Do Calcium Supplements Increase Cardiovascular Risks - Research Paper Example

First Last 4 September Do calcium supplements increase cardiovascular risks? Cardiovascular diseases(CVD) are the leading cause of deaths worldwide. Seven million people each year dies of coronary heart diseases, while stroke kills nearly 6 million. It is characterized by damage to the heart, blood vessels and other parts of the cardiac system by genetic or acquired factors. [1] Cardiovascular defects such as malformation of heart structure, holes in the heart, abnormal valves, or abnormal heart chambers could exist at births. When the condition is present at birth, they are referred to as congenital heart disease. These may be caused by one or combination of these factors: genetic, maternal alcohol use, medicines used by expectant mother, etc. Congenital heart disease only constitute to a smaller portion of the fatality through CVD. Approximately 75% of the cases of CVD are caused by acquired factors such as poor lifestyle such as tobacco use, low fruit and vegetable diet, obesity, lack of physical activity, and high cholesterol intakes. [1] Several risk factors have been shown to cause CVD. Higher risks of acquiring of CVD occur in people above the age of 55 and the risk of stroke doubles every decade after. Gender is also a risk factor. Higher rates of coronary heart disease and stroke were seen in men compared to women. [1] One of the prevailing causes of deaths from CVD is myocardial infarction. Myocardial infarction, more commonly known as heart attack is caused by interruption of blood supply to the heart causing the cardiac cells to die (myocardial necrosis). It is often caused by blockage due to cholesterol or other deposits. Myocardial infarction can be characterized by: (i) sudden, unexpected cardiac death, involving cardiac arrest; (ii) detection of rise and/or fall of cardiac biomarkers preferably troponin; (iii) pathological findings of an acute myocardial infarction. [2] Calcium is an essential mineral for numerous body processes. It is found in great abundance in the body, majority of which is in the bones and teeth, and a small percentage is found in the blood. It is an essential element for nerve conduction, muscle contraction and blood clotting. The Food and Nutrition Board recommends daily dietary allowance of calcium at 1,000 mg, with increased intake of 1,200 to 1,300mg for adolescents (9 to 18 years old) and pregnant and postmenopausal women. [3] Natural sources of calcium include milk, yogurt and cheese. However, due to increased demand for calcium in several age groups, some people are being advised on taking supplements. Calcium supplements are also given as prevention to osteoporosis. Vitamin D is usually added to the supplements because vitamin D is converted to a hormone in the body which synthesizes the proteins needed for proper calcium absorption. [3] Calcium has been proposed to reduce cardiovascular risks by decreasing intestinal absorption of lipids. [3] However, recent controversial clinical studies and meta-analysis suggests otherwise. Now, the question is: Do calcium supplements induce the risks of acquiring CVD? The Women’s Health Initiative Calcium / Vitamin D Supplementation (WHI CaD) study team lead by Dr. Judith Hsia said there is no relationship between the two. [4] In 2007, the team tested the effect of calcium and vitamin D supplement on cardiovascular health. They conducted a study on randomized 36,282 postmenopausal women ages 50 to 79 years old at 40 clinical sites nationwide. Half of the participating women were given 500mg calcium carbonate supplements with vitamin D 200 IU (GlaxoSmithKline, Consumer Healthcare) twice daily, while the other half was given with placebo. After 7 years, cases of coronary heart disease (CHD) and stoke were evaluated. Results showed that in the group of women subjected to the active calcium/vitamin D supplement, 499 were reported to have myocardial infarction or CHD death and 362 suffered from stroke. On the other hand, in the group of women given with placebo, 475 cases of myocardial infarction or CHD deaths and 377 stroke cases were reported. Statistical analysis on this data shows a very low hazard ratio on the effect of calcium/vitamin D on cases of myocardial infarction or CHD (1.04 at 95% confidence interval) and on cases of stroke (0.95 at 95% confidence interval). Therefore, the team concluded that calcium/vitamin d supplementation neither increase nor decreased cardiovascular risks. This result is in contradiction with other previous studies that shows the positive effects of increased calcium intakes to cardiovascular health such as: the betterment of high-density lipoprotein to low-density lipoprotein ratio (HDH/LDL) in postmenopausal women [5]; and the increase on saturated fats contents in feces of men with calcium-fortified diets [6]. However, these studies were only short term and the HDH/LDL ratio and fecal saturated fat content are only indices of cardiovascular health and they do not fully portray the condition of cardiovascular health. In contrary, WHI CaD’s study is the first long-term study conducted to featuring the actual number of respondents inflicted with cardiovascular diseases. The limitation of this study is that, the women involved in the study were allowed to continue their own calcium supplements because “it would have been unethical to prohibit concurrent calcium use in a long-term, placebo controlled trial”. [4] Supposing a woman from the placebo group drinks calcium fortified milk twice to thrice a day, this may compensate to the difference in calcium in take between the placebo and the treatment group. In this case, the results may be skewed. Dr. Mark Bolland and colleagues from the University of Auckland, NZ seems to disagree with WHI CaD’s results. In