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Magnesium Nutrition Summary for Dietitians

nutrition topics Nov 19, 2021

Written by Tracey Frimpong, RD, @thatblackrd

Medically Reviewed by Olivia Farrow, RD, MHSc

 

This article will summarize all of the must-know information about magnesium nutrition for registered dietitians.

 

Dietitian Success Center’s membership includes access to vitamin & mineral supplement guides, a comprehensive yet simplified reference for finding the best supplements for your clients. You can quickly find the different types of magnesium supplements in DSC’s magnesium supplement reference chart. Become a member of DSC today to get access to all of our supplementation reference guides.

 

Magnesium

Magnesium is an abundant mineral that the body requires daily. It is a cofactor in >300 enzyme systems that control a number of biochemical reactions in the body, including:

  • Muscle contraction
  • Nerve impulse conduction
  • Protein synthesis
  • Blood glucose control
  • Blood pressure regulation

There is emerging evidence that approximately two-thirds of the population in Westernized countries are not meeting their recommended daily allowance for magnesium, which can lead to a number of health issues

Common food manufacturing processes, like grinding wheat into flour or processing brown rice to white rice have reduced the magnesium content in many common foods. This trend of refining whole grains has been the greatest contributor to decreased magnesium intake.

The kidneys are mainly responsible for magnesium homeostasis, as they can excrete up to 120 mg of magnesium into the urine daily. When magnesium status is low, this urinary excretion decreases. 

 

Magnesium Deficiency

Magnesium deficiency can be linked to

1) Decreased intake - starvation, alcohol use disorder (AUD), and critically ill patients on parenteral nutrition may not consume enough dietary magnesium to meet their recommendations. Older adults tend to have lower dietary intakes, and magnesium absorption decreases while urinary magnesium excretion increases with age.

2) Drug-nutrient interactions - a variety of different medications can magnesium uptake

3) Gastrointestinal and/or renal losses - can occur due to acute or chronic diarrhea (e.g. in the case of a condition like Crohn's disease), hungry bone syndrome, acute pancreatitis, inherited tubular disorders such as Gitelman and Bartter, gastric bypass (especially the ileum), and other rare hereditary renal diseases. Those with type-2-diabetes and/or insulin resistance may have increased urinary magnesium excretion.

Magnesium deficiency can also cause hypocalcemia. Decreased magnesium levels can impair the release of parathyroid hormone (PTH). PTH helps regulate calcium levels and decreased PTH results in decreased calcium levels. Having adequate magnesium is essential for the absorption of calcium and deposition in bone, and additional magnesium increases calcium absorption.

Those with cardiac issues should be screened for magnesium deficiency, as deficiency can impact the electrical activity of the myocardium and vascular tone, putting patients at risk for cardiac arrhythmias.

 

Signs & Symptoms of Deficiency

  • Tremors
  • Tetany; positive Trouseau and Chvostek signs
  • Seizures
  • Vertical nystagmus
  • Apathy
  • Delirium
  • Coma
  • Electrocardiogram changes
  • Atrial fibrillation
  • Cardiac ischemia
  • Hypocalcemia
  • Hypoparathyroidism
  • Vertical nystagmus
  • Apathy
  • Delirium
  • Coma
  • Hypokalemia 

 

Food Sources of Magnesium

Fruits & Vegetables

  • Spinach, cooked: 83 mg magnesium per ½ cup
  • Swiss chard, cooked: 80 mg magnesium per ½ cup
  • Beans, yellow, cooked: 69 mg magnesium per ½ cup
  • Beet greens, boiled: 52 mg magnesium per ½ cup
  • Baked potato with skin: 49 mg magnesium per 1 medium potato
  • Banana: 32 mg magnesium per 1 medium banana
  • Papaya: 32 mg magnesium per 1 small papaya fruit
  • Avocado: 29 mg magnesium per ½ avocado
  • Guava: 12 mg magnesium per 1 guava fruit

