Magnesium deficiency affects all body tissues. Symptoms of severe deficiency, which is rare, include irritability, personality changes, anorexia, weakness, tiredness, vertigo, convulsions, nervousness, muscle cramps and tremors, tongue jerks and tremors, involuntary eye movements, unsteady gait, irregular heartbeat, palpitations, low blood sugar and sustained muscle contraction. Loss of hair, swollen gums, and damage to the arteries resembling atherosclerosis are symptoms of advanced deficiency. Magnesium deficiency leads to low blood calcium levels.
Deficiency can occur due to malnutrition, surgery, serious burns, kidney disease, pancreatic inflammation, liver disease, absorption disorders, diabetes, hormonal disorders, cancer, heavy exercise and pregnancy. A high dietary intake of phosphate, calcium, vitamin D and saturated fats may also lead to deficiency. Alcoholics and those taking diuretics are particularly at risk as these drugs both cause large urinary magnesium losses.
Marginal magnesium deficiency is considered to be very common and may affect 15 to 20 per cent of the population. It is common in those who eat diets high in processed foods, alcoholics, and in those with malabsorption problems.
Magnesium deficiency is especially prevalent in elderly people. This is due to low dietary intakes and also to the decreases in absorption and increases in excretion associated with aging.
Inadequate magnesium intake has been linked to several types of cardiovascular disease, including atherosclerosis, heart attack, angina, ischemic heart disease and cardiac arrhythmias. Epidemiological studies show that death rates from coronary heart disease are higher in areas where the water is low in magnesium. In a 1996 study, Swedish researchers investigated these links in 17 municipalities in the southern part of the country which had differing water magnesium concentrations. The study included 854 men who had died of heart attacks between the ages of 50 and 69, and 989 men of the same age in the same area who had died from cancer during the same time period. The results showed that men living in high magnesium water areas had a 35 per cent lower chance of death from heart attack than those who drank low magnesium water. The results of a 1997 study done in Taiwan suggest that magnesium in drinking water helps to prevent death from cerebrovascular disease.
Results from the Atherosclerosis Risk in Communities (ARIC) Study support the association between low serum and dietary magnesium, and various types of cardiovascular disease including high blood pressure. A total of 15,248 people took part, male and female, black and white, aged 45 to 64 years. The results showed that serum magnesium levels were significantly lower in participants with cardiovascular disease, high blood pressure, and diabetes than in those free of these diseases. Low dietary intake was linked to lower beneficial HDL cholesterol levels and thicker carotid artery walls, both of which increase the risk of cardiovascular disease.
Researchers involved in a 1996 study done in Wales found a trend towards protection from ischemic heart disease in men with high magnesium intakes.
However, when other factors were taken into account, the results did not appear to be significant. Magnesium deficiency is also linked to variant angina, a disorder in which coronary heart vessels go into spasm. A 1996 Japanese study found that men with lower magnesium levels had more frequent and severe angina attacks.7 Magnesium-deficient heart muscle is more vulnerable to lack of oxygen.
Magnesium deficiency may increase the risk of cardiovascular disease in several ways. Chronic magnesium deficiency in animals has been shown to result in microscopic changes in the heart arteries and the development of atherosclerosis. Deficiency also leads to changes in the heart muscle itself, including cell degeneration, fibrosis, necrosis and calcification. Blood fat levels are also affected by magnesium dietary intake. Cholesterol may be more susceptible to oxidative damage when magnesium levels are low. Some of the harmful effects of magnesium deficiency may be due to the products of increased fat oxidation.
Magnesium deficiency also contributes to cardiac arrhythmias, possibly because magnesium is responsible for maintaining potassium concentrations inside muscle cells. Potassium plays a role in heart muscle contraction. Magnesium deficiency has been implicated in mitral valve prolapse, a disorder in which the mitral valve in the heart fails to properly close off the heart chambers from each other during contraction. As many as 85 per cent of sufferers may have chronic magnesium deficiency.
High blood pressure
Results from the ARIC study mentioned above showed that low dietary intakes of magnesium are linked to higher diastolic and systolic blood pressures, possibly due to a reduction in the relaxing effect on blood vessels and by indirect effects on potassium balance. Studies suggest that around 30 per cent of high blood pressure sufferers consume inadequate amounts of magnesium and high blood pressure is more common in areas where the water is low in magnesium.
