Everything about magnesium

What is magnesium

Magnesium is an abundant mineral in the body, naturally found in many foods, added to other foods, provided as a dietary supplement, and found in certain drugs (such as antacids and laxatives). Magnesium is a cofactor for more than 300 enzyme systems and can regulate a variety of biochemical reactions in the body, including protein synthesis, muscle and nerve function, blood sugar control, and blood pressure regulation . Magnesium is necessary for energy production, oxidative phosphorylation, and glycolysis. It contributes to the structural development of bones and is necessary 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. This process is important for nerve impulse transmission, muscle contraction, and normal heart rhythm .

Adults contain approximately 25 grams of magnesium, of which 50% to 60% is found in bones, and most of the rest is found in soft tissues . Less than 1% of total magnesium is present in serum, and these levels are strictly controlled. The normal serum magnesium concentration ranges between 0.75 and 0.95 millimoles (mmol)/L . Hypomagnesemia is defined as a serum magnesium level of less than 0.75 mmol/L . Magnesium homeostasis is mainly controlled by the kidneys, which usually excrete approximately 120 mg of magnesium into the urine every day . When the magnesium status is low, urinary excretion decreases .

Assessing magnesium status is difficult because most magnesium is found in cells or bones . The most common and easily available method for assessing magnesium status is to measure serum magnesium concentration, although serum levels have little correlation with systemic magnesium levels or concentrations in specific tissues . Other methods of assessing magnesium status include measuring the magnesium concentration in red blood cells, saliva, and urine; measuring the ionized magnesium concentration in blood, plasma, or serum; and performing a magnesium load (or "tolerance") test. No method is considered satisfactory . Some experts, but not others, believe that tolerance testing (measurement of urinary magnesium after parenteral infusion of a certain dose of magnesium) is the best way to assess the magnesium status of adults. In order to fully assess the magnesium status, laboratory tests and clinical evaluations may be required .

Recommended intake

The Dietary Reference Intake (DRI) established by the Food and Nutrition Board (FNB) of the Institute of Medicine of the National Academy of Sciences (formerly the National Academy of Sciences) provides recommendations for the intake of magnesium and other nutrients . DRI is a general term for a set of reference values ​​used to plan and evaluate the nutritional intake of healthy people. These values ​​vary by age and gender, and include:

• Recommended Dietary Intake (RDA): The average daily intake is sufficient to meet the nutritional needs of almost all (97%–98%) healthy individuals; it is usually used to plan a nutritious diet for individuals.
• Adequate intake (AI): It is assumed that this level of intake will ensure adequate nutrition; this is true when there is insufficient evidence to establish an RDA.
• Estimated Average Requirement (EAR): The average daily intake that is estimated to meet the needs of 50% of healthy individuals; it is usually used to assess the nutritional intake of a population and plan a nutritious diet for them; it can also be used to assess the nutritional intake of individuals.入量。 Into the amount.
• Tolerable maximum intake (UL): The maximum daily intake is unlikely to cause adverse health effects.

Table 1 lists the current RDA for magnesium . For babies from birth to 12 months, FNB has established an AI for magnesium, which is equivalent to the average magnesium intake of healthy breastfed infants, and added solid foods from 7-12 months of age.

*Adequate Intake (AI)

Source of Magnesium

FOOD

Magnesium is widely distributed in plant and animal foods and beverages. Leafy green vegetables, such as spinach, beans, nuts, seeds, and whole grains, are good sources . Generally speaking, foods containing dietary fiber can provide magnesium. Magnesium is also added to some breakfast cereals and other fortified foods. Certain types of food processing, such as refining grains by removing nutrient-rich germ and bran, can significantly reduce magnesium content . Table 2 lists selected food sources of magnesium.

Tap water, mineral water, and bottled water may also be sources of magnesium, but the content of magnesium in the water varies depending on the source and brand (from 1 mg/liter to more than 120 mg/liter) .

About 30% to 40% of dietary magnesium is normally absorbed by the body .

*DV = daily value. The U.S. Food and Drug Administration (FDA) developed DV to help consumers compare the nutritional content of foods and dietary supplements in the context of a total diet. The magnesium DV for adults and children 4 years and older is 420 mg . Unless magnesium is added to the food, the FDA does not require food labels to list the magnesium content. Foods that provide 20% or more of the DV are considered high sources of nutrition, but foods that provide a lower percentage of DV also contribute to a healthy diet.

The United States Department of Agriculture (USDA) lists the nutritional content of many foods and provides a comprehensive list of magnesium-containing foods arranged by nutritional content and food name .

