Magnesium, an abundant mineral in the body, is naturally present in
many foods, added to other food products, available as a dietary
supplement, and present in some medicines (such as antacids and
laxatives). Magnesium is a cofactor in more than 300 enzyme systems that
regulate diverse biochemical reactions in the body, including protein
synthesis, muscle and nerve function, blood glucose control, and blood
pressure regulation .
Magnesium is required for energy production, oxidative phosphorylation,
and glycolysis. It contributes to the structural development of bone
and is required for the synthesis of DNA, RNA, and the antioxidant
glutathione. Magnesium also plays a role in the active transport of
calcium and potassium ions across cell membranes, a process that is
important to nerve impulse conduction, muscle contraction, and normal
heart rhythm .
An adult body contains approximately 25 g magnesium, with 50% to 60% present in the bones and most of the rest in soft tissues .
Less than 1% of total magnesium is in blood serum, and these levels are
kept under tight control. Normal serum magnesium concentrations range
between 0.75 and 0.95 millimoles (mmol)/L . Hypomagnesemia is defined as a serum magnesium level less than 0.75 mmol/L.
Magnesium homeostasis is largely controlled by the kidney, which
typically excretes about 120 mg magnesium into the urine each day. Urinary excretion is reduced when magnesium status is low .
Assessing magnesium status is difficult because most magnesium is inside cells or in bone.
The most commonly used and readily available method for assessing
magnesium status is measurement of serum magnesium concentration, even
though serum levels have little correlation with total body magnesium
levels or concentrations in specific tissues .
Other methods for assessing magnesium status include measuring
magnesium concentrations in erythrocytes, saliva, and urine; measuring
ionized magnesium concentrations in blood, plasma, or serum; and
conducting a magnesium-loading (or "tolerance") test. No single method
is considered satisfactory. Some experts but not others
consider the tolerance test (in which urinary magnesium is measured
after parenteral infusion of a dose of magnesium) to be the best method
to assess magnesium status in adults. To comprehensively evaluate
magnesium status, both laboratory tests and a clinical assessment might
be required .
Magnesium and Health
Habitually low intakes of magnesium induce changes in biochemical
pathways that can increase the risk of illness over time. This section
focuses on four diseases and disorders in which magnesium might be
involved: hypertension and cardiovascular disease, type 2 diabetes,
osteoporosis, and migraine headaches.
Hypertension and cardiovascular disease
Hypertension is a major risk factor for heart disease and stroke.
Studies to date, however, have found that magnesium supplementation
lowers blood pressure, at best, to only a small extent. A meta-analysis
of 12 clinical trials found that magnesium supplementation for 8–26
weeks in 545 hypertensive participants resulted in only a small
reduction (2.2 mmHg) in diastolic blood pressure .
The dose of magnesium ranged from approximately 243 to 973 mg/day. The
authors of another meta-analysis of 22 studies with 1,173 normotensive
and hypertensive adults concluded that magnesium supplementation for
3–24 weeks decreased systolic blood pressure by 3–4 mmHg and diastolic
blood pressure by 2–3 mmHg.
The effects were somewhat larger when supplemental magnesium intakes of
the participants in the nine crossover-design trials exceeded 370
mg/day. A diet containing more magnesium because of added fruits and
vegetables, more low-fat or non-fat dairy products, and less fat overall
was shown to lower systolic and diastolic blood pressure by an average
of 5.5 and 3.0 mmHg, respectively .
However, this Dietary Approaches to Stop Hypertension (DASH) diet also
increases intakes of other nutrients, such as potassium and calcium,
that are associated with reductions in blood pressure, so any
independent contribution of magnesium cannot be determined.
Several prospective studies have examined associations between
magnesium intakes and heart disease. The Atherosclerosis Risk in
Communities study assessed heart disease risk factors and levels of
serum magnesium in a cohort of 14,232 white and African-American men and
women aged 45 to 64 years at baseline.
