Carolyn Klempay
KNH 413
Nutrient Information
Medical Nutrition Therapy Nutrient
Magnesium
1. What is the nutrient?
Magnesium is a mineral that is found in the body and is presented naturally in foods.
Magnesium works with other enzyme systems that collaborate to regulate bodily reactions
including protein synthesis, muscle function, and blood pressure regulation. This nutrient
assists in the process of glycolysis, contributes to the structural development of bone, helps the
active transport of calcium and potassium, and contributes to normal heart rhythms.
2. What is the RDA/DRI for the nutrient?
Magnesium intake is based on the Dietary Reference Intake (DRI) information that
describes a general set of reference values used to assess the nutrition of healthy individuals.
These standards for the Recommended Daily Allowance (RDA) for magnesium differ based on
age and gender. A table which breaks down recommendations in a visual way is displayed
below.
Age
Birth to 6 months
7–12 months
1–3 years
4–8 years
9–13 years
14–18 years
19–30 years
31–50 years
51+ years
Male
30 mg*
75 mg*
80 mg
130 mg
240 mg
410 mg
400 mg
420 mg
420 mg
Female
30 mg*
75 mg*
80 mg
130 mg
240 mg
360 mg
310 mg
320 mg
320 mg
Pregnancy
400 mg
350 mg
360 mg
Lactation
360 mg
310 mg
320 mg
3. How is the nutrient metabolized?
On average, an adult body will contain about 25 grams of magnesium, the larger portion
being present in the bones, and the remaining in the soft tissues. About 30%-40% of the
dietary magnesium that is taken into the body is typically absorbed. The regulation of
magnesium levels in the body is highly controlled by proper kidney functioning which allows
excess mineral to be excreted in the urine or decreases excretion when magnesium reserves
are low. Magnesium levels, although very difficult to gain an accurate and precise
measurement of mineral status, can be measured through serum concentration evaluations.
4. What are food sources of the nutrient?
This mineral is common in many plant and animal sources of food, as well as various
beverages. Good sources of magnesium include green leafy vegetables such as spinach in
addition to whole grains, nuts, seeds, and legumes. A general rule states that foods which are
good sources of dietary fiber also tend to be good magnesium sources as well. Foods such as
breakfast cereals may be fortified with magnesium and contrarily, heavily processed foods may
be lower in magnesium due to the removal of nutrient-rich portions during the refining of
certain grains. Water that is from the tap or bottled may possess magnesium, however, the
amount varies greatly depending on water source and brand. Specific foods that are high in
magnesium include almonds, spinach, cashews, peanuts, cereal, soymilk, black beans,
edamame, peanut butter, whole wheat bread, avocado, brown rice, and plain low-fat yogurt. It
is not required by the FDA to list the magnesium content of foods in the nutrition facts label
unless the food has been fortified with the mineral.
5. What disease states alter the nutrients metabolism?
Individuals with gastrointestinal diseases are at risk for magnesium depletion over time.
These diseases can include Crohn’s disease, gluten-sensitive enteropathy (Celiac disease), or
enteritis. Instances in which the small intestine, particularly the ileum, is bypassed can usually
lead to loss of magnesium through malabsorption.
Type 2 Diabetes is another disease state that can alter the metabolism of magnesium
due to increased magnesium excretion. Because of increased glucose concentrations in the
kidneys, urinary magnesium output is increased as well, creating a mineral imbalance.
Alcoholism is a third disease state in which magnesium absorption and metabolism is
highly affected. Poor nutritional intake and dietary magnesium consumption, chronic vomiting,
diarrhea, and steatorrhea can lead to renal dysfunction and excessive magnesium excretion.
Vitamin D deficiency, alcoholic ketoacidosis, and liver disease are all contributing factors to a
decreased magnesium status in those who have alcohol dependence.
Lastly, older adults, even without diagnosis of a particular disease state, have lower
dietary intake of magnesium and higher risk for inadequate mineral metabolism. Absorption of
magnesium in the gut decreases with age and chronic illness or additional medications taken by
older adults create increased potential for disrupted magnesium metabolism.