DIETARY SUPPLEMENTS

Magnesium supplements come in many forms, including magnesium oxide, citrate, and magnesium chloride . The supplement facts panel on the dietary supplement label states the content of elemental magnesium in the product , not the weight of the entire magnesium compound.

Different types of magnesium supplements have different absorption of magnesium. The magnesium form that dissolves well in liquids is more completely absorbed by the intestines than the less soluble form . Small studies have found that compared with magnesium oxide and magnesium sulfate, magnesium in the form of aspartic acid, citric acid, lactate and chloride is more completely absorbed and has a higher bioavailability . A study found that taking a very high dose of zinc from supplements (142 mg/day) interferes with the absorption of magnesium and disrupts the magnesium balance in the body .

DRUG

Magnesium is the main component of some laxatives . For example, Phillips' Milk of Magnesia® provides 500 mg of elemental magnesium (as magnesium hydroxide) per tablespoon; the instructions suggest that teenagers and adults take 4 tablespoons a day . (Although this dose of magnesium is far above the safe upper limit, some magnesium is not absorbed due to the laxative effect of the drug.) Magnesium is also included in some drugs for the treatment of heartburn and stomach upset caused by acid indigestion . For example, Extra Strength Rolaids® provides 55 mg of elemental magnesium (as magnesium hydroxide) per tablet , although Tums® does not contain magnesium .

Magnesium intake and status

Dietary surveys of Americans consistently show that many people consume less than the recommended amount of magnesium. An analysis of 2013-2016 National Health and Nutrition Examination Survey (NHANES) data found that 48% of Americans of all ages consume less magnesium from food and beverages than their respective EAR; adult males 71 years and older And the intake of adolescent men and women is most likely to be lower . In a study using NHANES 2003-2006 data to assess adult mineral intake, dietary supplement users had a higher average intake of magnesium from food alone (350 mg for men and 267 mg for women, equal to or Slightly more than their respective EAR intake)) than non-users (268 mg for men and 234 mg for women) . When supplements are included, the average magnesium intake is 449 mg for men and 387 mg for women, which is much higher than the EAR level.

There is currently no data on the status of magnesium in the United States. Determining dietary magnesium intake is a common indicator for evaluating magnesium status. Since 1974, NHANES has not determined the serum magnesium levels of its participants , and magnesium has not been evaluated in routine electrolyte tests in hospitals and clinics .

Magnesium deficiency

In otherwise healthy people, symptomatic magnesium deficiency due to low dietary intake is not common because the kidneys restrict the urinary excretion of this mineral . However, low or excessive loss of magnesium due to certain health conditions, chronic alcoholism, and/or the use of certain drugs can lead to magnesium deficiency.

Early signs of magnesium deficiency include loss of appetite, nausea, vomiting, fatigue, and weakness. As the magnesium deficiency worsens, there may be numbness, tingling, muscle contractions and cramps, seizures, personality changes, abnormal heart rhythms, and coronary artery spasms . Severe magnesium deficiency can lead to hypocalcemia or hypokalemia (low serum calcium or potassium levels, respectively) because mineral homeostasis is disrupted .

Groups at risk of magnesium deficiency

Magnesium deficiency occurs when the intake is lower than the RDA but higher than the amount needed to prevent a significant deficiency. The following populations are more likely to be at risk of magnesium deficiency than others because they usually consume insufficient amounts or their medical conditions (or taking medications) reduce the absorption of magnesium in the intestines or increase the loss of magnesium in the body.

PEOPLE WITH GASTROINTESTINAL DISORDERS

Chronic diarrhea and fat malabsorption caused by Crohn's disease, gluten-sensitive enteropathy (celiac disease), and regional enteritis can lead to magnesium consumption over time . Removal or bypassing of the small intestine, especially the ileum, usually results in malabsorption and loss of magnesium .

TYPE 2 DIABETES PATIENTS

Patients with insulin resistance and/or type 2 diabetes may experience magnesium deficiency and increased urinary magnesium excretion . Magnesium loss appears to be secondary to a higher concentration of glucose in the kidneys, which increases urine output .

PEOPLE WITH ALCOHOL DEPENDENCE

Magnesium deficiency is common in patients with chronic alcoholism . In these people, poor dietary intake and nutritional status; gastrointestinal problems, including vomiting, diarrhea, and steatorrhea (fatty stools) caused by pancreatitis; renal insufficiency, excessive excretion of magnesium in the urine; phosphate Depletion; vitamin D deficiency; acute alcoholic ketoacidosis; and hyperaldosteronism secondary to liver disease may all cause a decrease in magnesium status .

