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Magnesium

Office of Dietary Supplements • National Institutes of Health
Table of Contents

Magnesium: What is it?
What foods provide magnesium?
What are the Dietary Reference Intakes for magnesium?
When can magnesium deficiency occur?
Who may need extra magnesium?
What is the best way to get extra magnesium?
What are some current issues and controversies about magnesium?
What is the health risk of too much magnesium?
Selecting a healthful diet
References
Magnesium: What is it?

Magnesium is the fourth most abundant mineral in the body and is
essential to good health. Approximately 50% of total body magnesium is
found in bone. The other half is found predominantly inside cells of
body tissues and organs. Only 1% of magnesium is found in blood, but
the body works very hard to keep blood levels of magnesium constant 1.
Magnesium is needed for more than 300 biochemical reactions in the
body. It helps maintain normal muscle and nerve function, keeps heart
rhythm steady, supports a healthy immune system, and keeps bones
strong. Magnesium also helps regulate blood sugar levels, promotes
normal blood pressure, and is known to be involved in energy
metabolism and protein synthesis 2-3. There is an increased interest
in the role of magnesium in preventing and managing disorders such as
hypertension, cardiovascular disease, and diabetes. Dietary magnesium
is absorbed in the small intestines. Magnesium is excreted through the
kidneys 1-3,4.

What foods provide magnesium?
Green vegetables such as spinach are good sources of magnesium because
the center of the chlorophyll molecule (which gives green vegetables
their color) contains magnesium. Some legumes (beans and peas), nuts
and seeds, and whole, unrefined grains are also good sources of
magnesium 5. Refined grains are generally low in magnesium 4-5.
When white flour is refined and processed, the magnesium-rich germ and
bran are removed. Bread made from whole grain wheat flour provides
more magnesium than bread made from white refined flour. Tap water can
be a source of magnesium, but the amount varies according to the water
supply. Water that naturally contains more minerals is described as
"hard". "Hard" water contains more magnesium than "soft" water.

Eating a wide variety of legumes, nuts, whole grains, and vegetables
will help you meet your daily dietary need for magnesium. Selected
food sources of magnesium are listed in Table 1.
Table 1: Selected food sources of magnesium 5

FOOD
Milligrams (mg)

