It is not a weak base and there is no salt. First Name. Your Response. The accompanying bar graph shows the milk fat percentages in three dairy products. How many pounds each of whole milk and cream should be mixed to form lb of. There are two containers of milk. There is twice as much milk in the first container as in the second.
After using 2 gal. Each vessel contains some milk. How many vessels. If you add 5. Classify these mixtures as colloids, suspensions, or true solutions. It also maintains the conformation of nucleic acids and is essential for the structural function of proteins and mitochondria. It has long been suspected that magnesium may have a role in insulin secretion owing to the altered insulin secretion and sensitivity observed in magnesium-deficient animals [ 31 ].
Epidemiological studies have shown a high prevalence of hypomagnesaemia and lower intracellular magnesium concentrations in diabetics. Benefits of magnesium supplementation on the metabolic profile of diabetics have been observed in some, but not all, clinical trials, and so larger prospective studies are needed to determine if dietary magnesium supplementation is associated with beneficial effects in this group [ 32 ].
Recent epidemiological studies have suggested that a relatively young gestational age is associated with magnesium deficiency during pregnancy, which not only induces maternal and foetal nutritional problems but also leads to other consequences that might affect the offspring throughout life [ 33 ].
There is also evidence that magnesium and calcium compete with one another for the same binding sites on plasma protein molecules [ 13 , 34 ]. It was shown that magnesium antagonizes calcium-dependent release of acetylcholine at motor endplates [ 6 ]. It is anti-apoptotic in mitochondrial permeability transition and antagonizes calcium-overload-triggered apoptosis. Magnesium is important in health and disease, as will be discussed in more detail in this supplement in the article by Geiger and Wanner [ 37 ].
These observations indicate that various cell types handle magnesium quite differently, which is again different from calcium [ 10 ]. Myocardium, kidney parenchyma, fat tissue, skeletal muscle, brain tissue and lymphocytes exchange intracellular and extracellular magnesium at different rates.
In mammalian heart, kidney and adipocytes, total intracellular magnesium is able to exchange with plasma magnesium within 3—4 h [ 38 — 42 ]. In man, equilibrium for magnesium among most tissue compartments is reached very slowly, if at all [ 17 ]. Humans need to consume magnesium regularly to prevent magnesium deficiency, but as the recommended daily allowance for magnesium varies, it is difficult to define accurately what the exact optimal intake should be.
The Institute of Medicine recommends — mg and — mg for adult women and men, respectively. Other recommendations in the literature suggest a lower daily minimum intake of mg for men and — mg magnesium for women mg during pregnancy and lactation [ 2 , 7 , 10 , 18 ].
Nuts, seeds and unprocessed cereals are also rich in magnesium [ 15 ]. Legumes, fruit, meat and fish have an intermediate magnesium concentration. Low magnesium concentrations are found in dairy products [ 7 ]. It is noteworthy that processed foods have a much lower magnesium content than unrefined grain products [ 7 ] and that dietary intake of magnesium in the western world is decreasing owing to the consumption of processed food [ 45 ].
With the omnipresence of processed foods, boiling and consumption of de-mineralized soft water, most industrialized countries are deprived of their natural magnesium supply. On the other hand, magnesium supplements are very popular food supplements, especially in the physically active.
Magnesium homeostasis is maintained by the intestine, the bone and the kidneys. Magnesium—just like calcium—is absorbed in the gut and stored in bone mineral, and excess magnesium is excreted by the kidneys and the faeces Figure 4. Magnesium is mainly absorbed in the small intestine [ 21 , 15 , 46 ], although some is also taken up via the large intestine [ 7 , 10 , 47 ]. Two transport systems for magnesium in the gut are known as discussed in the article by de Baaij et al.
The majority of magnesium is absorbed in the small intestine by a passive paracellular mechanism, which is driven by an electrochemical gradient and solvent drag. A minor, yet important, regulatory fraction of magnesium is transported via the transcellular transporter transient receptor potential channel melastatin member TRPM 6 and TRPM7—members of the long transient receptor potential channel family—which also play an important role in intestinal calcium absorption [ 21 ].
It is noteworthy that intestinal absorption is not directly proportional to magnesium intake but is dependent mainly on magnesium status. The lower the magnesium level, the more of this element is absorbed in the gut, thus relative magnesium absorption is high when intake is low and vice versa.
