Magnesium
macro-mineral
Key Takeaways
- Magnesium is a cofactor in more than 300 enzyme systems regulating protein synthesis, muscle/nerve function, blood glucose, and blood pressure
- FDA daily value is 420 mg; adult men need 400-420 mg/day, women need 310-320 mg/day
- 50-60% of body magnesium is stored in bones; less than 1% is in blood serum
- Habitually low intakes are common, especially in older adults and those consuming processed foods
- Organic forms (citrate, glycinate) appear more bioavailable than inorganic forms (oxide, sulfate) (pmid:34111673)
Evidence Spectrum
15 studies reviewed →Blood pressure and cardiovascular health
Multiple epidemiological and clinical studies confirm a close relationship between magnesium deficit and high blood pressure. Magnesium contributes to regulation of cardiac excitation-contraction coupling, endothelial functioning, and hemostasis. A 2021 review noted that evidence supports a protective effect against hypertension and its complications, particularly in older adults who are more frequently at risk of magnesium deficiency.56
Prevention and therapy of chronic diseases
Low magnesium levels have been associated with Alzheimer's disease, insulin resistance and type-2 diabetes, hypertension, cardiovascular disease (including stroke), migraine headaches, and ADHD. Magnesium plays important roles in prevention and treatment of many diseases through its involvement in ATP metabolism and numerous enzymatic reactions.1
Skeletal health
Magnesium appears to be involved in bone metabolism and deficiency could negatively influence bone and muscle health. However, a 2020 review found that data regarding the efficacy of magnesium supplementation on bone outcomes remain inconclusive.2
Energy, fatigue, and cognition
Magnesium's involvement in energy-yielding metabolism, DNA synthesis, oxygen transport, and neuronal functions makes it critical for brain and muscular function. Magnesium deprivation increases oxygen requirements for submaximal exercise and reduces endurance performance.3
Physical performance in older adults
Magnesium supplementation appears to demonstrate a potential association with physical activity and muscle performance in older individuals, possibly relevant to sarcopenia prevention. However, data remain limited.4
15
Studies Reviewed
30 mg
RDA (Infants 0-6 months (AI))
350 mg
Upper Limit
Role in the Body
Magnesium is the fourth most abundant mineral in the body, serving as a cofactor in more than 300 enzyme systems that regulate diverse biochemical reactions. These include protein synthesis, muscle and nerve function, blood glucose control, and blood pressure regulation. Magnesium is required for energy production through oxidative phosphorylation and glycolysis, and contributes to the structural development of bone. Magnesium is also required for the synthesis of DNA, RNA, and the antioxidant glutathione. It plays a critical role in the active transport of calcium and potassium ions across cell membranes, a process important to nerve impulse conduction, muscle contraction, and normal heart rhythm. An adult body contains approximately 25 grams of magnesium, with 50-60% present in bones and most of the rest in soft tissues. Less than 1% of total magnesium is in blood serum (normal range: 0.75-0.95 mmol/L). Hypomagnesemia is defined as serum magnesium below 0.75 mmol/L. Magnesium homeostasis is largely controlled by the kidneys, which typically excrete about 120 mg/day into urine, with excretion reduced when status is low.
- Cofactor for 300+ enzyme systems
- Energy production (ATP metabolism, oxidative phosphorylation, glycolysis)
- Protein synthesis
- Muscle and nerve function
- Blood glucose control
- Blood pressure regulation
- Structural development of bone
- DNA and RNA synthesis
- Glutathione synthesis (antioxidant defense)
- Active transport of calcium and potassium across cell membranes
- Normal heart rhythm maintenance
Supplement Forms
Magnesium citrate
RecommendedBioavailability: 25%
Organic form with higher bioavailability than inorganic forms. Well-absorbed. May have mild laxative effect at higher doses.
Magnesium glycinate (bisglycinate)
RecommendedBioavailability: 24%
Chelated organic form. Well-tolerated with minimal GI side effects. Good option for those seeking to avoid laxative effects.
Magnesium oxide
Bioavailability: 4%
Inorganic form with low bioavailability despite high elemental magnesium content (60%). Commonly used but poorly absorbed. More suitable as a laxative than a supplement.