%DV
Halibut, cooked, 3 ounces

90
20

Almonds, dry roasted, 1 ounce
80

20
Cashews, dry roasted, 1 ounce

75
20

Soybeans, mature, cooked, ½ cup
75

20
Spinach, frozen, cooked, ½ cup

75
20

Nuts, mixed, dry roasted, 1 ounce
65

15
Cereal, shredded wheat, 2 rectangular biscuits

55
15

Oatmeal, instant, fortified, prepared w/ water, 1 cup
55

15
Potato, baked w/ skin, 1 medium

50
15

Peanuts, dry roasted, 1 ounce
50

15
Peanut butter, smooth, 2 Tablespoons

50
15

Wheat Bran, crude, 2 Tablespoons
45

10
Blackeyed Peas, cooked, ½ cup

45
10

Yogurt, plain, skim milk, 8 fluid ounces
45

10
Bran Flakes, ½ cup

40
10

Vegetarian Baked Beans, ½ cup
40

10
Rice, brown, long-grained, cooked, ½ cup

40
10

Lentils, mature seeds, cooked, ½ cup
35

8
Avocado, California, ½ cup pureed

35
8

Kidney Beans, canned, ½ cup
35

8
Pinto Beans, cooked, ½ cup

35
8

Wheat Germ, crude, 2 Tablespoons
35

8
Chocolate milk, 1 cup

33
8

Banana, raw, 1 medium
30

8
Milk Chocolate candy bar, 1.5 ounce bar

28
8

Milk, reduced fat (2%) or fat free, 1 cup
27

8
Bread, whole wheat, commercially prepared, 1 slice

25
6

Raisins, seedless, ½ cup packed
25

6
Whole Milk, 1 cup

24
6

Chocolate Pudding, 4 ounce ready-to-eat portion
24

6
DV = Daily Value. DVs are reference numbers developed by the Food and
Drug Administration (FDA) to help consumers determine if a food
contains a lot or a little of a specific nutrient. The DV for
magnesium is 400 milligrams (mg). Most food labels do not list a
food's magnesium content. The percent DV (%DV) listed on the table
above indicates the percentage of the DV provided in one serving. A
food providing 5% of the DV or less per serving is a low source while
a food that provides 10-19% of the DV is a good source. A food that
provides 20% or more of the DV is high in that nutrient. It is
important to remember that foods that provide lower percentages of the
DV also contribute to a healthful diet. For foods not listed in this
table, please refer to the U.S. Department of Agriculture's Nutrient
Database Web site: http://www.nal.usda.gov/fnic/cgi-bin/nutsearch.pl.

What are the Dietary Reference Intakes for magnesium?
Recommendations for magnesium are provided in the Dietary Reference
Intakes (DRIs) developed by the Institute of Medicine of the National
Academy of Sciences 4. Dietary Reference Intakes is the general term
for a set of reference values used for planning and assessing nutrient
intake for healthy people. Three important types of reference values
included in the DRIs are Recommended Dietary Allowances (RDA),
Adequate Intakes (AI), and Tolerable Upper Intake Levels (UL). The RDA
recommends the average daily intake that is sufficient to meet the
nutrient requirements of nearly all (97%-98%) healthy people. An AI is
set when there is insufficient scientific data available to establish
a RDA for specific age/gender groups. AIs meet or exceed the amount
needed to maintain a nutritional state of adequacy in nearly all
members of a specific age and gender group. The UL, on the other hand,
is the maximum daily intake unlikely to result in adverse health
effects. Table 2 lists the RDAs for magnesium, in milligrams, for
children and adults 4.

Table 2: Recommended Dietary Allowances for magnesium for children and
adults 4
Age
(years)

Male
(mg/day)
Female
(mg/day)

Pregnancy
(mg/day)
Lactation
(mg/day)

1-3
80

80
N/A

N/A
4-8

130
130

N/A
N/A

9-13
240

240
N/A

N/A
14-18

410
360

400
360

19-30
400

310
350

310
31+

420
320

360
320

There is insufficient information on magnesium to establish a RDA for
infants. For infants 0 to 12 months, the DRI is in the form of an
Adequate Intake (AI), which is the mean intake of magnesium in
healthy, breastfed infants. Table 3 lists the AIs for infants in
milligrams (mg) 4.
Table 3: Recommended Adequate Intake for magnesium for infants 4

Age
(months)
Males and Females
(mg/day)
  1. to 6
30
  1. to 12
75

Data from the 1999-2000 National Health and Nutrition Examination
Survey suggest that substantial numbers of adults in the United States
(US) fail to get recommended amounts of magnesium in their diets.
Among adult men and women, the diets of Caucasians have significantly
more magnesium than do those of African-Americans. Magnesium intake is
lower among older adults in every racial and ethnic group. Among
African-American men and Caucasian men and women who take dietary
supplements, the intake of magnesium is significantly higher than in
those who do not 6.
When can magnesium deficiency occur?

Even though dietary surveys suggest that many Americans do not get
recommended amounts of magnesium, symptoms of magnesium deficiency are
rarely seen in the US. However, there is concern that many people may
not have enough body stores of magnesium because dietary intake may
not be high enough. Having enough body stores of magnesium may be
protective against disorders such as cardiovascular disease and immune
dysfunction 7-8.
The health status of the digestive system and the kidneys
significantly influence magnesium status. Magnesium is absorbed in the
intestines and then transported through the blood to cells and
tissues. Approximately one-third to one-half of dietary magnesium is
absorbed into the body 9-10. Gastrointestinal disorders that impair
absorption such as Crohn's disease can limit the body's ability to
absorb magnesium. These disorders can deplete the body's stores of
magnesium and in extreme cases may result in magnesium deficiency.
Chronic or excessive vomiting and diarrhea may also result in
magnesium depletion 1,10.

