What You Need to Know About Magnesium

There’s a really good chance that you are NOT consuming enough magnesium. (R) It's a crucial mineral that is harder to get in the diet than one might think.



Magnesium is a cofactor for over 300 enzymatic reactions that helps with muscle and nerve function, maintaining blood glucose levels, regulating blood pressure, and energy production. It’s also a critical component in bone health and is needed for DNA, RNA, and glutathione synthesis. If you’re not getting enough magnesium, you will likely be feeling unwell, to say the least. (R)

Magnesium levels are mostly controlled by the kidneys, and about 120 mg of magnesium is excreted into the urine each day. If magnesium levels are low, then urinary excretion will be low. (R)


Testing For Magnesium

Only 1% of the body’s total magnesium is found in the blood. It is difficult to test for magnesium status, since most of the magnesium is found inside cells or in bone. Serum magnesium concentration is often used to assess levels. Other tests, which might be better, are measuring magnesium in red blood cells, saliva, and urine. (R)


Serum Magnesium Levels

  • Normal serum magnesium: 0.75 – 0.95 mmol/L
  • Hypomagnesemia: <0.75 mmol/L


Serum magnesium levels can be normal, but the person might have low whole body magnesium. (R)

Magnesium loading is probably the best test. Magnesium is given intravenously, and magnesium levels are measured in the urine over 24 hours. If deficient, a person will hold on to a lot of the magnesium, and excrete only a little. (R)


Magnesium Deficiency

Symptoms of magnesium deficiency generally show up only when dietary intake of this mineral is low over a long period of time. (R)


Symptoms of Magnesium Deficiency (R)

  • Loss of appetite
  • Nausea
  • Vomiting
  • Fatigue
  • Weakness
  • Numbness
  • Tingling
  • Muscle contractions
  • Cramps
  • Seizures
  • Personality changes
  • Abnormal heart rhythms
  • Coronary spasms
  • Hypocalcemia
  • Hypokalemia


There are different groups of people who are at a greater risk of developing magnesium deficiency, which include people with gastrointestinal disorders and diseases, type 2 diabetes, alcohol dependence, and elderly. (R)


Factors that contribute to Magnesium deficiency (R)

  • Age, as we age, we lose more and absorb less
  • Low dietary intake
  • Water low in magnesium
  • Consuming refined salt, unrefined salt contains magnesium and calcium
  • Pregnancy and lactation
  • Magnesium loss through sweat
  • Consuming alcohol regularly, alcohol is a magnesium diuretic
  • Malabsorption
  • Drugs (i.e. diuretics)


Benefits of Magnesium

Cardiovascular Disease

One meta-analysis found that magnesium supplementation of 243-973 mg/day decreased diastolic blood pressure by only 2.2 mmHg. (R)

Another meta-analysis found that magnesium supplementation decreased systolic blood pressure by 3-4 mmHg and diastolic blood pressure by 2-3 mmHg. (R)

People who have higher levels of serum magnesium (at least 0.88 mmol/L) have a significantly reduced risk of sudden cardiac death compared to those with lower levels of serum magnesium (0.75 mmol/L or less). Higher dietary intakes are also likely to reduce the risk of cardiovascular disease and stroke.


Type 2 Diabetes

Higher dietary intakes of magnesium are associated with a significantly reduced risk of diabetes, and low levels of magnesium may worsen insulin resistance. Insulin resistance and diabetes can also lead to greater losses of magnesium, which creates a viscous cycle, as lower levels of magnesium then worsen blood sugar control.

A meta-analysis found that increasing magnesium intake by 100 mg/day decreases the risk of diabetes by 15%. (R)

Another meta-analysis found that those who consumed higher amounts of dietary magnesium, had a much lower risk of developing type 2 diabetes. (R)

Those with diabetes who supplement with magnesium have been found to have better glucose control, but some studies are mixed. (R)


Bone Health

Magnesium plays a role in bone formation and parathyroid hormone and vitamin D concentrations. Higher intakes of magnesium are associated with better bone health.

Women with osteoporosis have lower serum magnesium levels, and one study found that 290 mg/day of elemental magnesium decreased bone turnover in postmenopausal women with osteoporosis. (R)

Activation of vitamin D is dependent on magnesium. Which is why low magnesium levels in the body can lead to low levels of vitamin D, which then can lead to decreased bone health; among other health concerns. Low calcium causes parathyroid hormone to be excreted. Low magnesium (hypomagnesemia) impairs this response, so parathyroid hormone, calcium and magnesium levels remain low. When magnesium is given, both calcium and parathyroid hormone are restored to normal levels. (R)



People who get migraine headaches have been found to have lower levels of serum and tissue magnesium. A few short-term studies found that supplemental magnesium (up to 600 mg/day) decreased the frequency of headaches only modestly. Some suggest people with migraines take 300 mg of magnesium twice a day to prevent headaches. (R)

However, this dose is higher than the upper limit, so this should only be done under the direction of a healthcare provider.