When intestinal magnesium concentration is low, active transcellular transport prevails, primarily in the distal small intestine and the colon for details, see de Baaij et al. Magnesium balance. Values as indicated based on [ 7 ].
The conversion factor from milligrams to millimole is 0. The kidneys are crucial in magnesium homeostasis [ 18 , 49 — 51 ] as serum magnesium concentration is primarily controlled by its excretion in urine [ 7 ].
Magnesium excretion follows a circadian rhythm, with maximal excretion occurring at night [ 15 ]. It is noteworthy that magnesium transport differs from that of the most other ions since the major re-absorption site is not the proximal tubule, but the thick ascending limb of the loop of Henle.
The kidneys, however, may lower or increase magnesium excretion and re-absorption within a sizeable range: renal excretion of the filtered load may vary from 0. On one hand, the kidney is able to conserve magnesium during magnesium deprivation by reducing its excretion; on the other hand, magnesium might also be rapidly excreted in cases of excess intake [ 18 ].
While reabsorption mainly depends on magnesium levels in plasma, hormones play only a minor role e. Magnesium is essential for man and has to be consumed regularly and in sufficient amount to prevent deficiency. It is a cofactor in more than enzymatic reactions needed for the structural function of proteins, nucleic acids and mitochondria.
To date, three major approaches are available for clinical testing Table 4. The most common test for the evaluation of magnesium levels and magnesium status in patients is serum magnesium concentration [ 21 , 56 ], which is valuable in clinical medicine, especially for rapid assessment of acute changes in magnesium status [ 17 ]. However, serum magnesium concentration does not correlate with tissue pools, with the exception of interstitial fluid and bone.
It also does not reflect total body magnesium levels [ 17 , 57 ]. This situation is comparable to assessing total body calcium by measuring serum calcium, which, too, does not adequately represent total body content. Magnesium assessment [ 7 , 21 ]. In addition, there are individuals—in particular those with a subtle chronic magnesium deficiency—whose serum magnesium levels are within the reference range but who still may have a deficit in total body magnesium.
And vice versa: some people—though very few—have low serum magnesium levels but a physiological magnesium body content [ 17 ]. Moreover, serum magnesium might be higher in vegetarians and vegans than in those with omnivorous diets. The same applies to levels after short periods of maximal exercise as lower serum levels are observed after endurance exercises [ 58 , 59 ] and also during the third trimester of pregnancy.
There is also intra-individual variability [ 60 ]. Moreover, measurements are strongly affected by haemolysis and therefore by a delay in separating blood , and by bilirubin [ 59 ].
In healthy individuals, magnesium serum concentration is closely maintained within the physiological range [ 13 , 15 , 18 ]. This reference range is 0. According to Graham et al. Magnesium concentration in RBCs is generally higher than its concentration in serum [ 46 ] i.
Thus, when measuring magnesium serum levels, it is important to avoid haemolysis to prevent misinterpretation [ 17 , 22 ]. Although some limitations may apply, serum magnesium concentration is still used as the standard for evaluating magnesium status in patients [ 21 ].
It has proven helpful in detecting rapid extracellular changes. Another approach for the assessment of magnesium status is urinary magnesium excretion. This test is cumbersome, especially in the elderly, since it requires at least a reliable and complete h time frame [ 54 ].
As a circadian rhythm underlies renal magnesium excretion, it is important to collect a h urine specimen to assess magnesium excretion and absorption accurately. The results will provide aetiological information: while a high urinary excretion indicates renal wasting of magnesium, a low value suggests an inadequate intake or absorption [ 7 ].
A further refinement is the magnesium retention test. Retention of magnesium following acute oral or parenteral administration is used to assess magnesium absorption, chronic loss and status.
Changes in serum magnesium concentration and excretion following an oral magnesium load reflect intestinal magnesium absorption [ 7 , 63 ]. Magnesium retained during this test is retained in bone. Thus, the lower the bone magnesium content the higher the magnesium retention in this test [ 64 ]. The percentage of magnesium retained is increased in cases of magnesium deficiency and is inversely correlated with the concentration of magnesium in bone [ 65 , 66 ].
