If you are one of the five million or so people in the UK taking a calcium supplement then you are likely to have been worried by new research linking the supplements to stroke and heart attack. So is there any truth in recent press reports that “they do more harm than good”?

Calcium is one of the key building blocks of healthy bones and a deficiency of the mineral – something that is more common as we get older due to a combination of poor dietary intake and reduced absorption – can hasten the natural weakening process that occurs in most of our bones as we age. Calcium supplements, often taken along with vitamin D to boost absorption, can slow this process and offer some protection against the bone thinning disease osteoporosis, and resulting fractures.

This modest protective effect is the rationale behind the widespread use of calcium supplements – either prescribed or over-the-counter – but there is growing evidence that any resulting increase in bone strength comes at a price. It has been known for some time that high dose supplements can cause side effects like constipation and an increased risk of kidney stones, but the latest concerns centre on a link with stroke and heart attack.

A recent review of the evidence published in the medical journal Heart suggests that women taking calcium supplements are just over 20% more likely to have a heart attack and 15% more likely to have a stroke than those who don’t take supplements. And, to put the pros and cons in perspective, the same review estimates that treating a group of a thousand older adults with calcium supplements for five years is likely to result in 14 more heart attacks, 10 more strokes and 13 more deaths, balanced against 26 fewer broken hips and other bones.

But not all experts agree that the case against supplementation is quite so clear-cut. Indeed even the Medicines and Healthcare products Regulatory Authority does not seem that convinced, referring to a “possible modest increase in the risk of some cardiovascular events” in people taking calcium and vitamin D supplements and advising “no change to prescribing practice is currently recommended”.

Experts I have spoken with agree more research is needed to confirm the link, but I detect a growing sense of unease with the current size one-size fits all approach to supplementation – an approach which can result in some people easily consuming 1500mg of calcium a day, more than twice the current recommended daily intake.

It is unclear why calcium might increase the risk of stroke and heart attack, but it could be caused by the sudden rise in blood calcium levels seen after taking a high dose supplement – a rise that may accelerate calcification of the lining of arteries and increase the “stickiness” of blood.

A high dietary intake from natural sources (see above) is not associated with this type of rapid rise in blood levels so it makes sense to try and get your calcium naturally (and slowly) through diet rather than depend on pills, and to only use the latter to make up any shortfall in your diet.

If you are concerned about your bones, or are already on treatment for osteoporosis, then a sensible way forward would be to take in a minimum of 700mg of calcium a day, and if you can’t achieve this through diet alone, then supplement accordingly, aiming for a total of somewhere between 700 – 1000mg a day (commonly used supplements contain 500-600mg in each tablet).

It is essential to have vitamin D to make good use of the calcium so either take a combination supplement, or take vitamin D separately (current guidelines for adults recommend everyone over the age of 65 should take a vitamin D supplement, along with pregnant and breastfeeding women, and anyone who doesn’t spend much time outside).

In practice this type of approach to calcium intake will probably mean some people don’t need supplementation at all, while others can get away with taking much lower doses. Only time will tell whether this proves to be any safer, but common sense suggests it might.


• The average human body contains 1kg of calcium, 99% of which is found in the teeth and bones

• Adults require a minimum of 700mg of calcium a day for optimal bone health – easily achievable through diet for most people

• 100mls of semi-skimmed milk contains 120mg of calcium, 50g of Cheddar has 370mg, and 100g of whitebait contains 860mg

• Too much caffeine and salt in your diet reduce calcium absorption

• For more detailed advice on boosting your calcium intake naturally, and advice on supplements, visit www.nos.org.uk