%.11
Dr. Donald Davis, lead researcher for the study, offers one explanation for the dramatic declines:
During those 50 years, there have been intensive efforts to breed new varieties that have greater yield, or resistance to pests, or adaptability to different climates. But the dominant effort is for higher yields. Emerging evidence suggests that when you select for yield, crops grow bigger and faster, but they don’t necessarily have the ability to make or uptake nutrients at the same, faster rate.”12
Several similar studies have been done using food tables from the USDA in the US, and Food Standards Agency in the UK. Declines found for magnesium were significant:
|Magnesium Content||Percentage Decline||Percentage Decline|
|Average across fruits and vegetables studied||21%||35%|
|Collard Greens||84%||not available|
These declines are not limited to vegetable crops. A study by David Thomas published in Nutrition and Health examined average nutritional content of foods across food categories using the UK government’s Composition of Food tables.
Thomas found consistent declines in magnesium content:
- Vegetables declined by 24% between 1940 and 1991.
- Fruit declined by 17%.
- Meat declined by 15%.
- Cheeses declined by 26%.17
Government agencies and food industry organizations have questioned the reliability of these results, citing the possibility that changes in measurement techniques may account for the differences. But Dr. Joel Wallach of the Longevity Institute refutes this claim.
Were these differences the result of errors in measurement, explains Dr. Wallach, such errors would be present consistently across food types and categories. Yet when comparing USDA food tables between 1963 and 1998, Wallach reports that:
- Crops whose harvesting practices have not changed historically showed stable vitamin and mineral content over the years.
- By contrast, significant reductions in vitamin and mineral content were consistently present in crops that are produced by more intensive, industrialized farming practices.18
Our crops’ lack of magnesium and other nutrients has a direct impact on the ability to achieve sufficient magnesium in the diet.
Ultimately, even those who seek out a balanced high magnesium diet with magnesium-rich vegetables and whole grains may not be able to rely upon food alone to provide sufficient magnesium levels.
Pesticides Destroy Organisms That Provide Nutrients to Plants
Experts link vitamin and mineral depletion in the soil to use of pesticides and fertilizers.
Today’s soils produce vegetation with dramatically reduced vitamin and mineral content.
Though it was believed initially that pesticides would work simply to rid farmland of unwanted weeds and pests, it was soon learned that their use was causing irreversible damage. Vitamin-fixing bacteria in the soil, as well as earthworms, natural soil aerators and fertilizers, were being first reduced and then extinguished from American crop land.
Without this living environment, soils produce vegetation with dramatically reduced vitamin and mineral content.
For example, vegetarians are commonly advised to supplement their diet with certain B vitamins, especially B12, as an all-vegetable diet has been shown to be deficient in these vitamins. What is less commonly known is that in the past these vitamins were in fact found commonly in root vegetables due to the action of living, beneficial bacteria in the soil.
Today’s soils, which have essentially eradicated these bacteria populations, cannot now be relied upon to provide B12 in any significant amount. However, Swiss researchers with the Institute of Plant Sciences in Zurich have demonstrably shown that a return to organic farming practices can reintroduce B12 content. The long term use of organic fertilizers (rather than synthetic) more than doubled the B12 content of spinach and tripled the B12 content of barley.19
Fertilizers Diminish Mineral Absorption
Modern fertilizers are a convenient substitute for centuries old crop rotation practices which prevented farmland from becoming depleted through repetitive use. Yet they do little to improve the vitamin and mineral content of crops, and in many cases actually worsen it.
In fact, minerals are even more susceptible to the reductions in soil quality than vitamins. Whereas many vitamins can actually be produced by growing plants themselves, if minerals are not first present in the soil they will not be present in the produce grown there.9
And because mineral content of crops is in no way regulated, modern industrialized farming practices typically do not concern themselves with this standard of quality when choosing fertilizers.
Potash, a commonly-used potassium fertilizer easily taken up by plants, actually reduces the amount of both magnesium and calcium absorbed by the plant. And modern nitrogen-based fertilizers have a tendency to make crops bulkier, yet nutrient poor. Mother Earth News recently interviewed agricultural expert Charles Benbrook, Ph.D., who explained the phenomenon:
High nitrogen levels make plants grow fast and bulk up with carbohydrates and water. While the fruits these plants produce may be big, they suffer in nutritional quality.20
The effect is one which is beneficial to the producer, but not the consumer. Consumers pay more for heavier, water-laden produce that contains less vitamins and minerals.