This test quantifies the major exchangeable pool of magnesium, providing a more sensitive index of magnesium deficiency than simply measuring serum magnesium concentration. Standardization of this test, however, is lacking [ 22 ]. Magnesium exists in three different isotopes: Radioactive tracer elements in ion uptake assays allow the calculation of the initial change in the ion content of the cells.
However, the radioactive half-life of the most stable radioactive magnesium isotope— [28] Mg—is only 21 h, restricting its use. Although studies with isotopes of magnesium can provide important information, they are limited to research [ 7 ].
Surrogates for magnesium i. They were used to mimic the properties of magnesium in some enzymatic reactions, and radioactive forms of these elements were successfully employed in cation transport studies.
Assessment of total serum magnesium concentration is the most practicable and inexpensive approach for the detection of acute changes in magnesium status. However, one should bear in mind that serum magnesium concentration does not reflect the patient's magnesium status accurately as it does not correlate well with total magnesium body content.
The definition of magnesium deficiency seems simpler than it is, primarily because accurate clinical tests for the assessment of magnesium status are still lacking. Evaluation of serum magnesium concentration and collection of a h urine specimen for magnesium excretion are at present the most important laboratory tests for the diagnosis of hypomagnesaemia.
The next step would be to perform a magnesium retention test [ 7 ]. A particularly high incidence of hypomagnesaemia is observed in intensive care units. Furthermore, a significant association has been reported between hypomagnesaemia and esophageal surgery [ 70 ]. In these severely ill patients, nutritional magnesium intake was probably insufficient. Certain drugs have been associated with magnesium wasting although the relationship between these factors remains unclear , putting the afflicted patients at an increased risk for acute hypomagnesaemia.
Such medications include aminoglycosides, cisplatin, digoxin, furosemide, amphotericin B and cyclosporine A [ 67 , 70 ] Table 5. Moreover, it was observed that in patients with severe hypomagnesaemia, mortality rates increase [ 67 , 70 ].
Therefore, assessment of magnesium status is advised, particularly in those who are critically ill. When hypomagnesaemia is detected, one should address—if identifiable—the underlying pathology to reverse the depleted status [ 73 ]. Hypomagnesaemia has been linked to poor condition malignant tumours, cirrhosis or cerebrovascular disease [ 70 ] and a number of other ailments. Deficiencies might also be triggered by increased magnesium excretion in some medical conditions such as diabetes mellitus, renal tubular disorders, hypercalcaemia, hyperthyroidism or aldosteronism or in the course of excessive lactation or use of diuretics Table 5.
Compartmental redistribution of magnesium in illnesses such as acute pancreatitis might be another cause of acute hypomagnesaemia [ 7 ]. In addition, several inherited forms of renal hypomagnesaemia exist [ 88 ]. These genetic changes led to the detection of various transporters see de Baaij et al. Diagnosis of chronic hypomagnesaemia is difficult as there may be only a slightly negative magnesium balance over time. There is equilibrium among certain tissue pools, and serum concentration is balanced by magnesium from bone.
Thus, there are individuals with a serum magnesium concentration within the reference interval who have a total body deficit for magnesium. Magnesium levels in serum and h urine samples may be normal, and so parenteral administration of magnesium with assessment of retention should be considered if in doubt [ 7 ].
Chronic latent magnesium deficiency has been linked to atherosclerosis, myocardial infarction, hypertension see also Geiger and Wanner [ 37 ] in this supplement. Clinical signs of hypo- and hypermagnesaemia overlap often and are rather non-specific.
Manifestations of hypomagnasaemia might include tremor, agitation, muscle fasciculation, depression, cardiac arrhythmia and hypokalaemia [ 6 , 10 , 67 ] Table 6. Early signs of magnesium deficiency include loss of appetite, nausea, vomiting, fatigue and weakness [ 67 ].
As magnesium deficiency worsens, numbness, tingling, muscle contractions, cramps, seizures, sudden changes in behaviour caused by excessive electrical activity in the brain, personality changes [ 67 ], abnormal heart beat and coronary spasms might occur. Severe hypomagnesaemia is usually accompanied by other imbalances of electrolytes such as low levels of calcium and potassium in the blood for mechanisms, see de Baaij et al.