Healthy kidneys are able to limit urinary excretion of magnesium to
make up for low dietary intake. However, excessive loss of magnesium
in urine can be a side effect of some medications and can also occur
in cases of poorly-controlled diabetes and alcohol abuse 11-18.
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 (sudden
changes in behaviors caused by excessive electrical activity in the
brain), personality changes, abnormal heart rhythms, and coronary
spasms can occur 1,3-4. Severe magnesium deficiency can result in
low levels of calcium in the blood (hypocalcemia). Magnesium
deficiency is also associated with low levels of potassium in the
blood (hypokalemia) 1,19-20.

Many of these symptoms are general and can result from a variety of
medical conditions other than magnesium deficiency. It is important to
have a physician evaluate health complaints and problems so that
appropriate care can be given.
Who may need extra magnesium?

Magnesium supplementation may be indicated when a specific health
problem or condition causes an excessive loss of magnesium or limits
magnesium absorption 2,7,9-11.
Some medicines may result in magnesium deficiency, including
 certain diuretics, antibiotics, and medications used to treat
 cancer (anti-neoplastic medication) 12,14,19. Examples of these
 medications are:

Diuretics: Lasix, Bumex, Edecrin, and hydrochlorothiazide
Antibiotics: Gentamicin, and Amphotericin

Anti-neoplastic medication: Cisplatin
Individuals with poorly-controlled diabetes may benefit from
 magnesium supplements because of increased magnesium loss in urine
 associated with hyperglycemia 21.

Magnesium supplementation may be indicated for persons with
 alcoholism. Low blood levels of magnesium occur in 30% to 60% of
 alcoholics, and in nearly 90% of patients experiencing alcohol
 withdrawal 17-18. Anyone who substitutes alcohol for food will
 usually have significantly lower magnesium intakes.
Individuals with chronic malabsorptive problems such as Crohn's
 disease, gluten sensitive enteropathy, regional enteritis, and
 intestinal surgery may lose magnesium through diarrhea and fat
 malabsorption 22. Individuals with these conditions may need
 supplemental magnesium.

Individuals with chronically low blood levels of potassium and
 calcium may have an underlying problem with magnesium deficiency.
 Magnesium supplements may help correct the potassium and calcium
 deficiencies 19.
Older adults are at increased risk for magnesium deficiency. The
 1999-2000 and 1998-94 National Health and Nutrition Examination
 Surveys suggest that older adults have lower dietary intakes of
 magnesium than younger adults 6,23. In addition, magnesium
 absorption decreases and renal excretion of magnesium increases in
 older adults 4. Seniors are also more likely to be taking drugs
 that interact with magnesium. This combination of factors places
 older adults at risk for magnesium deficiency 4. It is very
 important for older adults to get recommended amounts of dietary
 magnesium.

Doctors can evaluate magnesium status when above-mentioned medical
problems occur, and determine the need for magnesium supplementation.
Table 4 describes some important interactions between certain drugs
and magnesium. These interactions may result in higher or lower levels
of magnesium, or may influence absorption of the medication.

Table 4: Common and important magnesium/drug interactions
Drug

Potential Interaction
Loop and thiazide diuretics (e.g. lasix, bumex, edecrin, and
 hydrochlorthiazide

Anti-neoplastic drugs (e.g. cisplatin)
Antibiotics (e.g. gentamicin and amphotericin)

These drugs may increase the loss of magnesium in urine. Thus, taking
these medications for long periods of time may contribute to magnesium
depletion 9-10,12.
Tetracycline antibiotics

Magnesium binds tetracycline in the gut and decreases the absorption
of tetracycline 24.
Magnesium-containing antacids and laxatives

Many antacids and laxatives contain magnesium. When frequently taken
in large doses, these drugs can inadvertently lead to excessive
magnesium consumption 25-26 and hypermagnesemia, which refers to
elevated levels of magnesium in blood.
What is the best way to get extra magnesium?