Over an average of 12 years of follow-up, individuals in the highest
quartile of the normal physiologic range of serum magnesium (at least
0.88 mmol/L) had a 38% reduced risk of sudden cardiac death compared
with individuals in the lowest quartile (0.75 mmol/L or less). However,
dietary magnesium intakes had no association with risk of sudden cardiac
death. Another prospective study tracked 88,375 female nurses in the
United States to determine whether serum magnesium levels measured early
in the study and magnesium intakes from food and supplements assessed
every 2 to 4 years were associated with sudden cardiac death over 26
years of follow-up .
Women in the highest compared with the lowest quartile of ingested and
plasma magnesium concentrations had a 34% and 77% lower risk of sudden
cardiac death, respectively. Another prospective population study of
7,664 adults aged 20 to 75 years in the Netherlands who did not have
cardiovascular disease found that low urinary magnesium excretion levels
(a marker for low dietary magnesium intake) were associated with a
higher risk of ischemic heart disease over a median follow-up period of
10.5 years. Plasma magnesium concentrations were not associated with
risk of ischemic heart disease .
A systematic review and meta-analysis of prospective studies found that
higher serum levels of magnesium were significantly associated with a
lower risk of cardiovascular disease, and higher dietary magnesium
intakes (up to approximately 250 mg/day) were associated with a
significantly lower risk of ischemic heart disease caused by a reduced
blood supply to the heart muscle .
Higher magnesium intakes might reduce the risk of stroke. In a
meta-analysis of 7 prospective trials with a total of 241,378
participants, an additional 100 mg/day magnesium in the diet was
associated with an 8% decreased risk of total stroke, especially
ischemic rather than hemorrhagic stroke .
One limitation of such observational studies, however, is the
possibility of confounding with other nutrients or dietary components
that could also affect the risk of stroke.
A large, well-designed clinical trial is needed to better understand
the contributions of magnesium from food and dietary supplements to
heart health and the primary prevention of cardiovascular disease .
Type 2 diabetes
Diets with higher amounts of magnesium are associated with a
significantly lower risk of diabetes, possibly because of the important
role of magnesium in glucose metabolism .
Hypomagnesemia might worsen insulin resistance, a condition that often
precedes diabetes, or it might be a consequence of insulin resistance .
Diabetes leads to increased urinary losses of magnesium, and the
subsequent magnesium inadequacy might impair insulin secretion and
action, thereby worsening diabetes control .
Most investigations of magnesium intake and risk of type 2 diabetes
have been prospective cohort studies. A meta-analysis of 7 of these
studies, which included 286,668 patients and 10,912 cases of diabetes
over 6 to 17 years of follow-up, found that a 100 mg/day increase in
total magnesium intake decreased the risk of diabetes by a statistically
significant 15% .
Another meta-analysis of 8 prospective cohort studies that followed
271,869 men and women over 4 to 18 years found a significant inverse
association between magnesium intake from food and risk of type 2
diabetes; the relative risk reduction was 23% when the highest to lowest
intakes were compared .
A 2011 meta-analysis of prospective cohort studies of the association
between magnesium intake and risk of type 2 diabetes included 13
studies with a total of 536,318 participants and 24,516 cases of
diabetes .
The mean length of follow-up ranged from 4 to 20 years. Investigators
found an inverse association between magnesium intake and risk of type 2
diabetes in a dose-responsive fashion, but this association achieved
statistical significance only in overweight (body mass index [BMI] 25 or
higher) but not normal-weight individuals (BMI less than 25). Again, a
limitation of these observational studies is the possibility of
confounding with other dietary components or lifestyle or environmental
variables that are correlated with magnesium intake.
Only a few small, short-term clinical trials have examined the
potential effects of supplemental magnesium on control of type 2
diabetes and the results are conflicting .
For example, 128 patients with poorly controlled diabetes in a
Brazilian clinical trial received a placebo or a supplement containing
either 500 mg/day or 1,000 mg/day magnesium oxide (providing 300 or 600
mg elemental magnesium, respectively) .