THE ELDERLY

The dietary magnesium intake of the elderly is lower than that of the young . In addition, with age, the absorption of magnesium in the intestines will decrease, while the excretion of magnesium by the kidneys will increase . Older people are also more likely to suffer from chronic diseases or take medications that change magnesium status, which increases their risk of magnesium consumption .

Magnesium and health

Habitual intake of low magnesium can lead to changes in biochemical pathways, which will increase the risk of disease over time. This section focuses on four diseases and disorders that magnesium may be involved in: hypertension and cardiovascular disease, type 2 diabetes, osteoporosis, and migraine.

HYPERTENSION AND CARDIOVASCULAR DISEASE

Hypertension is a major risk factor for heart disease and stroke. However, studies to date have found that magnesium supplementation can only lower blood pressure to a small extent at best. A meta-analysis of 12 clinical trials found that magnesium supplementation for 545 hypertensive participants for 8-26 weeks resulted in only a small decrease in diastolic blood pressure (2.2 mmHg) . The dosage of magnesium ranges from approximately 243 to 973 mg/day. The authors of another meta-analysis of 22 studies of 1,173 adults with normal blood pressure and hypertension concluded that magnesium supplementation for 3-24 weeks can reduce systolic blood pressure by 3-4 mmHg and diastolic blood pressure by 2-3 mmHg . When the supplementary magnesium intake of the participants in the nine crossover design trials exceeds 370 mg/day, the effect will be greater. Due to the addition of fruits and vegetables, diets containing more magnesium, more low-fat or non-fat dairy products, and diets with lower total fat content have been shown to reduce systolic blood pressure and diastolic blood pressure by an average of 5.5 and 3.0 mmHg, respectively . However, this diet to stop high blood pressure (DASH) diet also increases the intake of other nutrients, such as potassium and calcium, which are related to lowering blood pressure, so any independent contribution of magnesium cannot be determined.

Several prospective studies have examined the association between magnesium intake and heart disease. The Community Atherosclerosis Risk Study assessed the heart disease risk factors and serum magnesium levels of 14,232 white and African American men and women aged 45 to 64 years old at baseline . During an average of 12 years of follow-up, compared with individuals in the lowest quartile, individuals in the highest quartile of the normal physiological range of serum magnesium (at least 0.88 mmol/L) had a 38% lower risk of sudden cardiac death. 0.75 mmol/L or less). However, dietary magnesium intake has nothing to do with the risk of sudden cardiac death. Another prospective study followed 88,375 female nurses in the United States to determine whether the serum magnesium levels measured in the early stages of the study and the assessment of magnesium intake from food and supplements every 2 to 4 years are consistent with the 26-year follow-up period Related to sudden cardiac death . Compared with the lowest quartile of intake and plasma magnesium concentration, the risk of sudden cardiac death in the highest women was reduced by 34% and 77%, respectively. Another prospective population study of 7,664 adults with no cardiovascular disease between the ages of 20 and 75 in the Netherlands found that low urinary magnesium excretion (a sign of low dietary magnesium intake) is associated with higher ischemic heart disease The risk-related follow-up period was 10.5 years. Plasma magnesium concentration has nothing to do with the risk of ischemic heart disease . A systematic review and meta-analysis of a prospective study found that a higher serum magnesium level was significantly associated with a lower risk of cardiovascular disease, and a higher dietary magnesium intake (up to about 250 mg/day) was associated with a lower risk of cardiovascular disease. Related to cardiovascular disease risk. Ischemic heart disease caused by reduced blood supply to the myocardium .

Higher magnesium intake may reduce the risk of stroke. In a meta-analysis of 241,378 participants that included 7 prospective trials, an additional 100 mg/day of magnesium in the diet was associated with an 8% reduction in overall stroke risk, especially ischemic rather than hemorrhagic stroke . However, one of the limitations of such observational studies is that they may be confused with other nutrients or dietary ingredients that may affect the risk of stroke.

A large, well-designed clinical trial is needed to better understand the contribution of magnesium in foods and dietary supplements to heart health and primary prevention of cardiovascular disease .

TYPE 2 DIABETES

A diet high in magnesium is associated with a significantly lower risk of diabetes, which may be due to the important role of magnesium in glucose metabolism . Hypomagnesemia may increase insulin resistance, which usually occurs before diabetes, or it may be the result of insulin resistance . Diabetes will lead to an increase in the loss of magnesium in the urine, and subsequent magnesium deficiency may impair the secretion and function of insulin, thereby making diabetes control evil .