Eating a variety of whole grains, legumes, and vegetables (especially
dark-green, leafy vegetables) every day will help provide recommended
intakes of magnesium and maintain normal storage levels of this
mineral. Increasing dietary intake of magnesium can often restore
mildly depleted magnesium levels. However, increasing dietary intake
of magnesium may not be enough to restore very low magnesium levels to
normal.
When blood levels of magnesium are very low, intravenous (i.e. by IV)
magnesium replacement is usually recommended. Magnesium tablets also
may be prescribed, although some forms can cause diarrhea 27. It is
important to have the cause, severity, and consequences of low blood
levels of magnesium evaluated by a physician, who can recommend the
best way to restore magnesium levels to normal. Because people with
kidney disease may not be able to excrete excess amounts of magnesium,
they should not take magnesium supplements unless prescribed by a
physician.

Oral magnesium supplements combine magnesium with another substance
such as a salt. Examples of magnesium supplements include magnesium
oxide, magnesium sulfate, and magnesium carbonate. Elemental magnesium
refers to the amount of magnesium in each compound. Figure 1 compares
the amount of elemental magnesium in different types of magnesium
supplements 28. The amount of elemental magnesium in a compound and
its bioavailability influence the effectiveness of the magnesium
supplement. Bioavailability refers to the amount of magnesium in food,
medications, and supplements that is absorbed in the intestines and
ultimately available for biological activity in your cells and
tissues. Enteric coating (the outer layer of a tablet or capsule that
allows it to pass through the stomach and be dissolved in the small
intestine) of a magnesium compound can decrease bioavailability 29.
In a study that compared four forms of magnesium preparations, results
suggested lower bioavailability of magnesium oxide, with significantly
higher and equal absorption and bioavailability of magnesium chloride
and magnesium lactate 30. This supports the belief that both the
magnesium content of a dietary supplement and its bioavailability
contribute to its ability to restore deficient levels of magnesium.
Percent Magnesium content of oral supplements
The information in Figure 1 is provided to demonstrate the variable
amount of magnesium in magnesium supplements.
What are some current issues and controversies about magnesium?

Magnesium and blood pressure
"Epidemiologic evidence suggests that magnesium may play an important
role in regulating blood pressure 4." Diets that provide plenty of
fruits and vegetables, which are good sources of potassium and
magnesium, are consistently associated with lower blood pressure 31-33.
The DASH study (Dietary Approaches to Stop Hypertension), a human
clinical trial, suggested that high blood pressure could be
significantly lowered by a diet that emphasizes fruits, vegetables,
and low fat dairy foods. Such a diet will be high in magnesium,
potassium, and calcium, and low in sodium and fat 34-36.
An observational study examined the effect of various nutritional
factors on incidence of high blood pressure in over 30,000 US male
health professionals. After four years of follow-up, it was found that
a lower risk of hypertension was associated with dietary patterns that
provided more magnesium, potassium, and dietary fiber 37. For 6
years, the Atherosclerosis Risk in Communities (ARIC) Study followed
approximately 8,000 men and women who were initially free of
hypertension. In this study, the risk of developing hypertension
decreased as dietary magnesium intake increased in women, but not in
men 38.