However, even in patients with severe hypomagnesaemia, clinical signs associated with magnesium deficiency may be absent [ 7 ]. In addition, there seems to be a greater likelihood of clinical symptoms with a rapid decrease in serum magnesium concentration compared with a more gradual change.
Therefore, physicians should not wait for clinical signs to occur before checking serum magnesium levels [ 7 ]. Clinical and laboratory manifestations of hypomagnesaemia. Reprinted from [ 7 ], with permission from Elsevier. As the kidneys play a crucial role in magnesium homeostasis, in advanced chronic kidney disease, the compensatory mechanisms start to become inadequate and hypermagnesaemia may develop see Cunningham et al [ 28 ] in this supplement. Symptomatic hypermagnesaemia may be caused by excessive oral administration of magnesium salts or magnesium-containing drugs such as some laxatives [ 89 ] and antacids [ 14 ], particularly when used in combination in the elderly and when renal function declines [ 8 , 67 , 90 — 94 ].
In addition, hypermagnesaemia may be iatrogenic, when magnesium sulphate is given as an infusion for the treatment of seizure prophylaxis in eclampsia [ 67 , 95 ] or erroneously in high doses for magnesium supplementation [ 96 , 97 ]. Prevalence of—mostly undiagnosed—hypermagnesaemia in hospitalized patients is reported, varying from 5.
In intensive care patients, the prevalence of total hypermagnesaemia was reported as being These studies did not specify whether hypermagnesaemia in hospitalized patients was a pathological consequence of severe disease, or if it was iatrogenic, perhaps reflecting excessive magnesium supplementation in intensive care. Case reports exist of pre-term babies with extreme hypermagnesaemia—magnesium levels of All three infants survived. There are other reports about affected neonates whose mothers had gestational toxicosis and who had been treated with magnesium sulphate because of eclamptic convulsion [ 7 ].
Excessive magnesium ingestion and intoxication was also reported in association with drowning in the Dead Sea. Serum magnesium concentrations, as reported in the literature, vary widely among patients with similar signs and symptoms. In the beginning, no immediate clinical signs may be present and hypermagnesaemia might stay undetected for sometime [ 67 ]. Moderately elevated serum magnesium levels may be associated with hypotension, cutaneous flushing, nausea and vomiting, but these symptoms mostly occur only upon infusion of magnesium sulphate.
At higher concentrations, magnesium might lead to neuromuscular dysfunction, ranging from drowsiness to respiratory depression, hypotonia, areflexia and coma in severe cases. Cardiac effects of hypermagnesaemia may include bradycardia; uncharacteristic electrocardiogram findings such as prolonged PR, QRS and QT intervals, complete heart block, atrial fibrillation and asystole. However, these findings are neither diagnostic nor specific for this metabolic abnormality [ ] Table 7. Absence of deep tendon reflexes might help diagnose excess magnesium levels [ 7 ].
At these levels, severe muscle weakness has also been observed [ 21 ] Table 7. In cases of mild hypomagnesaemia in otherwise healthy individuals, oral magnesium administration is used successfully [ 68 ].
Acute and chronic oral magnesium supplementation has been described as well tolerated with a good safety profile [ , ]. Intravenous administration of magnesium, mostly as magnesium sulphate, should be used when an immediate correction is mandatory as in patients with ventricular arrhythmia and severe hypomagnesaemia [ ]. Treatment of patients with symptomatic hypermagnesaemia includes discontinuation of magnesium administration, use of supportive therapy and administration of calcium gluconate [ 6 , ].
Treatment of severe, symptomatic hypermagnesaemia may require haemodialysis [ 7 ]. Mild hypo- and hypermagnesaemia are quite common, especially in hospitalized patients, and may not be associated with clinical symptoms. Severe hypo- and hypermagnesaemia show partially overlapping symptoms, making diagnosis difficult without assessment of serum magnesium concentration.
The chemistry of magnesium is unique among cations of biological relevance. Magnesium is essential for man and is required in relatively large amounts. However, hypomagnesaemia is rather common, in particular, in hospitalized patients.
Moreover, as the intake of refined foods increases—as appears to be the case in developed countries—magnesium deficiency will most likely evolve into a more common disorder. Nonetheless, total serum magnesium is rarely measured in clinical practice.