Magnesium chloride
RecommendedBioavailability: 20%
Inorganic form with reasonable bioavailability. Available in topical and oral forms.
Magnesium taurate
RecommendedBioavailability: 15%
Combined with taurine. Often marketed for cardiovascular support, though specific clinical evidence is limited.
Magnesium L-threonate
Bioavailability: 15%
Marketed for brain health and cognitive function. Limited clinical evidence compared to other forms. More expensive.
Food Sources
Pumpkin seeds
550 mg per 100g
Almonds
270 mg per 100g
Spinach (cooked)
87 mg per 100g
Dark chocolate (70-85% cacao)
228 mg per 100g
Black beans (cooked)
70 mg per 100g
Avocado
29 mg per 100g
Tofu, firm (with calcium sulfate and magnesium chloride)
37 mg per 100g
Whole grains
varies; good dietary source
Nuts and legumes
varies; optimal dietary sources recommended for hypertension prevention (pmid:33396570)
Deficiency
Prevalence: Symptomatic deficiency due to low dietary intake alone is uncommon in healthy people because the kidneys limit urinary excretion. However, habitually low intakes are widespread, particularly among those consuming processed foods. Older adults are more frequently at risk of deficiency through multiple mechanisms.
Symptoms:
- Early: loss of appetite, nausea, vomiting, fatigue, weakness
- Progressive: numbness, tingling, muscle contractions and cramps, seizures
- Severe: personality changes, abnormal heart rhythms, coronary spasms
- Severe deficiency can cause hypocalcemia (low calcium) or hypokalemia (low potassium)
Risk Factors:
- Chronic alcoholism
- Type 2 diabetes and insulin resistance
- Gastrointestinal diseases (Crohn's disease, celiac disease)
- Older adults
- People taking certain medications (proton pump inhibitors, diuretics)
- High consumption of processed foods (very poor in magnesium)
- Chronic kidney disease
Safety & Interactions
Possible Side Effects:
- • Diarrhea and GI discomfort (most common, especially with magnesium oxide and citrate at high doses)
- • Nausea at high supplemental doses
- • Hypermagnesemia is rare in people with normal kidney function
Drug Interactions:
- • Calcium: magnesium is required for proper calcium metabolism; deficiency can cause hypocalcemia
- • Vitamin D: magnesium is needed for vitamin D metabolism
- • Bisphosphonates: magnesium can reduce absorption; separate by 2+ hours
- • Antibiotics (tetracyclines, quinolones): magnesium can reduce absorption; separate doses
- • Diuretics: loop and thiazide diuretics can increase magnesium excretion
Contraindications:
- • Severe renal insufficiency (kidneys cannot excrete excess magnesium)
- • Myasthenia gravis (magnesium can worsen muscle weakness)
- • Heart block (without pacemaker)
Frequently Asked Questions
How much magnesium should I take daily?
The FDA daily value is 420 mg. Adult men need 400-420 mg/day and women need 310-320 mg/day from food and supplements combined. Supplemental magnesium should not exceed 350 mg/day (the UL applies to supplements only, not dietary magnesium).
Which form of magnesium is best absorbed?
Research shows organic forms (citrate, glycinate, chloride) are generally more bioavailable than inorganic forms (oxide, sulfate). Magnesium oxide, despite having the highest elemental magnesium content, has the lowest absorption rate at roughly 4%. Magnesium citrate and glycinate are commonly recommended.
What are the symptoms of magnesium deficiency?
Early signs include loss of appetite, nausea, fatigue, and weakness. As deficiency progresses, symptoms can include numbness, tingling, muscle cramps, seizures, abnormal heart rhythms, and personality changes. Severe deficiency can also cause low calcium and potassium levels.
Does magnesium help with blood pressure?
Multiple studies show a relationship between magnesium deficit and high blood pressure. Magnesium supports cardiovascular function through regulation of vascular tone, cardiac rhythm, and endothelial function. Increasing intake of magnesium-rich foods (vegetables, nuts, whole grains, legumes) is recommended for hypertension prevention.
Research Sources
15 peer-reviewed studies analyzed from PubMed. 6 directly cited in this review.