Are calcium supplements harming your heart more than they are benefiting your bones? Recent studies have thrown up some disturbing findings. By Michael Lim

WHEN we watch TV, listen to the radio, or visit supermarkets and pharmacies, we are almost certainly assailed by advertisements advising us to take calcium supplements or milk with high calcium to strengthen our bones. The common belief is that taking calcium is good for us, but recent studies suggest that we need to re-examine this issue more carefully as evidence is emerging that calcium intake may increase the risk of heart attacks in older women.

In my years of seeing thousands of patients who had their heart arteries assessed, what was obvious was that almost all those with significant blockage of their heart arteries had calcium deposits (plaques) in the narrowed segments. One particular incident stuck in my mind. Two sisters who did not differ much in age and risk factors for heart disease had very different heart arteries when they saw me. The sister who had been taking calcium tablets for several years had extensive calcification of her heart arteries while her sister who had not taken any calcium tablets did not have any calcification in her heart arteries.

An epidemiological study suggests that arterial disease is the leading cause of death in countries that have high daily calcium intakes and that there is a low prevalence of death from arterial diseases in countries with low calcium intakes.

In the past 20 years, the CT (computed tomography) scan has been used to measure the amount of calcium in the heart arteries. This is measured by a scoring system called the Agatston Score which refers to the amount of calcium based upon the size and the density of the calcified plaques in the heart arteries.

Absolute Agatston scores of more than 400 denote extensive amounts of calcification. It is well established that individuals with Agatston Scores above 400 have an increased incidence of procedures for narrowed heart artery (such as heart bypass surgery or opening of heart arteries with balloon and stents), heart attacks and death within two to five years after undergoing a coronary artery calcification assessment. Individuals with very high Agatston scores of over 1,000 have a 20 per cent chance of suffering a heart attack or death from heart disease within a year. Studies show that calcification of heart arteries was present in 95 per cent of those who had a first-time heart attack compared to slightly over half in the control group. While calcium deposits in heart arteries are associated with blockage of heart arteries, they also have other detrimental effects such as stiffening of the arteries and affecting valve function.

Calcium and the heart

Despite the known association between calcium deposits in the heart arteries and heart attacks, data has only recently been published on analyses of multiple calcium intake studies. These suggest that taking calcium supplements was associated with about a 30 per cent increase in the risk of heart attack and a smaller, non-significant, increase in the risk of stroke and mortality. While many brands of calcium will have you believe that they have advantages over other brands, the authors reported that the findings were not only independent of age and sex, but also of the type of supplement. While the increase in the risk of heart attacks is modest in the study, the widespread consumption of calcium tablets may potentially result in large numbers of individuals developing heart attacks.

Time to stop your supplements?

Experts have advised that given the current findings and the limited evidence and modest benefits of calcium supplements on bone density and fracture prevention, a reassessment of the role of calcium supplements in osteoporosis management is warranted. As there are also doubts about the efficacy of calcium supplements in reducing fractures, these experts have advised that patients with osteoporosis should generally not be treated with calcium supplements, either alone or in combination with vitamin D, unless they are also receiving an effective treatment for osteoporosis for a clinically accepted indication. What this means is that for the large majority who do not have osteoporosis, the need for daily calcium supplementation has to be carefully reassessed.

We need calcium not only for our bones but for other body functions as well. However, even experts cannot agree on how much calcium is required to keep the bones healthy. While the World Health Organization suggests that 400 to 500 milligrams (mg) of calcium a day are needed to prevent osteoporosis, the American Institute of Medicine recommendation is 1,000 mg/day from the ages 19 to 50 and 1,200 mg/day after that. While there is no agreement on what the ideal average calcium intake should be, there is no disagreement that excessive calcium intake is harmful.

While the studies suggest that oral calcium supplementation is associated with heart disease, there is as yet no current evidence to suggest that dietary sources of calcium have any adverse impact on the heart. Given the current uncertainties about the benefits of calcium supplementation, dietary sources of calcium and non-calcium supplementation measures for strengthening bones should be considered. Simple weight-bearing exercises like walking and running are beneficial for your bones. Getting vitamin D through 10 to 15 minutes of sunshine daily is also beneficial for bones and this is definitely not difficult in this tropical climate where there is sunshine all year round. For those who are averse to sunshine, salmon, tuna, sardines and milk are ready sources of vitamin D.

In summary, there is definite and strong evidence that increasing calcification of heart arteries is significantly associated with an increased risk of heart attacks and death. Recent studies suggest that oral calcium supplementation is associated with a higher risk of heart attack. Given the results of these studies, the limited evidence that calcium supplementation is beneficial for osteoporosis and doubts on the efficacy of calcium supplementation in reducing fractures, there is a need to reassess the role of calcium supplementation. While calcium is required for the body, disagreement on the optimal amount of calcium intake remains. More research studies will be required to ascertain the optimal calcium intake that will be beneficial for the body without increasing the risk of heart attacks or strokes.