After 30 days of supplementation, plasma, cellular, and urine magnesium
levels increased in participants receiving the larger dose of the
supplement, and their glycemic control improved. In another small trial
in Mexico, participants with type 2 diabetes and hypomagnesemia who
received a liquid supplement of magnesium chloride (providing 300 mg/day
elemental magnesium) for 16 weeks showed significant reductions in
fasting glucose and glycosylated hemoglobin concentrations compared with
participants receiving a placebo, and their serum magnesium levels
became normal .
In contrast, neither a supplement of magnesium aspartate (providing 369
mg/day elemental magnesium) nor a placebo taken for 3 months had any
effect on glycemic control in 50 patients with type 2 diabetes who were
taking insulin .
The American Diabetes Association states that there is insufficient
evidence to support the routine use of magnesium to improve glycemic
control in people with diabetes .
It further notes that there is no clear scientific evidence that
vitamin and mineral supplementation benefits people with diabetes who do
not have underlying nutritional deficiencies.
Osteoporosis
Magnesium is involved in bone formation and influences the activities of osteoblasts and osteoclasts .
Magnesium also affects the concentrations of both parathyroid hormone
and the active form of vitamin D, which are major regulators of bone
homeostasis. Several population-based studies have found positive
associations between magnesium intake and bone mineral density in both
men and women .
Other research has found that women with osteoporosis have lower serum
magnesium levels than women with osteopenia and those who do not have
osteoporosis or osteopenia . These and other findings indicate that magnesium deficiency might be a risk factor for osteoporosis .
Although limited in number, studies suggest that increasing magnesium
intakes from food or supplements might increase bone mineral density in
postmenopausal and elderly women .
For example, one short-term study found that 290 mg/day elemental
magnesium (as magnesium citrate) for 30 days in 20 postmenopausal women
with osteoporosis suppressed bone turnover compared with placebo,
suggesting that bone loss decreased .
Diets that provide recommended levels of magnesium enhance bone
health, but further research is needed to elucidate the role of
magnesium in the prevention and management of osteoporosis.
Migraine headaches
Magnesium deficiency is related to factors that promote headaches, including neurotransmitter release and vasoconstriction . People who experience migraine headaches have lower levels of serum and tissue magnesium than those who do not.
However, research on the use of magnesium supplements to prevent or
reduce symptoms of migraine headaches is limited. Three of four small,
short-term, placebo-controlled trials found modest reductions in the
frequency of migraines in patients given up to 600 mg/day magnesium .
The authors of a review on migraine prophylaxis suggested that taking
300 mg magnesium twice a day, either alone or in combination with
medication, can prevent migraines .
In their evidence-based guideline update, the American Academy of
Neurology and the American Headache Society concluded that magnesium
therapy is "probably effective" for migraine prevention.
Because the typical dose of magnesium used for migraine prevention
exceeds the UL, this treatment should be used only under the direction
and supervision of a healthcare provider.
Health Risks from Excessive Magnesium
Too much magnesium from food does not pose a health risk in healthy
individuals because the kidneys eliminate excess amounts in the urine .
However, high doses of magnesium from dietary supplements or
medications often result in diarrhea that can be accompanied by nausea
and abdominal cramping . Forms of magnesium most commonly reported to cause diarrhea include magnesium carbonate, chloride, gluconate, and oxide.
The diarrhea and laxative effects of magnesium salts are due to the
osmotic activity of unabsorbed salts in the intestine and colon and the
stimulation of gastric motility .
Very large doses of magnesium-containing laxatives and antacids
(typically providing more than 5,000 mg/day magnesium) have been
associated with magnesium toxicity , including fatal hypermagnesemia in a 28-month-old boy and an elderly man .
Symptoms of magnesium toxicity, which usually develop after serum
concentrations exceed 1.74–2.61 mmol/L, can include hypotension, nausea,
vomiting, facial flushing, retention of urine, ileus, depression, and
lethargy before progressing to muscle weakness, difficulty breathing,
extreme hypotension, irregular heartbeat, and cardiac arrest .
The risk of magnesium toxicity increases with impaired renal function
or kidney failure because the ability to remove excess magnesium is
reduced or lost .