Foods high in magnesium are frequently high in potassium and dietary
fiber. This makes it difficult to evaluate the independent effect of
magnesium on blood pressure. However, newer scientific evidence from
DASH clinical trials is strong enough that the Joint National
Committee on Prevention, Detection, Evaluation, and Treatment of High
Blood Pressure states that diets that provide plenty of magnesium are
positive lifestyle modifications for individuals with hypertension.
This group recommends the DASH diet as a beneficial eating plan for
people with hypertension and for those with "prehypertension" who
desire to prevent high blood pressure
http://www.nhlbi.nih.gov/health/public/heart/hbp/dash/ 39-41.
Magnesium and diabetes
Diabetes is a disease resulting in insufficient production and/or
inefficient use of insulin. Insulin is a hormone made by the pancreas.
Insulin helps convert sugar and starches in food into energy to
sustain life. There are two types of diabetes: type 1 and type 2. Type
1 diabetes is most often diagnosed in children and adolescents, and
results from the body's inability to make insulin. Type 2 diabetes,
which is sometimes referred to as adult-onset diabetes, is the most
common form of diabetes. It is usually seen in adults and is most
often associated with an inability to use the insulin made by the
pancreas. Obesity is a risk factor for developing type 2 diabetes. In
recent years, rates of type 2 diabetes have increased along with the
rising rates of obesity.

Magnesium plays an important role in carbohydrate metabolism. It may
influence the release and activity of insulin, the hormone that helps
control blood glucose (sugar) levels 13. Low blood levels of
magnesium (hypomagnesemia) are frequently seen in individuals with
type 2 diabetes. Hypomagnesemia may worsen insulin resistance, a
condition that often precedes diabetes, or may be a consequence of
insulin resistance. Individuals with insulin resistance do not use
insulin efficiently and require greater amounts of insulin to maintain
blood sugar within normal levels. The kidneys possibly lose their
ability to retain magnesium during periods of severe hyperglycemia
(significantly elevated blood glucose). The increased loss of
magnesium in urine may then result in lower blood levels of magnesium
4. In older adults, correcting magnesium depletion may improve
insulin response and action 42.
The Nurses' Health Study (NHS) and the Health Professionals' Follow-up
Study (HFS) follow more than 170,000 health professionals through
questionnaires the participants complete every 2 years. Diet was first
evaluated in 1980 in the NHS and in 1986 in the HFS, and dietary
assessments have been completed every 2 to 4 years since. Information
on the use of dietary supplements, including multivitamins, is also
collected. As part of these studies, over 127,000 participants (85,060
women and 42,872 men) with no history of diabetes, cardiovascular
disease, or cancer at baseline were followed to examine risk factors
for developing type 2 diabetes. Women were followed for 18 years; men
were followed for 12 years. Over time, the risk for developing type 2
diabetes was greater in men and women with a lower magnesium intake.
This study supports the dietary recommendation to increase consumption
of major food sources of magnesium, such as whole grains, nuts, and
green leafy vegetables 43.

The Iowa Women's Health Study has followed a group of older women
since 1986. Researchers from this study examined the association
between women's risk of developing type 2 diabetes and intake of
carbohydrates, dietary fiber, and dietary magnesium. Dietary intake
was estimated by a food frequency questionnaire, and incidence of
diabetes throughout 6 years of follow-up was determined by asking
participants if they had been diagnosed by a doctor as having
diabetes. Based on baseline dietary intake assessment only,
researchers' findings suggested that a greater intake of whole grains,
dietary fiber, and magnesium decreased the risk of developing diabetes
in older women 44.
The Women's Health Study was originally designed to evaluate the
benefits versus risks of low-dose aspirin and vitamin E
supplementation in the primary prevention of cardiovascular disease
and cancer in women 45 years of age and older. In an examination of
almost 40,000 women participating in this study, researchers also
examined the association between magnesium intake and incidence of
type 2 diabetes over an average of 6 years. Among women who were
overweight, the risk of developing type 2 diabetes was significantly
greater among those with lower magnesium intake 45. This study also
supports the dietary recommendation to increase consumption of major
food sources of magnesium, such as whole grains, nuts, and green leafy
vegetables.