Alzheimer’s Disease

One study found that persons with Alzheimer’s disease have lower levels of serum total magnesium and serum ionized magnesium compared to people of the same age without Alzheimer’s disease. (R)

A meta-analysis found an association between lower magnesium intakes and an increased risk of stroke. (R)


Calcium Antagonist

Calcium depolarization leads to muscle contraction. Intracellular magnesium helps lower calcium depolarization, which causes increased vascular relaxation. (R)

Magnesium antagonizes calcium and is a natural calcium channel blocker. Calcium causes excitation and contraction, whereas magnesium causes relaxation. (R)


Histamine and Mast Cells

Magnesium appears to play a major role in histamine and mast cells. Magnesium deficient rats were found to have increased mast cells in the small intestine, kidney, bone marrow, and liver. (R)

Another study found that rats fed a magnesium deficient diet had increased levels of histamine. These rats had increased histidine decarboxylase (HDC) activity and low diamine oxidase (DAO) activity. (R) (HDC increases the production of histamine from histidine, and DAO helps degrade histamine.)


Zinc Supplementation

High doses of zinc supplementation (142 mg/day), which is a lot, can decrease the absorption of magnesium and mess with the magnesium balance in the body. (R)


Kidney Function

Impaired kidney function increases the risk of magnesium toxicity, because the kidneys aren’t able to remove the excess magnesium. (R)


Drug Interactions

  • Bisphosphonates - magnesium decreases the absorption of oral bisphosphonates, which are used to treat osteoporosis. (R)
  • Antibiotics – magnesium can form insoluble complexes with certain antibiotics. (R)
  • Loop Diuretics - increase the loss of magnesium in urine, which may lead to lower serum magnesium. (R)
  • Potassium Sparing Diuretics – reduce magnesium excretion, which may lead to higher serum magnesium.(R)
  • Proton Pump Inhibitors – can cause hypomagnesemia if taken for more than one year.(R)
  • Calcitonin - might increase serum magnesium levels. (R)
  • Glucagons – might increase serum magnesium levels. (R)


Magnesium in the Diet

As stated above, most people aren’t consuming adequate amounts of magnesium. It’s a good idea to assess your diet and see if you are consuming enough of this very important mineral.


Recommended Dietary Allowances (RDA) for Magnesium (R)

  • Adult Men: 400-420 mg
  • Adult Women: 310-320 mg


Sources of Magnesium

Good sources of magnesium are nuts, seeds, spinach, kale, legumes, and whole grains. We absorb about 30-40% of dietary magnesium. Daily Value (DV) % is based on 400 mg of magnesium per day. (R)


Top 15 sources of Magnesium (R)

  1. Almonds (1 oz): 80 mg/20%
  2. Spinach, boiled (1/2 cup): 78 mg/20%
  3. Cashews (1 oz): 74 mg/ 19%
  4. Peanuts (1/4 cup): 63 mg/16%
  5. Black beans, cooked (1/2 cup): 60 mg/ 15%
  6. Peanut butter, smooth, (2 tbsp): 49 mg/12%
  7. Bread, whole wheat, (2 slices): 46 mg/12%
  8. Avocado, cubed (1 cup): 44 mg/11%
  9. Potato, baked w/skin (3.5 oz): 43 mg/11%
  10. Brown rice, cooked (1/2 cup): 42 mg/ 11%
  11. Yogurt, plain (8 oz): 42 mg/11%
  12. Oatmeal, instant (1 packet): 36 mg/ 9%
  13. Kidney Beans, canned (1/2 cup): 35 mg/ 9%
  14. Banana (1 medium): 32 mg/9%
  15. Salmon (3 oz): 26 mg/7%


Magnesium Supplements

Magnesium supplements come in many forms, including Magnesium oxide, citrate, chloride, sulfate, glycinate, and malate. Magnesium oxide and sulfate appear to be the least absorbable forms of magnesium. (R)

Taking too much supplemental magnesium will cause a laxative effect. I don’t recommend consuming much supplemental magnesium, and focus more on getting it from food. The supplement should be used only to help meet your daily requirement. Consuming too much magnesium in the form of supplements can cause diarrhea, nausea, and abdominal cramping. Magnesium carbonate, chloride, gluconate, and oxide are the most likely forms to cause issues. (R)


Tolerable Upper Intake Levels (ULs) for Supplemental Magnesium (R)

  • Adult men: 350 mg
  • Adult women: 350 mg


 *As always, please consult your healthcare provider before supplementing or changing your diet.