Bottom Line: An Adequate Magnesium Diet Goes Beyond Food Sources
Agricultural industry emphasizes those fertilizers that improve the “look” of the harvest, and not the actual nutritional value of the produce itself.
- It’s possible to produce healthy-looking plants with low content of vitamins and minerals.
- The actual magnesium content of produce grown today is drastically lower than in pre-industrial times, and varies widely depending on farming practices, quality of soil, and storage and transportation methods.
- Food tables are at best averages, and no current regulations require testing or monitoring of nutritional content of produce or meat sources.
The wide variability in the vitamin and mineral content of foods debunks the myth that you can get all the nutrients you need through a balanced healthy diet. Unfortunately for the majority of people in industrialized nations, the old adage, “You can get all your vitamins and minerals from food” is longer true.
In fact, the average American today is deficient in at least three vital nutrients.21
Noted magnesium researchers Burton and Bella Altura have linked ongoing declines in magnesium intake with increased incidence of life-threatening disease. In their 2006 report to the International Magnesium Symposium held in Osaka Japan, they state:
The data accumulated so far indicate that magnesium deficiency caused either by a poor diet or errors in magnesium metabolism may be a missing link between diverse cardiovascular risk factors and atherogenesis.”2
The body is equipped to absorb dietary magnesium sources, and even in cases of mild or severe deficiencies it is always recommended that you include magnesium-rich foods in your diet. Yet with the state of modern agri-business today and the increasing risks to health and longevity, relying upon magnesium food sources alone can be a risky proposition.
How do you choose a magnesium supplement? Learn how to sort out the good from the bad.
Watch magnesium video interviews — powerful commentary on the why and how of magnesium.
Chart of Magnesium Rich Foods
The following a list of the magnesium content in common food sources of magnesium is sorted by milligrams magnesium per gram of food content.
|Serving Size, Common Units||Serving Size, Grams||Milligrams Magnesium||Milligrams Magnesium per Gram||% Daily Value (DV)|
|Cocoa, unsweetened||2 tbsp.||10||52||5.24||14%|
|Bran Breakfast Cereal, ready to eat||1 oz.||28||78||2.78||19%|
|Cashews, dry roasted||1 oz.||28||73||2.61||18%|
|Pumpkin Seeds, roasted||1 oz.||28||73||2.61||18%|
|Peanuts, dry roasted||1 oz.||28||49||1.75||12%|
|Peanut Butter||2 tbsp.||32||49||1.53||12%|
|Whole Wheat Bread, homemade||1 slice||28||37||1.32||9%|
|Navy Bean Sprouts, raw||1 oz.||28||28||1.01||7%|
|Spinach, boiled||1/2 cup||90||79||0.87||20%|
|Whole Wheat Bread, store bought||1 slice||28||23||0.82||6%|
|Coffee, espresso||2 oz.||60||48||0.80||12%|
|Spinach, raw||1 cup||30||24||0.79||6%|
|Quinoa, cooked||1/2 cup||92.5||59||0.64||15%|
|Milk Chocolate||1 oz.||28||18||0.63||4%|
|Soybeans, boiled||1/2 cup||90||54||0.60||14%|
|Black-Eyed Peas (Cowpeas), boiled||1/2 cup||87.5||46||0.52||12%|
|Buckwheat Groats (Kasha), cooked||1/2 cup||84||43||0.51||11%|
|Parsley, raw||1 oz.||28||14||0.50||3%|
|Lima Beans, boiled||1/2 cup||94||40||0.43||10%|
|Acorn squash, baked||1/2 cup||102.5||44||0.43||11%|
|Swiss Chard||1/2 cup||175||75||0.43||19%|
|Artichokes||1 whole medium||120||50||0.42||13%|
|Egg, fried||1 whole large||46||18||0.39||3%|
|Bacon, pan-fried||3 oz.||85||31||0.36||8%|
|Pork Tenderloin, broiled||3 oz.||85||31||0.36||8%|
|Okra, boiled||1 cup||160||58||0.36||14%|
|Bulgur Wheat, cooked||1/2 cup||91||29||0.32||8%|
|Whole Wheat Spaghetti||1/2 cup||70||21||0.30||6%|
|Parsnips, boiled||1/2 cup||78||23||0.29||6%|
|Chicken Breast, roasted||3 oz.||85||24||0.29||6%|