Despite some limitations, the assessment of serum magnesium concentration is inexpensive and easy to employ and provides important information about magnesium status in patients. Ronald J. As basic knowledge comes from these publications, we often quoted his work. Fresenius also made an unrestricted educational grant to meet the cost of preparing this article.
Conflict of interest statement. National Center for Biotechnology Information , U. Journal List Clin Kidney J v. Clin Kidney J. Wilhelm Jahnen-Dechent 1 and Markus Ketteler 2. Author information Copyright and License information Disclaimer.
Medizinische Klinik, Coburg, Germany. Corresponding author. Correspondence and offprint requests to : Wilhelm Jahnen-Dechent; E-mail: ed. All rights reserved. For permissions, please e-mail: journals. For commercial re-use, please contact journals. This article has been cited by other articles in PMC. Abstract As a cofactor in numerous enzymatic reactions, magnesium fulfils various intracellular physiological functions.
Keywords: magnesium, physicochemical properties, physiological function, regulation, hypomagnesaemia, hypermagnesaemia. Introduction Magnesium is the eighth most common element in the crust of the Earth [ 1 , 2 ] and is mainly tied up within mineral deposits, for example as magnesite magnesium carbonate [MgCO 3 ] and dolomite.
Chemical characteristics Magnesium is a Group 2 alkaline earth element within the periodic table and has a relative atomic mass of Open in a separate window. Table 1. Table 2. Table 3. Moreover, it is a natural calcium antagonist [8]. Magnesium consumption Humans need to consume magnesium regularly to prevent magnesium deficiency, but as the recommended daily allowance for magnesium varies, it is difficult to define accurately what the exact optimal intake should be.
Magnesium absorption and excretion Magnesium homeostasis is maintained by the intestine, the bone and the kidneys. Assessment of magnesium status Serum magnesium concentration To date, three major approaches are available for clinical testing Table 4.
Table 4. Magnesium in: Serum Red blood cells a Leucocytes b Muscle c Metabolic assessment via: Balance studies Isotopic analyses Renal excretion of magnesium Retention of magnesium, following acute administration Free magnesium levels with: Fluorescent probes d Ion-selective electrodes e Nuclear magnetic resonance spectroscopy f g Metallochrome dyes. Application of fluorescent dyes, however, is limited because the major fluorescent dye for magnesium mag-fura 2 has a higher affinity for calcium than for magnesium.
Major advantages are that readings can be made over long time spans. In contrast to dyes, very little extra ion buffering capacity has to be added to the cells, and direct measurement of the ion flux across the membrane of a cell is possible with every ion passing across the membrane contributing to the result.
Nonetheless, ion-selective electrodes for magnesium are not entirely selective for ionized magnesium. A correction is applied based on the ionized calcium concentration [ 10 ]. With this technique, only content, not uptake, can be quantified.
Twenty-four-hour excretion in urine Another approach for the assessment of magnesium status is urinary magnesium excretion. Assessing magnesium status is difficult as most magnesium resides inside cells or bones.
The most common method for measuring your magnesium status is by measuring the serum magnesium levels, even though this has little correlation with total body magnesium levels or concentrations found in specific tissues. The following signs could indicate you are deficient in magnesium:. It should be noted that, with Hypomagnesemia, there is an increased excretion of potassium by the kidneys, resulting in a condition known as hypokalaemia low potassium.
Symptoms of this can include weakness, fatigue, constipation, muscle cramping, palpitations and, in more severe cases paralysis, and respiratory failure.
Eating magnesium-rich foods found in both plant and animal sources such as seeds and nuts along with whole grains, beans and leafy green vegetables is one way of obtaining magnesium. For reasons discussed earlier, obtaining sufficient magnesium from food sources and diet alone may not always be achievable, particularly if you are showing signs of severe magnesium depletion.
It is generally accepted, and referred to in many articles such as this on "Magnesium metabolism and perturbations in the elderly" ,that magnesium requirements increase in the elderly. Supplementation with magnesium supplements in order to support your magnesium requirements is one way of adequately achieving your necessary daily intake.
Because magnesium is a very chemically active metallic element, it occurs naturally only in combination with other elements.
