Magnesiummmmmmmm

Thanks to those who sent in comments extolling the benefits of adding magnesium to my diet; which immediately sent me looking for various articles about this mineral and it's potential health benefits. This, from the Linus Pauling Institute at Oregon State University, goes into more detail about magnesium and health:


Hypertension (high blood pressure)


Large epidemiological studies suggest a relationship between magnesium and blood pressure. However, the fact that foods high in magnesium (fruits, vegetables, whole grains) are frequently high in potassium and dietary fiber has made it difficult to evaluate independent effects of magnesium on blood pressure. A prospective cohort study of more than 30,000 male health professionals found an inverse association between dietary fiber, potassium, and magnesium, and the development of hypertension over a four-year period (6). In a similar study of more than 40,000 female registered nurses, dietary fiber and dietary magnesium were each inversely associated with systolic and diastolic blood pressures in those who did not develop hypertension over the four-year study period, but neither dietary fiber nor magnesium was related to the risk of developing hypertension (7). The Atherosclerosis Risk in Communities (ARIC) study examined dietary magnesium intake, magnesium blood levels, and risk of developing hypertension in 7,731 men and women over a six-year period (8). The risk of developing hypertension in both men and women decreased as serum magnesium levels increased, but the trend was only statistically significant in women. Although the investigators found no association between dietary magnesium and the incidence of hypertension, they suggested that low serum magnesium levels may play a modest role in the development of hypertension.


Cardiovascular disease


A number of studies have found decreased mortality from cardiovascular diseases in populations who routinely consume "hard" water. Hard (alkaline) water is generally high in magnesium but may also contain more calcium and fluoride than "soft" water, making the cardioprotective effects of hard water difficult to attribute to magnesium alone (9). One large prospective study (almost 14,000 men and women) found a significant trend for increasing serum magnesium levels to be associated with decreased risk of coronary heart disease in women but not in men (10). However, the risk of coronary heart disease in the lowest quartile of dietary magnesium intake was not significantly higher than the risk in the highest quartile in men or women. Additionally, a large prospective study in over 35,000 women reported that dietary magnesium, assessed by food frequency questionairre, was not associated with risk for various cardiovascular diseases, including stroke, nonfatal myocardial infarction, and coronary heart disease (11). Presently, the relationship between dietary magnesium intake and the risk of cardiovascular disease remains unclear.


Osteoporosis


Although decreased bone mineral density (BMD) is the primary feature of osteoporosis, other osteoporotic changes in the collagenous matrix and mineral components of bone may result in bones that are brittle and more susceptible to fracture. Magnesium comprises about 1% of bone mineral and is known to influence both bone matrix and bone mineral metabolism. As the magnesium content of bone mineral decreases, bone crystals become larger and more brittle. Some studies have found lower magnesium content and larger bone crystals in bones of osteoporotic women compared to non-osteoporotic controls (12). Inadequate serum magnesium levels are known to result in low serum calcium levels, resistance to parathyroid hormone action, and resistance to some of the effects of vitamin D, all of which can lead to increased bone loss (see Calcium). A study of over 900 elderly men and women found higher dietary magnesium intakes were associated with increased bone mineral density at the hip in both men and women. However, because magnesium and potassium are present in many of the same foods, the effect of dietary magnesium could not be isolated (13). More recently, a study in over 2,000 elderly individuals reported that magnesium intake was positively associated with total-body BMD in white men and women but not in black men and women (14). Few studies have addressed the effect of magnesium supplementation on bone mineral density or osteoporosis in humans. In a small group of postmenopausal women with osteoporosis, magnesium supplementation of 750 mg/day for the first six months followed by 250 mg/day for 18 more months resulted in increased BMD at the wrist after one year, with no further increase after two years of supplementation (15). A study in postmenopausal women who were taking estrogen replacement therapy and also a multivitamin found that supplementation with an additional 500 mg/day of magnesium and 600 mg/day of calcium resulted in increased BMD at the heel compared to postmenopausal women receiving only estrogen replacement therapy (16). Presently, the potential for increased magnesium intake to influence calcium and bone metabolism warrants more research with particular attention to its role in the prevention and treatment of osteoporosis.


The National Institutes of Health also has a very good magnesium dietary supplement fact sheet:


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].

The NIH fact sheet goes on to elaborate further in identifying the best food sources of magnesium, information about supplementing magnesium and best bioavailable forms of magnesium, signs of low magnesium, and also, importantly, signs of high magnesium due to mis-use of antacids and magnesium supplements:

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.


I guess the message here is dietary magnesium is a very, very good thing and impossible to overdose. BUT supplementation, while potentially beneficial, must be monitored. So how much magnesium is safe to take as a supplement?


Linus Pauling Institute Recommendation


The Linus Pauling Institute supports the latest RDA for magnesium intake (420 mg/day for men over 30 years of age and 320 mg/day for women over 30 years of age). Following the Linus Pauling Institute recommendation to take a daily multivitamin/multimineral supplement will ensure an intake of at least 100 mg of magnesium/day. Few multivitamin/multimineral supplements contain more than 100 mg of magnesium due to its bulk. Because magnesium is plentiful in foods, eating a varied diet that provides green vegetables and whole grains daily should provide the rest of an individual's magnesium requirement.


Older adults (65 years and older)


Older adults are less likely than younger adults to consume enough magnesium to meet their needs and should therefore take care to eat magnesium-rich foods in addition to taking a multivitamin-mineral supplement daily. Because older adults are more likely to have impaired kidney function, they should avoid taking more than 350 mg/day of supplemental magnesium without medical consultation.

Interesting. Thanks for the info., guys.