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MAGNESIUM and CARDIOVASCULAR DISEASE

Abstract:  Available research suggests that a health-interested person should include about 450 mg per day of magnesium in diet to reduce risk of heart disease .  A supplement of about 200 mg per day will be prudent to offset probable amounts of about 300 mg/day in the foods of many diets.  Life Ahead now includes a conservative minimum risk factor for heart disease of 0.75 for 200 mg/day of magnesium with limits on minimum and maximum risks accepted.  This is a smaller risk than that actually measured.  It seems likely that this benefit is achieved via mechanisms other than that of an antioxidant.  No benefits for stroke or cancer are now confirmed for use of magnesium.

Magnesium and Heart Disease:  Results of three useful observation studies and one clinical study found relating dietary Magnesium to Heart Disease are shown in Table M.  These all show that added dietary Magnesium reduces risk of heart disease appreciably.  An average risk ratio of 0.66 is obtained from the observation study comparisons, all are statistically consistent, and all but one of these is individually significant well above the 95% level.  The risk ratio obtained in the clinical study for a much larger amount of Magnesium is similar at about 0.60.  This research confirms benefits for the mineral in both foods and supplements, and that this improvement in risk probably results from intermediate or short term exposure.  

The mechanism by which Magnesium produces these benefits is not clear. Correlations relating population heart disease to Magnesium in drinking water have been noted. Magnesium can reduce hypertension somewhat, but this effect is far too small to explain the moderate reductions of risk of coronary heart disease found.  All observation studies included probable durations of Magnesium exposure for long periods of time that were more than adequate to confirm a possible effect from reducing atherosclerosis.  But Magnesium has been indicated to have both antioxidant and anti-clotting properties.  The benefit from the clinical study of 0.60 risk ratio from what was a mean duration of 5 years exposure suggests that Magnesium may operate over shorter time duration than that needed for benefit from antioxidants.

A key problem in including Magnesium as an added factor in Life Ahead is:  “If this is another antioxidant, its benefit as an individual factor may not add to the overall benefits obtainable from a recommended total use of other Vitamins and Selenium.”  No research on this appears to have been done.  The rather substantial effect found in the clinical study, however, is larger than would be obtained from other antioxidants over this 5 year duration of time. Thus best evidence now is that magnesium does contribute some added benefit beyond its value as an antioxidant. 

Thus with recognition of a need for some conservatism, Life Ahead now includes a benefit to heart disease for use of Magnesium as a risk benefit of 0.75 for a difference of 200 mg/day use of total Magnesium intake. This acknowledges only about half of the benefit found from the available research in Table M. This recognizes that benefits from Magnesium may partly duplicate those from other nutrients and supplements.  Because of a lack of data on duration of exposure, its effect is now included in Life Ahead as a direct association starting from an initial exposure that is assumed to start at ten years before present age.  Life Ahead assumes that an average diet includes 300 mg/day, and acknowledges an increased risk for a deficiency of up to 150 mg/day, and a decreased risk for amounts up to a maximum of 450 mg/day.

Magnesium and Stroke:  Studies #5 and #6 measure the benefit of Magnesium on risk of Stroke.  The average of the few risk ratios included suggests a small benefit to risk of about 0.8.  Although these research studies are the largest and most important studies of their kind, there are questions - and these were raised by the researchers - as to whether or not this benefit is valid. Study #5 showed that essentially all of the measured benefit was for men with elevated blood pressure.  Most health interested persons today with high blood pressure presumably would be taking drugs to offset a blood pressure problem.  Thus this benefit might not accrue either to them or to those with normal blood pressure.

Also, there was extensive confounding of levels of magnesium with fiber and potassium in Study #5, and with calcium in Study #6.  Correction for these factors eliminated the benefits estimated.  Considering these questions, and the usual need for at least three confirming studies on any factor inclusion in Life Ahead, no effect of Magnesium on Stroke is now included in the program.

No useful studies measuring the effect of dietary Magnesium on risk of Cancer were found.

The likely benefit to heart disease should be sufficient to encourage any health interested person to include a total of about 450 mg per day of Magnesium in dietary intake.  This can be obtained via strategic use of foods, but can be better assured with a daily supplement of at least 200-300 mg.  A typical Magnesium intake from diet is about 300 mg/day.  Supplements of 500 mg. or less are considered to cause no negative problem.  Other benefits not now valued in Life Ahead have been suggested for use of Magnesium. These include some lowering of blood pressure, somewhat lower risk of diabetes, slowing of osteoporosis, and as a help in maintaining steady heart beats.

Magnesium has been found in small studies to benefit blood pressure, inhibit migraine headaches, prevent leg cramps and benefit other secondary problems.