Grains 

  • Muffin, raisin bran: 79 mg magnesium per 1 medium muffin
  • Cereal, oat bran, cooked: 65 mg magnesium per 1 cup
  • Quinoa, cooked: 63 mg magnesium per ½ cup 
  • Wheat bran: 45 mg magnesium per 2 tablespoons
  • Rice, brown, cooked: 44 mg magnesium per ½ cup
  • Pita, whole wheat: 44 mg magnesium per pita
  • Wheat germ, plain: 35 mg magnesium per 2 tablespoons
  • Bulgur, cooked: 31 mg magnesium per ½ cup
  • Rice, wild, cooked: 28 mg magnesium per ½ cup
  • Bread, whole wheat: 27 mg magnesium per slice
  • Cereal, bran flakes with raisins: 25 mg magnesium per ½ cup 

Meat, poultry, and fish

  • Mackerel, baked/broiled: 73 mg magnesium per 2.5 oz (75 g)
  • Atlantic salmon, baked/broiled: 28 mg magnesium per 2.5 oz (75 g)
  • Pork loin, broiled: 23 mg magnesium per 2.5 oz (75 g)
  • Chicken breast: 22 mg magnesium per 2.5 oz (75 g)
  • Halibut, baked/broiled: 21 mg magnesium per 2.5 oz (75 g)
  • Tuna, light, canned in water, drained, unsalted: 20 mg magnesium per 2.5 oz (75 g)

Milk, dairy, and soy foods

  • Tofu, cubed: 40-80 mg magnesium per ¾ cup (150 g)
  • Tempeh: 77 mg magnesium per 2/3 cup (100 g)
  • Soy beverage, fortified: 30 mg magnesium per 1 cup
  • Milk: 28 mg magnesium per 1 cup
  • Plain yogurt: 22 mg magnesium per ¾ cup 

Beans, peas, and lentils

  • Black-eyed peas, dry, cooked: 121 mg magnesium ¾ cup 
  • Soybeans, mature, cooked: 109 mg magnesium per ¾ cup
  • Lima beans, dry, cooked: 93 mg magnesium per ¾ cup
  • Black beans, cooked: 89 mg magnesium per ¾ cup
  • Navy beans, cooked: 80 mg magnesium per ¾ cup 
  • Soybeans (edamame), frozen, prepared: 73 mg magnesium per ¾ cup
  • Baked beans in tomato sauce: 64 mg magnesium per ¾ cup 
  • Lima beans, cooked: 59 mg magnesium per ½ cup 
  • Chickpeas, cooked: 58 mg per ¾ cup 
  • Kidney beans, dry, cooked: 55 mg magnesium ¾ cup 
  • Lentils, cooked: 53 mg magnesium per ¾ cup 

Peanuts, nuts, and seeds

  • Roasted pumpkin seeds, de-shelled: 317 mg magnesium per ¼ cup
  • Brazil nuts: 133 mg magnesium per ¼ cup 
  • Assorted nuts: 78-98 mg magnesium per ¼ cup 
  • Peanut butter, smooth: 55 mg magnesium per 2 tablespoons
  • Hazelnuts: 48 mg magnesium per ¼ cup
  • Pumpkin seeds, shell-on: 43 mg magnesium per ¼ cup
  • Sunflower seeds, de-shelled: 43 mg magnesium per ¼ cup
  • Sesame seeds: 33 mg magnesium per 1 tablespoon

Other

  • Unsweetened baking chocolate: 88 mg magnesium per 1 oz
  • Black strap molasses: 86 mg magnesium per 2 tablespoons
  • Semi-sweet chocolate chips: 59 mg magnesium per ¼ cup
  • Cocoa powder: 52 mg magnesium per 2 tablespoons
  • Sweet dark chocolate: 39 mg magnesium per 1 oz
  • Miso: 16 mg magnesium per 2 tablespoons

 

Dietary Factors that Influence Absorption

Approximately 40-50% of dietary magnesium is readily absorbed in the duodenum and jejunum

Absorption is reduced by:

  • Supplements high in fiber, folate or iron
    • Supplements should be separated by at least two hours
  • Food high in fiber, oxalate or phytate
    • Dietary fiber is known to contain phytates. Phytates are able to bind minerals such as magnesium and limit their absorption. Similarly, oxalates are anilines (have two negative charges) and because magnesium has two positive charges the two attract and oxalate depletes magnesium from the body

Diets high in any of these three should either

  1. Be supplemented with magnesium
  2. Avoid eating large quantities of foods with fiber, oxalate or phytate, and/or
  3. And/or eating a balanced diet with variety

 

Magnesium Supplementation

Individuals not meeting their dietary needs may require a supplement. There are many different types of magnesium supplements. The DSC magnesium supplement reference guide covers the most common types of magnesium supplements, the benefits and disadvantages of each, brand examples and cost comparisons.

 

Drug-Nutrient Interactions

Magnesium supplements can interact and inhibit the effectiveness of some medications listed below:

  • Loop and thiazide diuretics
  • Antibiotics
  • Bisphosphonates 
  • Proton pump inhibitors
  • High doses of Zinc supplements (~142 mg/day)
  • Antifungals (amphotericin)
  • Digitalis 
  • Chemotherapeutic drugs (cisplatin, cyclosporine) 

 

Contraindications for Supplementation

Patients with renal impairment and who have a creatinine clearance of less than 30 mL/minute (Stage III-IV Moderate to End Stage CKD) may be at risk of hypermagnesemia or heart block. Magnesium is excreted through the renal system, therefore those with renal insufficiency are at an increased risk; magnesium levels should be monitored before supplementation. 

 

Take-home Messages for Dietitians:

  • A balanced diet with variety will help to ensure magnesium needs are met, this includes vegetables, fruits, whole grains, dairy, and protein. 
  • If you suspect someone with decreased intake, on various medications, and/or have experienced gastrointestinal and renal losses, they are at a higher chance of not meeting their magnesium requirements. 
    • Serum magnesium may help to determine whether they require supplementation.
  • Those on magnesium supplements should be monitored for signs and symptoms of intolerance as high magnesium levels can cause adverse health effects. 

 

At DSC, we make it easier for dietitians and dietetic students to build expertise in topics including magnesium supplements. Our vitamin and mineral supplement guides, nutrition courses, ready-to-use client handouts, and community can help you feel more confident. 

Dietitian Success Center is THE professional development resource for dietitians and dietetic students. Our mission is to make it easier for dietitians and dietetic students to build expertise. We do this through evidence-based online nutrition courses, community, and ready-to-use client handouts. Plus - we give you the tools to start and grow your dietitian private practice!  

 

References

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Schwalfenberg, G. K., & Genuis, S. J. (2017). The Importance of Magnesium in Clinical Healthcare. Scientifica, 2017, 4179326. https://doi.org/10.1155/2017/4179326

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National Academies of Sciences. (2019, March 5). Dietary Reference Intakes (DRIs): Recommended Dietary Allowances and Adequate Intakes, Elements, Food and Nutrition Board, National Academies - Dietary Reference Intakes for Sodium and Potassium - NCBI Bookshelf. National Center for Biotechnology Information. https://www.ncbi.nlm.nih.gov/books/NBK545442/table/appJ_tab3/?report=objectonly. 

Gragossian A, Bashir K, Friede R. Hypomagnesemia. [Updated 2020 Sep 6]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK500003/ 

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Pronsky, Z. M., & Crowe, J. P. (2010). Food medication interactions (16th ed.). Food-Medication Interactions. 

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Charles Coudray, Christian Demigne╠ü, Yves Rayssiguier, Effects of Dietary Fibers on Magnesium Absorption in Animals and Humans, The Journal of Nutrition, Volume 133, Issue 1, January 2003, Pages 1–4, https://doi.org/10.1093/jn/133.1.1

Blancquaert, L., Vervaet, C., & Derave, W. (2019). Predicting and Testing Bioavailability of Magnesium Supplements. Nutrients, 11(7), 1663. https://doi.org/10.3390/nu11071663

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