Most studies on magnesium intake and the risk of type 2 diabetes are prospective cohort studies. A meta-analysis of seven of these studies (including 286,668 patients and 10,912 diabetic patients with 6 to 17 years of follow-up) found that for every 100 mg/day increase in total magnesium intake, the risk of diabetes was significantly reduced. 15% . Another meta-analysis of 8 prospective cohort studies followed 271,869 men and women between the ages of 4 and 18 and found a significant negative correlation between food intake of magnesium and the risk of type 2 diabetes ; When comparing the highest and lowest intakes, the relative risk is reduced by 23% .

A 2011 meta-analysis of prospective cohort studies on the association between magnesium intake and the risk of type 2 diabetes included 13 studies with a total of 536,318 participants and 24,516 cases of diabetes . The average follow-up time is 4 to 20 years. Researchers found that there was a dose-responsive negative correlation between magnesium intake and the risk of type 2 diabetes, but this association only reached statistical significance in overweight (body mass index [BMI] 25 or higher), and in normal weight Individual (BMI below 25). Similarly, the limitation of these observational studies is that they may be confused with other dietary components or lifestyle or environmental variables related to magnesium intake.

Only a few small short-term clinical trials have investigated the potential effects of magnesium supplementation on the control of type 2 diabetes, with conflicting results . For example, in a clinical trial in Brazil, 128 patients with poorly controlled diabetes received a placebo or a supplement containing 500 mg/day or 1,000 mg/day of magnesium oxide (providing 300 or 600 mg of elemental magnesium, respectively) . After 30 days of supplementation, participants who received larger doses of supplements had increased plasma, cell, and urine magnesium levels, and their blood sugar control improved. In another small trial in Mexico, participants with type 2 diabetes and hypomagnesemia received a liquid magnesium chloride supplement (providing 300 mg/day of elemental magnesium) for 16 weeks, compared with participants who received a placebo , Fasting blood glucose and glycosylated hemoglobin concentrations were significantly reduced, and their serum magnesium levels became normal . In contrast, among the 50 patients with type 2 diabetes taking insulin, neither supplementation with magnesium aspartate (providing 369 mg/day of elemental magnesium) nor taking placebo for 3 months had any effect on blood sugar control. Influence.

The American Diabetes Association pointed out that there is insufficient evidence to support the routine use of magnesium to improve blood sugar control in diabetic patients . It further stated that there is no clear scientific evidence that vitamin and mineral supplements are beneficial for diabetic patients who do not have underlying nutritional deficiencies.

OSTEOPOROSIS

Magnesium participates in bone formation and affects the activities of osteoblasts and osteoclasts . Magnesium also affects the concentration of the active form of parathyroid hormone and vitamin D, which are the main regulators of bone homeostasis. Several population-based studies have found that there is a positive correlation between the magnesium intake of men and women and bone mineral density . Other studies have found that women with osteoporosis have lower serum magnesium levels than women with osteopenia and women without osteoporosis or osteopenia . These and other findings suggest that magnesium deficiency may be a risk factor for osteoporosis .

Although the number is limited, studies have shown that increasing the intake of magnesium from food or supplements may increase bone mineral density in postmenopausal and elderly women . For example, a short-term study found that compared with placebo, 20 postmenopausal women with osteoporosis taking 290 mg/day of elemental magnesium (such as magnesium citrate) for 30 consecutive days can inhibit bone turnover, which indicates that bone quality Loss is reduced .

A diet that provides recommended levels of magnesium can enhance bone health, but further research is needed to clarify the role of magnesium in the prevention and management of osteoporosis.

MIGRAINE

Magnesium deficiency is related to factors that induce headaches, including neurotransmitter release and vasoconstriction . The serum and tissue magnesium levels of migraine patients are lower than those of patients without migraine.

However, research on the use of magnesium supplements to prevent or reduce migraine symptoms is limited. Three of four small, short-term, placebo-controlled trials found that the frequency of migraines was moderately reduced in patients given magnesium up to 600 mg/day . The authors of the migraine prevention review recommend that 300 mg of magnesium taken twice a day, alone or in combination with medications, can prevent migraine .

In their updated evidence-based guidelines, the American Academy of Neurology and the American Headache Society concluded that magnesium therapy "may be effective" in preventing migraine . Since the typical dose of magnesium used to prevent migraines exceeds UL, this treatment can only be used under the guidance and supervision of a healthcare provider.