Magnesium Deficiency
Symptomatic magnesium deficiency due to low dietary intake in
otherwise-healthy people is uncommon because the kidneys limit urinary
excretion of this mineral .
However, habitually low intakes or excessive losses of magnesium due to
certain health conditions, chronic alcoholism, and/or the use of
certain medications can lead to magnesium deficiency.
Early signs of magnesium deficiency include loss of appetite, nausea,
vomiting, fatigue, and weakness. As magnesium deficiency worsens,
numbness, tingling, muscle contractions and cramps, seizures,
personality changes, abnormal heart rhythms, and coronary spasms can
occur .
Severe magnesium deficiency can result in hypocalcemia or hypokalemia
(low serum calcium or potassium levels, respectively) because mineral
homeostasis is disrupted .
Selected Food Sources of Magnesium
| foods |
Milligrams
(mg) per
serving |
Percent
DV* |
|---|
| Almonds, dry roasted, 1 ounce | 80 | 20 |
| Spinach, boiled, ½ cup | 78 | 20 |
| Cashews, dry roasted, 1 ounce | 74 | 19 |
| Peanuts, oil roasted, ¼ cup | 63 | 16 |
| Cereal, shredded wheat, 2 large biscuits | 61 | 15 |
| Soymilk, plain or vanilla, 1 cup | 61 | 15 |
| Black beans, cooked, ½ cup | 60 | 15 |
| Edamame, shelled, cooked, ½ cup | 50 | 13 |
| Peanut butter, smooth, 2 tablespoons | 49 | 12 |
| Bread, whole wheat, 2 slices | 46 | 12 |
| Avocado, cubed, 1 cup | 44 | 11 |
| Potato, baked with skin, 3.5 ounces | 43 | 11 |
| Rice, brown, cooked, ½ cup | 42 | 11 |
| Yogurt, plain, low fat, 8 ounces | 42 | 11 |
| Breakfast cereals, fortified with 10% of the DV for magnesium | 40 | 10 |
| Oatmeal, instant, 1 packet | 36 | 9 |
| Kidney beans, canned, ½ cup | 35 | 9 |
| Banana, 1 medium | 32 | 8 |
| Salmon, Atlantic, farmed, cooked, 3 ounces | 26 | 7 |
| Milk, 1 cup | 24–27 | 6–7 |
| Halibut, cooked, 3 ounces | 24 | 6 |
| Raisins, ½ cup | 23 | 6 |
| Chicken breast, roasted, 3 ounces | 22 | 6 |
| Beef, ground, 90% lean, pan broiled, 3 ounces | 20 | 5 |
| Broccoli, chopped and cooked, ½ cup | 12 | 3 |
| Rice, white, cooked, ½ cup | 10 | 3 |
| Apple, 1 medium | 9 | 2 |
| Carrot, raw, 1 medium | 7 | 2 |
*DV = Daily Value. The DV for magnesium is 400
mg for adults and children aged 4 and older. Foods providing 20% or more of the DV are
considered to be high sources of a nutrient.
Recommended Dietary Allowances (RDAs) for Magnesium
| Age |
Male |
Female |
Pregnancy |
Lactation |
|---|
| Birth to 6 months | 30 mg* | 30 mg* | | |
| 7–12 months | 75 mg* | 75 mg* | | |
| 1–3 years | 80 mg | 80 mg | | |
| 4–8 years | 130 mg | 130 mg | | |
| 9–13 years | 240 mg | 240 mg | | |
| 14–18 years | 410 mg | 360 mg | 400 mg | 360 mg |
| 19–30 years | 400 mg | 310 mg | 350 mg | 310 mg |
| 31–50 years | 420 mg | 320 mg | 360 mg | 320 mg |
| 51+ years | 420 mg | 320 mg | | |
*Adequate Intake (AI)
ps- note that there are risks by taking excessive of magnesium, so kindly consult your doctor before taking any steps.
THIS IS ONLY FOR INFORMATION, ALWAYS CONSULT YOU PHYSICIAN BEFORE
HAVING ANY PARTICULAR FOOD/ MEDICATION/EXERCISE/OTHER REMEDIES.
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