Key Concepts

  • 75% of Americans are likely to be deficient in magnesium
  • Adequate intake – 400-420 mg/day for men & 310-320 mg/day for women
  • Tolerable Upper Intake Limit (UL) – 350 mg/day through supplementation only; magnesium from food can be excreted and has no UL
  • Magnesium can be absorbed through the skin (epsom salt, ocean water)
  • Magnesium glycinate & Magnesium aspartate – supplemental forms that are well absorbed and generally well tolerated
  • Magnesium sulfate & magnesium oxide – induce bowel movements
  • Cooking, soaking, sprouting, & fermenting increase absorption of magnesium
  • Food Sources – Dark chocolate, whole grains, green leafy vegetables, nuts and seeds, legumes, fish
  • Magnesium Supplement – $0.23/serving
  • Magnesium Glycinate 120 mg – $0.17/serving
  • Epsom Salt – $1.50/bath

Adequate Intake (AI)

  • Adult male (19-30) – 400 mg
  • Adult female (19-30) – 310 mg

Adequate intake of magnesium is variable with age. Older populations need more, younger populations need less. Pregnancy and lactation increase the need for magnesium.


Magnesium is involved in over 300 biochemical processes. Magnesium is a catalyst for ATP production, is essential in cell membrane stabilization (ion channel regulation), in the synthesis of proteins, lipids, and nucleic acids, in DNA synthesis, muscle contraction, blood clotting, and blood pressure regulation.


It is estimated that 75% of Americans are deficient in magnesium. Although many foods contain magnesium, it is often bound to phytic acid, an anti-nutrient that decreases the ability to absorb magnesium. Due to monocropping and industrial farming, the amount of magnesium in soils and in the foods growing from those soils has been decreasing since the 1950’s.

High doses of supplemental zinc may interfere with the absorption of magnesium. Large increases in dietary fiber intake have been shown to decrease magnesium utilization. Higher protein intake may increase magnesium absorption and lower protein intake may decrease magnesium absorption. Severe magnesium deficiency can impede vitamin D and calcium homeostasis.

Magnesium is systemically absorbed through the skin although to what extent still remains unclear. Magnesium absorbed from the ocean or from an epsom salt bath will contribute to the body’s total magnesium levels.

Magnesium deficiency can lead to neuromuscular excitability. During magnesium depletion, intracellular sodium and calcium rise while magnesium and potassium fall. Muscle cramps/twitching, restless leg syndrome, cardiac dysrhythmias, and hypertension can ensue because of this. Magnesium deficiency can also lead to nausea, vomiting, and diarrhea, and have a negative impact on bone health.

Magnesium deficiency has been associated with increased risk of cardiovascular disease, osteoporosis, and metabolic disorders (including hypertension & type-2 diabetes).

Toxicity/Excess/Upper Limit (UL)

The tolerable upper intake level (UL) for magnesium is 350 mg per day for adults and that is only through supplementation. There is no UL for magnesium found in foods because excess magnesium from foods is eliminated by the kidneys and excreted in the urine. High doses from supplementation can cause diarrhea, dehydration, nausea, abdominal cramping, and impaired kidney function.


It appears that the best way to supplement with magnesium is in divided doses throughout the day, say 50 mg in the afternoon and 50 mg in the evening. It does not take magnesium long to build up in the system. And as I stated before excess can cause gastrointestinal (GI) distress. Calcium and magnesium inhibit the absorption of one another as they are both divalent cations, so it makes sense to take them at different times during the day.

Magnesium can be absorbed through the skin. Epsom salt is magnesium sulfate and its use tends to promote relaxation, to ease muscle aches and pains, and may be useful in recovering from exercise.

If magnesium sulfate is taken internally it can induce a bowel movement. Magnesium oxide can as well.

Magnesium glycinate is absorbed well orally; it is magnesium attached to glycine. Glycine is an inhibitory neurotransmitter and may support liver health. Magnesium aspartate also appears to be absorbed well. Magnesium citrate is a less expensive form of magnesium but may cause GI distress in some individuals.

Supplemental magnesium has been used to improve sleep quality, reduce anxiety, to promote relaxation, and to reduce the severity and frequency of migraines.

Magnesium supplementation has high potential for toxicity, especially those with kidney disease.

Food Sources

  • Dark chocolate, 1/2 bar – 115mg – 31% DV
  • Hemp seed, 30 g – 192mg – 48% DV
  • Almonds, dry, roasted, 1 oz – 80mg – 20% DV
  • Spinach, boiled, 1/2 cup – 78mg – 20% DV
  • Cashews, dry roasted, 1 ounce – 74 mg – 19% DV
  • Black beans, cooked, ½ cup – 60 mg – 15% DV
  • Rice, brown, cooked, ½ cup – 42 mg – 11% DV
  • Banana, 1 medium – 32 mg – 8% DV

Chocolate cravings may be indicative of magnesium deficiency.

Because of the anti-nutrients found in food, processing is actually good in the case of magnesium absorption. For instance, the magnesium in peanut butter is more bioavailable than in peanuts.

By processing, I’m talking more of cooking, soaking, sprouting, and fermenting rather than industrially adding salt.


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