Magnesium: Are you getting enough?

Magnesium plays a fundamental role in regulating various processes that the body needs to function well. Low levels of magnesium are increasingly linked to disease risk and impaired disease management. Let's answer some frequently asked questions to help you determine how much magnesium you need, the best sources of magnesium and whether you might need a supplement.

Why do we need magnesium and how much should we get each day?

Magnesium is the fourth most abundant mineral, after calcium, sodium and potassium, that the body requires daily. Magnesium is involved in more than 300 enzyme systems necessary for: 

• Creating energy
• Making protein, bone, DNA and RNA
• Muscle contraction (including that of the heart)
• Blood pressure regulation
• Blood sugar control
• Nerve function

The recommended dietary allowance (RDA) of magnesium from all sources (food, beverages, dietary supplements, and medications) for adults is 400-420 milligrams (mg) per day for men and 310-320 mg per day for women.

What specific conditions/symptoms can magnesium help manage?

Research suggests adequate magnesium levels may be effective in reducing the risk of:

• High blood pressure and heart disease
• Insulin resistance and type 2 diabetes
• Osteoporosis
• Migraine headaches
• Alzheimer’s disease, Parkinson’s disease and epilepsy
• Depression and anxiety

Micronutrients vs. macronutrients, and where to find them

Do we generally get enough magnesium from our diets? What if we don’t get enough?

The diets of most Americans don’t give us the recommended amounts of magnesium — especially for teenagers and men 70 and older. People who take magnesium supplements along with with getting magnesium from food typically get enough magnesium to meet or exceed the recommended amount.

Magnesium deficiency is commonly the result of decreased dietary intake, poor absorption and/or increased losses from the body or interactions with medications or other dietary supplements. People who don’t get enough magnesium can experience many different symptoms, from loss of appetite, nausea, mild tremors and generalized weakness to reduced blood flow to the heart and death.

More specific signs and symptoms of magnesium deficiency are outlined below.

Nerve and muscle manifestations:

• Tremors
• Spasms
• Seizures
• Uncontrollable eye movements
• Apathy
• Delirium
• Coma

Heart manifestations:

• Changes in electrical activity of the heart
• Abnormal heart rhythms
• Premature heartbeats
• Heart ischemia (lack of blood flow getting to the heart muscle)

Other electrolyte and hormone abnormalities:

• Low levels of calcium in blood
• Low levels of potassium in blood
• Low levels of parathyroid hormone in blood

What are the most magnesium-rich foods?

Magnesium is widely distributed in foods, occurring in greatest concentrations in nuts, seeds, green leafy vegetables, legumes, whole grain products, soy and chocolate/cocoa. The amount of magnesium found in these foods is influenced by various factors, including: 

• Agricultural practices, like soil and water used for irrigation, fertilizer and conservation 
• Processing techniques like refining and cooking 

Other vegetables, fruits, meat, poultry and fish have moderate amounts of magnesium content, whereas dairy products and beverages have low magnesium content. Foods can also be fortified with magnesium, such as in some breakfast cereals. It can also be found in supplements, either alone or as part of a multivitamin. 

Drinking water sources — bottled mineral and tap — can also contain magnesium and provide portions of the RDA of this mineral, but the amount varies by source and brand, with a range of 1 mg/L to 120 mg/L.

How much magnesium is in specific foods?

• Nuts and seeds
  • Pumpkin seeds, hulled, roasted: 1 ounce = 156 mg 
  • Chia seeds: 1 ounce = 111 mg
  • Almonds, dry roasted: 1 ounce = 80 mg 
  • Cashews, dry roasted: 1 ounce = 74 mg 
  • Peanuts, dry roasted: 1 ounce = 49 mg 
  • Peanut butter, smooth: 2 tablespoons = 49 mg 
  • Flaxseed, whole: 1 tablespoon = 40 mg 
• Greens and other vegetables 
  • Spinach, cooked: ½ cup = 78 mg 
  • Potato, baked with skin: 3.5 ounces = 43 mg 
• Legumes
  • Black beans, cooked: ½ cup = 60 mg
  • Edamame, cooked: ½ cup = 50 mg 
  • Lima beans, cooked: ½ cup = 40 mg 
• Fiber-rich whole grains
  • Quinoa, cooked: ½ cup = 60 mg
  • Cereal, shredded wheat: 2 large biscuits = 61 mg 
  • Rice, brown, cooked: ½ cup = 42-44 mg
  • Wheat germ: 2 tablespoons = 35 mg
  • Bread, whole wheat: 2 slices = 46 mg
• Chocolate
  • Dark chocolate, 70-85% cocoa: 1 ounce = 64 mg
  • Dark chocolate, 60-69% cocoa: 1 ounce = 50 mg
• Low-fat dairy products and soy
  • Soy milk, plain or vanilla: 8 ounces = 61 mg
  • Yogurt, plain or low fat: 8 ounces = 42 mg
  • Milk, nonfat: 8 ounces = 24-27 mg

Source: Magnesium - Health Professional Fact Sheet (nih.gov)

Here’s a link to the U.S. Department of Agriculture’s (USDA’s) Nutrient Database providing a comprehensive list of foods, with magnesium content: https://www.nal.usda.gov/sites/www.nal.usda.gov/files/magnesium.pdf

Who should use a magnesium supplement? What type and dose is best?

Magnesium supplements should be used in addition to your regular diet if you’re unsuccessful in getting enough magnesium from food alone. If you’re eating plenty of food that is typically rich in magnesium, you might still not get enough of the nutrient because nutrient-depleted soil decreased the magnesium content of foods, the magnesium isn’t being absorbed properly in your body, you’re losing excessive amounts of magnesium through urine, you’re dependent on alcohol or interactions with medications or other dietary supplements are keeping your magnesium levels low.

Magnesium supplementation can certainly help fill gaps in a nutrient-deficient diet, but the challenge is discerning which products to use. Talking with your doctor before adding a magnesium supplement to your routine is a good first step. If supplementation is warranted, consider these facts:

• Understand the ideal form and dosage best suited for your individual needs. Magnesium supplements are available in different forms, each with differing absorbability, benefits, and effects on the body. Common forms are glycinate, citrate, chloride, oxide and sulfate. Magnesium citrate is often used to address low levels of magnesium and may also be effective as an acute treatment option for migraine headaches. This form is gentle on the stomach, has good absorbability and is safe.
• Quality seals of certification on supplement product labels assure product integrity (ConsumerLab.com, NSF International, or US Pharmacopeial Convention).
• Medication interactions — magnesium supplements have the potential to interact and decrease the absorption of some medications, both prescription and over-the-counter, including antibiotics, bisphosphonates, diuretics, proton pump inhibitors and high doses of zinc supplementation (142 mg/day). Magnesium supplements can also interact and reduce the effectiveness of antifungals, chemotherapeutic drugs and digitalis.
• Medical contraindications for supplementation — magnesium supplements can cause high amounts of magnesium to build up in the blood in people with chronic kidney disease, leading to muscle weakness.

Are there risks of too much magnesium? What’s considered a high dose? 

The tolerable upper intake level (UL) of magnesium for non-food sources (meaning from dietary supplements and/or medications) is 350 mg per day for adults. High intakes of supplementary magnesium or magnesium-containing medications can be dangerous, even to people without kidney or gastrointestinal disease, and may result in undesirable complications. Common unpleasant side effects are diarrhea, nausea and abdominal cramping. Very high doses of magnesium can cause irregular heart rhythms and cardiac arrest.