The Honolulu Heart Study, which looked at the relationship between dietary magnesium intake and blood pressure, found that those in the high intake group had, on average, systolic blood pressures 6.4 mmHg lower and diastolic pressures 3.1 mmHg lower than those in the low intake group.8 In another survey of over 58,000 women, researchers found that those with magnesium intakes of less than 200 mg per day had a significantly higher risk of developing high blood pressure than women whose intakes were over 300 mg per day.9 In another study published in 1992, researchers also found that low dietary intakes of magnesium were linked to an increased risk of high blood pressure in over 30,000 men.10
Magnesium deficiency results in impaired insulin secretion and reduces tissue sensitivity to insulin. Sub-clinical magnesium deficiency is common in diabetes and occurs because of insufficient magnesium intakes and increased magnesium losses, particularly in the urine. In Type II, or non-insulin-dependent, diabetes mellitus, magnesium deficiency seems to be associated with insulin resistance. It may also be involved in the development of diabetes complications and may contribute to the increased risk of sudden death associated with diabetes. Some studies suggest that magnesium deficiency may play a role in spontaneous abortion and birth defects in diabetic women.
Results from the ARIC study suggest that serum magnesium levels are low in those suffering from diabetes and that intake is related to insulin levels. Magnesium plays a role in the insulin-mediated uptake of glucose into cells, and deficiency may worsen control of diabetes. Low blood magnesium levels are commonly associated with many complications of diabetes, including heart disease and high blood pressure.
According to research presented at the 1997 annual meeting of the American Diabetes Association, low magnesium levels predict Type II diabetes in whites. Researchers from Johns Hopkins University Medical School examined blood levels of magnesium in over 12,000 nondiabetic, middle-aged African American and white subjects and monitored them for six years. No relationship was found between magnesium levels and diabetes in African Americans, but a relationship was seen in whites.
Magnesium is vital for normal bone function and deficiency may contribute to osteoporosis. In a 1995 study, results showed that women whose dietary intakes were less than 187 mg per day had a lower bone mineral density than women whose average intakes were more than 187 mg.
Magnesium is essential for the normal function of the parathyroid glands, metabolism of vitamin D, and adequate sensitivity of bone to parathyroid hormone and vitamin D. Magnesium deficiency may impair vitamin D metaboUsm which adversely affects bone-building. Magnesium deficiency is also known to cause resistance to parathyroid hormone action which affects calcium balance and may cause abnormal bone formation. However, magnesium excess inhibits parathyroid hormone secretion which means that bone metabolism is impaired under positive as well as under negative magnesium balance. Maintaining normal calcium-to-magnesium balance is very important in the prevention of osteoporosis.
Magnesium metabolism appears to be altered in some migraine sufferers and deficiency may contribute to symptoms through effects on neurotransmitters and blood vessels, and muscles in the head and neck.
Red blood cell concentrations of magnesium appear to be low in women with premenstrual syndrome. The calcium to magnesium ratio also seems to be affected by hormonal fluctuations which may affect neurotransmitter levels and lead to premenstrual symptoms.
Epidemiological evidence suggests that a low intake of magnesium is associated with impaired lung function, bronchial hyperreactivity and wheezing.
Magnesium deficiency leads to kidney stones in animal studies. Magnesium inhibits the precipitation of calcium phosphate and calcium oxalate, two substances which contribute to the formation of kidney stones.
Magnesium deficiency occurs early in the course of HIV infection. This may be relevant to the HIV-related symptoms of fatigue, lethargy and mental impairment.
Lack of magnesium decreases energy efficiency, and research has shown that people who are deficient in magnesium may use more energy during exercise. In a recent study, USDA researchers investigated the amount of oxygen needed by healthy women over 50 to perform a certain amount of low intensity work on an exercise bicycle. When their dietary magnesium was inadequate (150 mg daily) they used 10 to 15 per cent more oxygen to perform the work and their heart rates climbed by about 10 beats per minute. The results suggest that magnesium deficiency is associated with increased physiological demands to do the same amount of work as when magnesium is adequate.
In a 1998 study, researchers from the University of Texas examined body magnesium concentrations in 26 marathon runners during an endurance run. They found that levels in the muscles and urine dropped significantly, possibly putting the athletes at risk of decreased performance and muscle cramps.
Magnesium deficiency may also play a role in pre-eclampsia and eclampsia (toxemia of pregnancy), leg cramps, sleeping problems, Candida albicans infection, gastric cancer, allergies, chronic fatigue syndrome and anxiety. Low blood levels of magnesium are also sometimes found in bulimia nervosa sufferers and patients with irritable bowel syndrome.
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