6. What are the tests or procedures to assess the nutrient level in the body?
Assessing the nutrient magnesium in the body is somewhat difficult because most of
this mineral is housed inside cells or bone. Measuring the serum magnesium concentration is
the most commonly used method of mineral assessment. Although serum magnesium has very
little correlation to total bodily and specific tissue magnesium concentration, this method is
most readily available for use.
Additional testing procedures to evaluate magnesium concentration in the body include
measuring concentrations of magnesium in erythrocytes, saliva, urine, blood, plasma, and
serum magnesium through magnesium-loading or “tolerance” testing. Some researchers
consider the tolerance test to be the most accurate method of magnesium concentration
assessment. In this test, a parenteral infusion of a magnesium dosage is given and after,
urinary magnesium is measured to assess excretory properties. Ultimately, a combination of
clinical and laboratory assessments are needed to get the most accurate measurement of this
mineral’s presence in the body.
7. What are the drug-nutrient interactions?
Magnesium status has the potential to be affected when in combination with particular
medications and it is important that those who take these medications speak with a physician
about the possibility of medical concerns. Bisphosphatates used to treat osteoporosis may be
altered in effectiveness due to magnesium-containing supplements. Separate magnesium
supplements and bisphosphatate intake by at least two hours to prevent interactions.
Antibiotics and diuretics should also be taken several hours after or before taking magnesium
supplements due to the potential of interactions and increasing magnesium deficiency risks.
Proton pump inhibitors, when taken consistently for long periods of time, also have the ability
to cause hypomagnesemia. If this medication is necessary, regular measurements of
magnesium status should be taken and monitored for substantial changes.
8. How is the nutrient measured?
This nutrient is measured in grams or mmols in the body. Measurements are gained
through evaluation of serum magnesium levels in saliva, urine, and blood plasma. Additionally,
studying the results of concentrated magnesium intake, and excretory magnesium
measurements can assist in the measurement of this nutrient.
9. What is the Upper Tolerable Limit?
Tolerable upper limits for magnesium for infants, children, and adults apply only to
magnesium supplementation, not to dietary consumption. A table to display these Upper
Tolerable Limits is displayed below.
Age
Birth to 12 months
1–3 years
4–8 years
9–18 years
19+ years
Male
None established
65 mg
110 mg
350 mg
350 mg
Female
None established
65 mg
110 mg
350 mg
350 mg
Pregnant
350 mg
350 mg
Lactating
350 mg
350 mg
10. What are the physical signs of deficiency?
Physical signs of a magnesium deficiency include loss of appetite, nausea, vomiting,
fatigue, and weakness. These beginning signs can worsen as the deficiency increases and
additional physical signs are numbness, tingling sensations, muscle contractions, muscle
cramps, seizures, abnormal heart rhythms, coronary spasms, and changes in personality.
Extremely severe cases in the deficiency of this mineral may result in low serum calcium and
low serum potassium levels (hypocalcemia and hypokalemia respectively) due to the imbalance
and disruption in mineral homeostasis.
11. What are the physical signs of toxicity?
High magnesium levels due to excessive magnesium supplementation can result in
physical signs of diarrhea, nausea, and abdominal cramping. It is quite unlikely that magnesium
toxicity can result from dietary intake because of the kidney’s process of mineral regulation and
excretion. Severe cases of magnesium toxicity, when serum concentrations exceed 1.74-2.61
mmol/L, will ultimately lead to hypotension, nausea, vomiting, facial flushing, urine retention,
depression, and lethargy. These initial signs can worsen to muscle weakness, difficulty
breathing, extreme hypotension, irregularities in heartbeat, and even cardiac arrest.
Resources:
NIH. (2013, November 4). Magnesium. — Health Professional Fact Sheet. Retrieved April 21,
2014, from http://ods.od.nih.gov/factsheets/Magnesium-HealthProfessional/