On the other hand, the Atherosclerosis Risk in Communities (ARIC)
study did not find any association between dietary magnesium intake
and the risk for type 2 diabetes. During 6 years of follow-up, ARIC
researchers examined the risk for type 2 diabetes in over 12,000
middle-aged adults without diabetes at baseline examination. In this
study, there was no association between dietary magnesium intake and
incidence of type 2 diabetes in either black or white participants 46.
It can be confusing to read about studies that examine the same issue
but have different results. Before reaching a conclusion on a health
issue, scientists conduct and evaluate many studies. Over time, they
determine when results are consistent enough to suggest a conclusion.
They want to be sure they are providing correct recommendations to the
public.
Several clinical studies have examined the potential benefit of
supplemental magnesium on control of type 2 diabetes. In one such
study, 63 subjects with below normal serum magnesium levels received
either 2.5 grams of oral magnesium chloride daily "in liquid form"
(providing 300 mg elemental magnesium per day) or a placebo. At the
end of the 16-week study period, those who received the magnesium
supplement had higher blood levels of magnesium and improved control
of diabetes, as suggested by lower hemoglobin A1C levels, than those
who received a placebo 47. Hemoglobin A1C is a test that measures
overall control of blood glucose over the previous 2 to 3 months, and
is considered by many doctors to be the single most important blood
test for diabetics.

In another study, 128 patients with poorly controlled type 2 diabetes
were randomized to receive a placebo or a supplement with either 500
mg or 1000 mg of magnesium oxide (MgO) for 30 days. All patients were
also treated with diet or diet plus oral medication to control blood
glucose levels. Magnesium levels increased in the group receiving 1000
mg magnesium oxide per day (equal to 600 mg elemental magnesium per
day) but did not significantly change in the placebo group or the
group receiving 500 mg of magnesium oxide per day (equal to 300 mg
elemental magnesium per day). However, neither level of magnesium
supplementation significantly improved blood glucose control 48.
These studies provide intriguing results but also suggest that
additional research is needed to better explain the association
between blood magnesium levels, dietary magnesium intake, and type 2
diabetes. In 1999, the American Diabetes Association (ADA) issued
nutrition recommendations for diabetics stating that "routine
evaluation of blood magnesium level is recommended only in patients at
high risk for magnesium deficiency. Levels of magnesium should be replaced
only if hypomagnesemia can be demonstrated" 21.

Magnesium and cardiovascular disease
Magnesium metabolism is very important to insulin sensitivity and
blood pressure regulation, and magnesium deficiency is common in
individuals with diabetes. The observed associations between magnesium
metabolism, diabetes, and high blood pressure increase the likelihood
that magnesium metabolism may influence cardiovascular disease 49.
Some observational surveys have associated higher blood levels of
magnesium with lower risk of coronary heart disease 50-51. In
addition, some dietary surveys have suggested that a higher magnesium
intake may reduce the risk of having a stroke 52. There is also
evidence that low body stores of magnesium increase the risk of
abnormal heart rhythms, which may increase the risk of complications
after a heart attack 4. These studies suggest that consuming
recommended amounts of magnesium may be beneficial to the
cardiovascular system. They have also prompted interest in clinical
trials to determine the effect of magnesium supplements on
cardiovascular disease.

Several small studies suggest that magnesium supplementation may
improve clinical outcomes in individuals with coronary disease. In one
of these studies, the effect of magnesium supplementation on exercise
tolerance (the ability to walk on a treadmill or ride a bicycle),
chest pain caused by exercise, and quality of life was examined in 187
patients. Patients received either a placebo or a supplement providing
365 milligrams of magnesium citrate twice daily for 6 months. At the
end of the study period researchers found that magnesium therapy
significantly increased magnesium levels. Patients receiving magnesium
had a 14 percent improvement in exercise duration as compared to no
change in the placebo group. Those receiving magnesium were also less
likely to experience chest pain caused by exercise 53.
In another study, 50 men and women with stable coronary disease were
randomized to receive either a placebo or a magnesium supplement that
provided 342 mg magnesium oxide twice daily. After 6 months, those who
received the oral magnesium supplement were found to have improved
exercise tolerance 54.

