BY DR YEAP SWAN SIM
Some questions have arisen about the benefits of calcium after certain studies reported a link with heart attacks.
Take note that for calcium tablets taken as supplements, the label usually gives the total amount of calcium salt in the tablet, not its elemental calcium content. -MCT
CALCIUM is an important mineral that can be found in many foods. The body needs calcium to maintain strong bones and carry out important functions with regards to muscle and nerve function.
Approximately 99% of the body’s calcium is stored in bones and teeth. Thus, it makes intuitive sense that adequate calcium is required for optimal bone health.
How much calcium is enough?
The Health Ministry recommends that adolescents (10-18 years old) should have a calcium intake of 1,000mg daily. Pregnant and lactating mothers should also take 1,000mg of calcium daily.
Men and women between the ages of 19 and 40 years are advised to have an intake of 800mg calcium daily, and those over the age of 50 years, 1,000mg calcium daily.
All these recommendations are based on elemental calcium intake, and should include both dietary and supplemental calcium.
In Malaysia, the average calcium intake from the diet is about 500mg daily.
The situation is slightly different for calcium tablets taken as supplements. The tablets usually give the total amount of calcium salt in the tablet. For example, one tablet of calcium carbonate is commonly 500mg. In effect, the amount of elemental calcium in that tablet is 40% of 500mg, which is only 200mg.
Calcium lactate, another common calcium supplement, comes in 300mg tablets. But it only contains 13% of elemental calcium, so a 300mg tablet of calcium lactate only contains 39mg of elemental calcium.
Some proprietary brands of calcium carbonate will have 1,500mg in a single tablet, giving 600mg elemental calcium per tablet.
Thus, when buying any calcium supplement, please check its formulation, as this would affect the amount of calcium you get per tablet.
For optimal absorption, the amount of elemental calcium should not exceed 500-600mg per dose, irrespective of the calcium preparation. If you require more than 600mg of calcium supplement daily, the dose should be divided.
Does taking calcium supplements lead to heart attacks?
The short answer is that we are not sure. The bad news about calcium started in 2008 when a study from New Zealand showed that postmenopausal women taking 1,000mg of elemental calcium daily were more likely to have a heart attack (4.92%), compared to those on placebo (2.84%).
However, the researchers will usually report the figures as relative risk, i.e. comparing the ratio of the probability of the event occurring in one study group versus the other group.
If we do that, then the relative risk for having a heart attack while on calcium is 1.49, i.e. 49% more than the other group.
If put this way, the results seem worrying, but the absolute numbers of affected individuals are small.
This stirred up a storm, since calcium has always been considered a beneficial mineral.
The controversy led to more studies on the same topic from other parts of the world, which did not show the same results.
Three studies – one each from Australia, Scotland and Canada – showed no increased cardiovascular mortality in subjects taking about 1,000mg elemental calcium supplements daily, compared to those who did not; one of the studies had followed up the subjects for as long as 10 years.
Another study, this one a meta-analysis (a type of study combining the results from many smaller studies to try to get a better understanding of the size of the effect of an intervention), showed that 2.71% of the subjects taking more than 1,000mg of calcium supplementation daily had a heart attack, compared to 2.24% of those on placebo.
The relative risk between the groups was 1.27 in this study.
A study from Europe with almost 24,000 subjects followed up for an average of 11 years, showed no difference in heart attack incidence between those taking lower, compared to higher levels of dietary calcium. However, the same study showed that there were more heart attacks in those taking calcium supplements.
A caveat to all this information is that all these studies were done in Caucasian populations where the average dietary calcium intake was already nearly 1,000mg daily, so the supplements further increased the average calcium intake to anywhere between 1,500 and 2,000mg daily.
Whether calcium supplementation can lead to similar problems in a low dietary calcium intake population such as in Malaysia is not known.
However, the reassuring news is that no such effect was seen with increased dietary calcium intake, so it is advisable to take calcium from food sources in the diet, rather than as a supplemental tablet.
Calcium and osteoporosis
Osteoporosis is a condition where the bones are more fragile, and thus, more prone to breaks or fractures. It occurs when the bones lose minerals, especially calcium, which leads to low bone density.
In patients who have confirmed osteoporosis, diagnosed either by a dual-energy X-ray absorptiometry (DXA) scan or following an osteo-porotic fracture, treatment with medication is advised.
Just taking calcium supplements (with or without vitamin D) alone at this stage is not helpful in increasing bone density.
All the trials of the medications for osteoporosis, such as the bisphosphonates, strontium, or teriparatide, have been done with calcium and vitamin D given to all patients.
The patients in the comparison group taking the placebo treatment are therefore effectively only taking calcium and vitamin D.
Inevitably, this group of patients will lose, or at best maintain, bone density over the period of the study.
The treatment arm taking the active drug and calcium and vitamin D would usually show an improvement in their bone density.
So, the efficacy of osteoporotic treatments has always been assessed with the patients taking calcium (typically between 500 and 1,000mg of calcium carbonate daily) and vitamin D, and it is not known whether the treatment will be slightly less effective without adequate calcium and vitamin D supplementation.
In addition, these treatment studies have been done in European or North American patients whose average dietary calcium intakes are typically 800-1,000mg daily, which is double the average Malaysian dietary calcium intake.
So, what can we conclude? In Malaysia, the average dietary calcium intake is still low, approximately 500mg daily.
Adolescents still building their bones to their peak bone mass should definitely be encouraged to take up to 1,000mg of calcium daily, preferably from calcium-rich foods.
If you are a healthy postmenopausal woman, you should try to maintain a calcium intake of approximately 1,000mg daily, both from food and supplements.
If you already have osteoporosis, please discuss with your doctor what would be the best medication for your condition. In addition, an adequate calcium and vitamin D intake is recommended, again aiming for a total intake of 1,000mg calcium daily, both from the diet and supplements, together with 800IU of vitamin D daily.
References:
1. National Coordinating Committee on Food and Nutrition (2005). Recommended Nutrient Intakes for Malaysia. Ministry of Health, Malaysia.
2. Bolland MJ, Barber PA, Doughty RN, et al. Vascular events in healthy older women receiving calcium supplementation: randomised controlled trial. BMJ 2008; 336(7638): 262-6.
3. Lewis JR, Calver J, Zhu K, et al. Calcium supplementation and the risks of atherosclerotic vascular disease in older women: results of a 5-year RCT and a 4.5-year follow-up. J Bone Miner Res 2011; 26: 35–41.
4. Avenell A, MacLennan GS, Jenkinson DJ, et al. Long-Term Follow-Up for Mortality and Cancer in a Randomised Placebo-Controlled Trial of Vitamin D3 and/or Calcium (RECORD Trial). J Clin Endocrinol Metab 2013; 97: 614–22.
5. Langsetmo L, Berger C, Kreiger N, et al. Calcium and Vitamin D Intake and Mortality: Results from the Canadian Multicentre Osteoporosis Study (CaMos). J Clin Endocrinol Metab 2013; 98: 3010-8.
6. Bolland MJ, Avenell A, Baron JA, et al. Effect of calcium supplements on risk of myocardial infarction and cardiovascular events: meta-analysis. BMJ 2010; 341: c3691. doi:10.1136/bmj.c3691.