|Ground Beef, pan browned||3 oz.||85||24||0.28||6%|
|Broccoli, boiled||1/2 cup||78||16||0.21||4%|
|Pasta Sauce||1/2 cup||128||27||0.21||7%|
|Potatoes, boiled without skin||1 cup||156||31||0.20||8%|
|Milk, 2%||1 cup||244||27||0.11||7%|
|Coffee, from grounds||6 oz.||178||5||0.03||1%|
- Institute of Medicine. Dietary Reference Intakes for Calcium, Phosphorous, Magnesium, Vitamin D, and Fluoride. Washington, DC: National Academy Press; 1997. [↵] [↵]
- Altura BM, Altura BT. Magnesium: Forgotten Mineral in Cardiovascular Biology and Therogenesis. In: International Magnesium Symposium. New Perspectives in Magnesium Research. London: Springer-Verlag; 2007:239-260. [↵] [↵]
- World Health Organization. Calcium and Magnesium in Drinking Water: Public health significance. Geneva: World Health Organization Press; 2009. [↵]
- Pao EM, Mickle SJ. Problem nutrients in the United States. Food Technology. 1981:35:58-79. [↵]
- King DE, Mainous AG 3rd, Geesey ME, Woolson RF. Dietary magnesium and C-reactive protein levels. Journal Of The American College Of Nutrition. 2005 Jun;24(3):166-71. Available from: MEDLINE with Full Text, Ipswich, MA. Accessed November 6, 2009. [↵]
- Bohn T. Dietary Factors Influencing Magnesium Absorption in Humans. Current Nutrition & Food Science. 2008;4:53-72. [↵]
- McCarthy J, Kumar R. Divalent Cation Metabolism: Magnesium. In: Schrier R, series editor. Atlas of Diseases of the Kidney. Volume 1. Wiley-Blackwell; 1999: 4.1-4.12. [↵]
- Seelig M, Rosanoff A. The Magnesium Factor. New York: Avery; 2003. [↵] [↵] [↵]
- Dean C. The Magnesium Miracle. New York: Ballantine Books; 2007. [↵] [↵]
- Lieberman S, Bruning N. The Real Vitamin & Mineral Book. New York: Avery; 2007. [↵]
- Davis D, Epp M, Riordan H. Changes in USDA Food Composition Data for 43 Garden Crops, 1950 to 1999. Journal of the American College of Nutrition. 2004;23(6):669-682. Available at: http://www.jacn.org/cgi/content/full/23/6/669. Accessed November 11, 2009. [↵]
- Study suggests nutrient decline in garden crops over past 50 years. University of Texas at Austin. 2004. Available at: http://www.utexas.edu/news/2004/12/01/nr_chemistry/. Accessed November 11, 2009. [↵]
- Worthington V. Nutritional Quality of Organic Versus Conventional Fruits, Vegetables, and Grains. Journal of Alternative and Complementary Medicine. 2001;7(2):161-173. [↵] [↵]
- Bergner P. The Healing Power of Minerals, Special Nutrients and Trace Elements. Rocklin, CA: Prima Publishing Co., 1997:46–75. [↵]
- Vegetables without Vitamins. LE Magazine. March 2001. Available at: http://www.soilandhealth.org/06clipfile/0601.LEMag/LE%20Magazine,%20March%202001%20-%20Report%20Vegetables%20Without%20Vitamins.htm Accessed November 11, 2009 [↵]
- Mayer A-M. Historical changes in the mineral content of fruits and vegetables: A cause for concern? British Food Journal. 1997;99(6):207–11. [↵]
- Thomas, D. The Mineral Depletion of Foods Available to us as a Nation (1940-2002). Nutrition and Health. 2007;19:21–55. [↵]
- Wallach, J. Our Food is Deprived of minerals: the Proof. Longevity Institute Newsletter. 2006; Newsletter 16. Available at: http://www.longevinst.org/nlt/newsletter16.htm. Accessed November 11, 2009. [↵]
- Mozafar A. Enrichment of some B-vitamins in plants with application of organic fertilizers. Plant and Soil. December 1994;167(2):305-311. [↵]
- Long C, Keiley L. Is Agribusiness Making Food Less Nutritious? Mother Earth News. July 2004. Available at: http://www.motherearthnews.com/Real-Food/2004-06-01/Is-Agribusiness-Making-Food-Less-Nutritious.aspx. Accessed November 11, 2009. [↵]
- Halweil B. Still No Free Lunch: Nutrient Levels in the U.S. Food Supply Eroded by Pursuit of High Yields. The Organic Center; September 2007. Available at http://www.organic-center.org/reportfiles/Yield_Nutrient_Density_Final.pdf. Accessed February 12, 2010. [↵]