In a third study, researchers examined whether magnesium
supplementation would add to the anti-thrombotic (anti-clotting)
effects of aspirin in 42 coronary patients 55. For three months,
each patient received either a placebo or a supplement with 400 mg of
magnesium oxide two to three times daily. After a four-week break
without any treatment, treatment groups were reversed so that each
person in the study then received the alternate treatment for three
months. Researchers found that supplemental magnesium did provide an
additional anti-thrombotic effect.
These studies are encouraging, but involved small numbers. Additional
studies are needed to better understand the complex relationships
between magnesium intake, indicators of magnesium status, and heart
disease. Doctors can evaluate magnesium status when above-mentioned
medical problems occur, and determine the need for magnesium
supplementation.

Magnesium and osteoporosis
Bone health is supported by many factors, most notably calcium and
vitamin D. However, some evidence suggests that magnesium deficiency
may be an additional risk factor for postmenopausal osteoporosis 4.
This may be due to the fact that magnesium deficiency alters calcium
metabolism and the hormones that regulate calcium (20). Several human
studies have suggested that magnesium supplementation may improve bone
mineral density 4. In a study of older adults, a greater magnesium
intake maintained bone mineral density to a greater degree than a
lower magnesium intake 56. Diets that provide recommended levels of
magnesium are beneficial for bone health, but further investigation on
the role of magnesium in bone metabolism and osteoporosis is needed.
What is the health risk of too much magnesium?

Dietary magnesium does not pose a health risk, however pharmacologic
doses of magnesium in supplements can promote adverse effects such as
diarrhea and abdominal cramping. Risk of magnesium toxicity increases
with kidney failure, when the kidney loses the ability to remove
excess magnesium. Very large doses of magnesium-containing laxatives
and antacids also have been associated with magnesium toxicity 25.
For example, a case of hypermagnesemia after unsupervised intake of
aluminum magnesia oral suspension occurred after a 16 year old girl
decided to take the antacid every two hours rather than four times per
day, as prescribed. Three days later, she became unresponsive and
demonstrated loss of deep tendon reflex 57. Doctors were unable to
determine her exact magnesium intake, but the young lady presented
with blood levels of magnesium five times higher than normal 25.
Therefore, it is important for medical professionals to be aware of
the use of any magnesium-containing laxatives or antacids. Signs of
excess magnesium can be similar to magnesium deficiency and include
changes in mental status, nausea, diarrhea, appetite loss, muscle
weakness, difficulty breathing, extremely low blood pressure, and
irregular heartbeat 5,57-60.
Table 5 lists the ULs for supplemental magnesium for healthy infants,
children, and adults in milligrams (mg) 4. Physicians may prescribe
magnesium in higher doses for specific medical problems. There is no
UL for dietary intake of magnesium; only for magnesium supplements.

Table 5: Tolerable Upper Intake Levels for supplemental magnesium for
children and adults 4
Age (years)

Male
(mg/day)
Female
(mg/day)

Pregnancy
(mg/day)
Lactation
(mg/day)

Infants
Undetermined

Undetermined
N/A

N/A
1-3

65
65

N/A
N/A
  1. - 8
110

110
N/A

N/A
  1. - 18
350

350
350

350
19+

350
350

350
350

Selecting a healthful diet
The 2000 Dietary Guidelines for Americans states, "Different foods
contain different nutrients and other healthful substances. No single
food can supply all the nutrients in the amounts you need" 61. If
you want more information about building a healthful diet, refer to
the Dietary Guidelines for Americans 61 (http://www.cnpp.usda.gov/Publications/DietaryGuidelines/2000/2000DGProfessionalBooklet.pdf)
and the US Department of Agriculture's Food Guide Pyramid 62 (http://www.nal.usda.gov/fnic/Fpyr/pyramid.html).

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Updated: 7/13/2009
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