Does calcium cause heart attacks?

A recent study was published in the British Medical Journal stating that taking calcium supplements increases a person’s risk of myocardial infarction and other cardiovascular events, in other words, heart attack and stroke. (Bolland, Avenell, Baron, Grey, MacLennan, Gamble & Reid, 2010)

As I prescribe calcium supplements for many of my patients, so you can understand that this was rather alarming research for me to come across.  I decided to go to the source of the information and read the original article only to discover that it is science’s own methodology that has contributed to this outcome.

A little info on calcium:

Calcium is a very important mineral.  It is found predominantly in the body’s skeleton, and some in the blood stream.  It provides strength to the bones along with other minerals such as magnesium, boron, manganese, and silica.  However its function in the bones is also as storage, to ensure the nervous system, and thus the blood stream, has a constant supply.  Calcium is used in muscle contractions and nerve impulses, and regulates the permeability of cell membranes, which means it helps nutrients get in and out of cells easily.  It is used all over the body in pretty much every cell.

The body is very good at ensuring that it has constant supplies of important minerals, so that is why it stores calcium in the bones.  This is an insurance policy against times when a person’s diet may be low in calcium. Unfortunately the modern diet is moderately low in calcium, and other factors such as high intake of fizzy drinks, alcohol, caffeine, and smoking, all lead to a low absorption of calcium, as does low oestrogen levels such as with menopausal women.

Too little calcium in the blood leads to many things, some of which are; muscle spasms and twitches, irregular heart beat, and high blood pressure.  Too little calcium in the bones leads to osteoporosis and is a sign that the person has not had an adequate calcium intake for a number of years.  More than 2 million Australians have osteoporosis and more than one million fractures occur each year because of it. (Sambrook, Seeman, Phillips, Ebeling, 2002)  It is no wonder that many naturopaths prescribe calcium to their patients.  Conversely, it is very rare to have too much calcium in the blood, however one of the effects of too much in the blood interestingly, is also high blood pressure.

So this takes us back to the original research, a meta-analysis of 13 studies that were randomised, double blind and placebo controlled.  This is the gold standard of scientific research. Research needs to have 2 study groups which are the same, change one thing about one group, in this case it is a calcium supplement, and then any differences seen between the groups can be only due to calcium.

Unfortunately it is the gold standard that is the issue in this research.  By including only studies that supplemented with high dose calcium, they have excluded the very supplements that naturopaths routinely prescribe, and more importantly, the very supplements that people who need calcium should take.

What does this mean for naturopathic supplements?

All naturopathic calcium supplements contain magnesium, and a host of other minerals to help the absorption of calcium.  This is the way calcium is found in food – it is never in isolation.  Magnesium in particular is an extremely important mineral to be given along side calcium.  In fact it should be given in a 2:1 ratio calcium to magnesium.  The amount of calcium used in the studies was over 500mg of elemental calcium per person, which is very high on its own with no magnesium to balance it out.  Magnesium regulates calcium metabolism and ensures that calcium is balanced in the body.  If there is a disproportionate excess of calcium, this can lead to a deficiency of magnesium as too much calcium can block magnesium absorption.  This situation could have been created in these studies.

Magnesium regulates heart function by helping the heart muscle to contract and relax effectively.  If a person is deficient in magnesium then the heart wont be able to beat properly and in some cases can lead to muscle spasms, and palpitations. Magnesium also helps the blood vessels to relax and leads to lowered blood pressure.  So in a person who has other factors that may contribute to a heart attack or stroke, such as high blood fats, high blood pressure, and atherosclerosis (hardening of the arteries), and lifestyle factors such as lack of exercise, poor diet, and smoking, then the influx of calcium and lack of magnesium could have lead to a heart attack or stroke.  However it is very important to note that this is a situation that has been artificially created by the research studies.

If you are taking a calcium supplement that has been prescribed by a naturopath, it will have magnesium in it as well, and will be safe for you to take.  If not, swap to a supplement that also has magnesium and other minerals in it.  If you have any questions about calcium supplementation, or calcium in the diet, then please just ask me. Leave any questions or comments below so that everyone can learn more about this important topic.



Bolland MJ, Avenell A, Baron JA, Grey A, MacLennan GS, Gamble GD, Reid IR. (2010) Effect of calcium supplements on risk of myocardial infarction and cardiovascular events: metal-analysis BMJ 341:c3691

Sambrook PN, Seeman E, Phillips SR, Ebeling PR. (2002) Preventing osteoporosis: outcomes of the Australian Fracture Prevention Summit. Med J Aust 176 Suppl:S1.

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