Health hazards of excessive magnesium

Excessive magnesium in food does not pose a threat to the health of healthy people, because the kidneys will remove excess magnesium in urine . However, high doses of magnesium in dietary supplements or medications often cause diarrhea, accompanied by nausea and abdominal cramps . It has been reported that the most common forms of magnesium that cause diarrhea include magnesium carbonate, magnesium chloride, magnesium gluconate and magnesium oxide . The diarrhea and laxative effects of magnesium salt are due to the osmotic activity of the unabsorbed salt in the intestine and colon and the stimulation of gastric motility .

Very large doses of magnesium laxatives and antacids (usually providing more than 5,000 mg/day of magnesium) have been associated with magnesium poisoning , including fatal hypermagnesemia in a 28-month-old boy and an elderly person . Symptoms of magnesium poisoning usually appear after the serum concentration exceeds 1.74-2.61 mmol/L, including hypotension, nausea, vomiting, facial flushing, urinary retention, intestinal obstruction, depression, and drowsiness, and then progress to muscle weakness, dyspnea, and extreme hypotension Blood pressure, arrhythmia, and cardiac arrest . The risk of magnesium poisoning increases with impaired renal function or renal failure because the ability to remove excess magnesium is reduced or lost .

FNB has established a magnesium UL, which is only applicable to healthy infants, children and adults as supplementary magnesium (see Table 3) .

Interaction with drugs

Several types of drugs may interact with magnesium supplements or affect magnesium status. Some examples are provided below. People who take these and other medications on a regular basis should discuss their magnesium intake with their healthcare provider.

BISPHOSPHONATE

Supplements or medications rich in magnesium can reduce the absorption of oral bisphosphonates used to treat osteoporosis, such as alendronate (Fosamax®) . Use magnesium-rich supplements or medications and oral bisphosphonates should be separated by at least 2 hours .

ANTIBIOTIC

Magnesium can form insoluble complexes with tetracyclines (such as demecycline (Declomycin®) and doxycycline (Vibramycin®)) and quinolone antibiotics (such as ciprofloxacin (Cipro®) and levofloxacin (Levaquin®)). These antibiotics should be taken at least 2 hours before or 4-6 hours after taking magnesium supplements .

DIURETICS

Chronic treatment with loop diuretics (such as furosemide (Lasix®) and bumetanide (Bumex®)) and thiazide diuretics (such as hydrochlorothiazide (Aquazide H®) and acetonitrile (Edecrin®)) increases urine Loss of magnesium and lead in the liquid magnesium consumption . In contrast, potassium-sparing diuretics, such as amiloride (Midamor®) and spironolactone (Aldactone®), can reduce magnesium excretion .

PROTON PUMP INHIBITOR

Prescription proton pump inhibitor (PPI) drugs, such as esomeprazole magnesium (Nexium®) and lansoprazole (Prevacid®), can cause hypomagnesemia when taken for a long time (usually more than a year) . Under FDA review, magnesium supplements usually increase the low serum magnesium levels caused by PPI. However, in 25% of cases, supplements did not increase magnesium levels and patients had to stop PPI. The FDA recommends that healthcare professionals consider measuring the serum magnesium levels of patients before beginning long-term PPI treatment and regularly check the magnesium levels of these patients .

Magnesium and healthy eating

The Federal Government’s 2020-2025 Dietary Guidelines for Americans states that “because food provides a series of nutrients and other ingredients that are beneficial to health, nutritional needs should be met mainly through food.... In some cases, fortified foods and Dietary supplements are useful when the need for one or more nutrients cannot be met (for example, during specific life stages such as pregnancy)."

American 's Dietary Guidelines for healthy eating patterns described as:

• Includes various vegetables; fruits; cereals (at least half of whole grains); skimmed and low-fat milk, yogurt, and cheese; and oils.

  Whole grains and dark green leafy vegetables are good sources of magnesium. Low-fat milk and yogurt also contain magnesium. Some instant breakfast cereals are rich in magnesium.

• Including a variety of protein foods, such as lean meat; poultry; eggs; seafood; beans, peas and lentils; nuts and seeds; and soy products.

  Dried beans and legumes (such as soybeans, roasted beans, lentils, and peanuts) and nuts (such as almonds and cashews) provide magnesium.

• Limit the addition of foods and beverages with high sugar, saturated fat, and sodium content.

• Limit alcoholic beverages.

• Stay within your daily calorie requirements.