When it comes to calcium and osteoporosis, everyone is
agreed – NDs, MDs, acupuncturists, NPs, and chiropractors all recommend 1200 mg
of calcium a day to help ward off the onset of osteoporosis. By contrast,
there’s not as much discussion of magnesium when it comes to high blood
pressure, despite an overwhelming amount of research into the topic, a fact at
least partly explainable by inconsistent results in clinical studies. This
week, I’m going to write on this topic, referencing select articles from the
medical literature – there are thousands of articles on the topic of magnesium
and hypertension, and it’s easy to get lost in the sea of literature.
Let me start by discussing briefly the epidemiological
information on the topic. I won’t present studies here, though there are many,
but in general, the research indicates that people who consume higher amounts
of magnesium have, in general, a lower prevalence of hypertension, lower blood
pressure in general, and lower incidence of stroke. Of course there are studies
that have found no association, as is the case when you have enough studies
devoted to a given topic, but a greater number of studies indicate that there
is a relationship present, and the evidence is quite compelling.
One of the reasons that I’m inclined to believe the link is
because there exist plausible mechanisms for magnesium’s ability to reduce
blood pressure. A recent article published in the Journal of Clinical
Hypertension elaborates on the biochemistry behind magnesium’s role in hypertension, indicating multiple pathways by which it acts to lower blood
pressure, but primarily likening its action to that of a calcium channel
blocker (a class of medication used for hypertension and chronic heart
failure). Much like a calcium channel blocker, magnesium induces vasodilatation
of arteries and regulates cardiac contractility, thus lowering blood pressure
and improving the function of the heart. It’s also been suggested that the role
that magnesium plays in reducing blood pressure is in part due to the action
its presence exerts on other minerals in the body, including sodium, potassium
and calcium.
As always, none of this should be taken without evidence
that it actually lowers blood pressure in a clinical setting. A 2002
meta-analysis, which looked at 22 trials, including 1220 patients, found that
magnesium provided mild benefit to hypertensive patients, although this benefit
was dose-dependent, which suggests that greater benefit might be derived from
higher doses of magnesium. Since then, further studies have been published that
indicate benefit, albeit mild, from magnesium supplementation (1, 2). Taken together,
these studies indicate that there is some benefit to be had from magnesium in
regards to hypertension. However, all authors more or less agree that the
benefit is somewhat inconsistent in clinical trials. The authors of the
previously mentioned meta-analysis indicated that small studies and variable
study design was a likely factor in the inconsistencies, and called for larger
studies in order to more clearly define the benefit and role of magnesium in
hypertension.
One piece of the puzzle that has as yet not been fully
fleshed out, but which I believe is likely to answer many questions is that of
magnesium deficiency. As early as 1983, a study published in the British
Medical Journal showed that magnesium could reduce blood pressure significantly, and postulated that it was due to a correction of magnesium
deficiency. However, this hasn’t been a major area of research in the
intervening period, although a recent study showed that magnesium did produce
surprisingly large decreases in blood pressure among a collection of
hypertensive diabetics who also had low serum magnesium. This piece of
information may give us clinical guidelines regarding when to prescribe
magnesium for hypertension, and when to resort to other measures. There’s been
some dispute in the past as to the best way to measure a patient’s magnesium
status, but I think the clinical correlation here points the way forward.
So what’s the take home message? In all, magnesium does
appear to provide some mild benefit in cases of hypertension, a benefit even
more marked if the patient is demonstrably low in magnesium. As always, be in
consultation with a healthcare provider about using nutritional supplements to
help combat disease, especially one with consequences as serious as
hypertension – additionally, magnesium is not without side effects, and it
takes an experienced provider to help guide you through that.