They occur as organic and inorganic magnesium salts. Each combination with magnesium provides different amounts of elemental magnesium. The amount of magnesium and its bioavailability determine the effectiveness of the supplement. Bioavailability refers to how easily a substance is absorbed by the body and refers to the proportion of the administered substance capable of being absorbed along with that available for cellular uptake, use or storage.
In short, the amount of magnesium that your tissues can use readily is based on how soluble the magnesium product is and the amount of elemental magnesium that is released. Another factor that affects the absorption of magnesium is the existing magnesium levels of the individual, as magnesium will be less rapidly absorbed if body levels are already adequate and excreted through the urine or stools if given in excess.
Those forms that dissolve well in liquid are more completely absorbed in the gut than less soluble forms. Organic magnesium salts are, in general, more soluble than inorganic magnesium salts.
Magnesium citrate is a form of magnesium bound to citric acid, an acid found naturally in citrus fruits giving them a tart, sour flavour. Some research, such as this clinical trial on the bioavailability of different forms of magnesium , indicates this is one of the most bioavailable forms of magnesium.
When the magnesium citrate reaches the small intestine, it attracts enough water to induce defecation. The extra water helps create more faeces, stimulating bowel motility and, therefore, may have a mild laxative effect.
This form of magnesium functions best on an empty stomach followed by a full glass of water or juice to aid absorption. Researchers have demonstrated that magnesium bioavailability is greater in citrate than oxide , taking the pH of stomach acid and alkalinity of pancreas into consideration.
The weak ionic bonds of magnesium and malic acid are easily broken, making it readily soluble in the body and therefore well absorbed. Some people report that magnesium malate is gentler on your system and may have less of a laxative effect than some other magnesium supplements.
Magnesium Ascorbate is a buffered non- acidic form of vitamin C and magnesium. It is a neutral salt that has a significantly higher gastrointestinal tolerance than some of the other forms. It offers a source of both magnesium and vitamin C with good bioavailability. This is a salt that combines magnesium and oxygen. It is completely ionized across a large pH range, 2 found in stomach acid to 7. Magnesium chloride has the chloride part of its compound to produce hydrochloric acid in the stomach and enhance its absorption.
This is particularly suitable for anybody with low stomach acid production of stomach HCl is known to decline with age. Magnesium sulfate is also known as Epsom salts. It contains magnesium; sulphur and oxygen. It is the main preparation of intravenous magnesium.
Bioavailability is limited and variable with degrees of mild diarrhoea, as shown in this research article on the absorption of magnesium from orally administered magnesium sulfate.
It is often used as a treatment for constipation. Magnesium Phosphate is practically insoluble in water. Magnesium is bound to phosphate in teeth and bone. Magnesium Carbonate is nearly insoluble, however, in the presence of stomach acid HCl it is converted to magnesium chloride. In large doses this form may have a mild laxative effect. Magnesium hydroxide has a relatively high percentage of elemental magnesium but has a low solubility in water, suggesting poor absorption.
When in a suspension in water, it is often called milk of magnesia, used as an antacid or laxative. Although it has a high percentage of elemental magnesium, the magnesium ion is very poorly absorbed from the intestinal tract, drawing water from the surrounding tissues by osmosis.
Magnesium Bisglycinate is a chelated form of magnesium and the amino acid glycine. The presence of glycine has a buffering effect on the chelated magnesium, which improves the solubility of the whole compound and, therefore, improves its bioavailability. Absorption of magnesium is a complex process, which has a major impact on the relative bioavailability of supplements.
All are suitable for restoring magnesium status under normal physiological conditions, it is a case of establishing which one is right for you and consulting your healthcare practitioner and conducting research into intestinal absorption and factors influencing the bioavailability of magnesium. Although magnesium supplements are generally considered safe, you should check with your healthcare practitioner before taking them — especially if you have a medical condition.
High doses of magnesium can result in diarrhoea. Why is there insufficient Magnesium in your diet? Reduced Magnesium due to processing Food processing is any method used to turn fresh foods into food products. Reduced Magnesium levels in soil Some commonly used pesticides can bind and immobilise certain minerals, potentially decreasing the amount of magnesium in the soil and, therefore, also some crops, as discussed in this article on reduced nutrient concentrations in soybeans.
The use of herbicides and pesticides also kill off worms and bacteria in the soil.
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