their first study in 2008, the group conducted randomized, placebo controlled clinical trials in 1471 postmenopausal women. [7] Unlike the study of WHI CaD, Bolland’s group excluded women who are receiving treatment for osteoporosis; or those taking other calcium supplements; or those with major ongoing diseases such as hepatic, thyroid or renal dysfunction, malignancy or bone disease. The women received either 1g of elemental calcium supplement daily (citracal; Mission Pharmacal) or identical placebo. The results showed that myocardial infarction was more common in the treatment group (45 events in 31 women) compared to the placebo group (19 events in 14 women). Stroke and sudden death was also more common in the calcium group, 109 events in 69 women compared vs 54 events in 42 women in the placebo group. Therefore, Bolland’s results contested the previous studies that increased calcium intakes are beneficial to cardiovascular health [6], [5], or the report that calcium supplements does not have cardiovascular risks [4]. Their results show that calcium supplement increases the risk of cardiovascular problems. The weakness of their study is the small sample size. The volunteers were also comprised of the elderly and white race so the results cannot be generalized to all ages and racial groups. Bolland’s group recognize these limitations and conducted subsequent researches in 2010 [8] and 2011 [9]. This time instead of doing live clinical trials, they made use of available data from other studies. In the 2010 report, the group searched Medline, Embase and Cochrane Central Register of Controlled Trials for clinical trials and meta-analyses of calcium supplements by other groups. They were able to come up with 15 studies which are randomized, placebo-controlled, calcium supplements were ≥500 mg per day, with more than 100 participants aged 40 and above. The data, including all the health reports were provided by the lead authors of the studies they have selected. [8] In the 2011 report, they made use of the data generated by (WHI CaD), reported early on in this paper. [4] However, instead of merely analyzing the data of the treatment group vs the placebo group, like how the data was previously analyzed by WHI CaD, Bolland’s group took into account the effect of the personal calcium supplements consumed by the participants. They further divided the placebo group into two: those that have personal calcium intake and those without any calcium intake. [9] When the effect of personally administered calcium supplements by the respondents was taken into consideration, WHI CaD’s previous assumption was significantly reversed. Borland’s team showed that calcium supplement intake with [9] or without [8] coadministered vitamin D are associated with increased risks of myocardial infarction, stroke and stroke leading to death. As this is the first study to show wide-scale effect of calcium supplements in cardiovascular risks, the results presented by Borland’s group was criticized heavily by skeptics. Reviews on the study profoundly stated that the data used in the 2010 reports were mostly unpublished and were only taken by means of communication with other researchers. They also pointed out the inconsistencies in considering the basal dietary calcium intake. Reviews said that if the basal dietary calcium intake (approx 805mg/day) was also considered and added to the amount of supplemented calcium, this would also exceed the current allowable calcium intake per day of 1300mg. [10], [11], [12], [13] Although the results of Bolland’s group was showered with disapprovals, it is still factual that the reported increase in the risk of cardiovascular diseases in increased levels of calcium intake could be due to vascular calcification. [14] This occurs when calcium salts (e.g. Calcium phosphate) builds up in the form of bioapatite in the blood vessels, myocardium and cardiac valves. Calcified deposits are associated with vascular stiffening and highly correlated with cardiovascular disease mortality. [15] Therefore, elevated calcium level in the blood caused by intakes of calcium supplements could possibly induce vascular calcification. In conclusion, recent suggestions of the potential harm of calcium supplements have generated debates within the scientific community. This only means that more unbiased studies should be presented and more researches should be done in order to prove the link between increased calcium intake and cardiovascular diseases. Works Cited 1. Mackay, J., et al., The atlas of heart disease and stroke. 2004, Geneva: World Health Organization. 18-24. 2. Thygesen, K., et al., Universal definition of myocardial infarction. European Heart Journal, 2007. 28(20): p. 2525-2538. 3. Medicine, C.t.R.D.R.I.f.V.D.C.I.o., Dietary Reference Intakes for Calcium and Vitamin D, ed. A.C. Ross, et al. 2010: The National Academies Press. 4. Hsia, J.H., et al., Calcium/Vitamin D Supplementation and Cardiovascular Events Circulation, 2007. 115: p. 846-854. 5. Reid, I.R., et al., Effects of calcium supplementation on serum lipid concentrations in normal older women:: A randomized controlled trial. The American Journal of Medicine, 2002. 112(5): p. 343-347. 6. Denke, M.A., M.M. Fox, and M.C. Schulte, Short-Term Dietary Calcium Fortification Increases Fecal Saturated Fat Content and Reduces Serum Lipids in Men. The Journal of Nutrition, 1993. 123(6): p. 1047-1053. 7. Bolland, M.J., et al., Vascular events in healthy older women receiving calcium supplementation: randomised controlled trial. BMJ, 2008. 336(7638): p. 262-266. 8. Bolland, M.J., et al., Effect of calcium supplements on risk of myocardial infarction and cardiovascular events: meta-analysis. BMJ, 2010. 341. 9. Bolland, M.J., et al., Calcium supplements with or without vitamin D and risk of cardiovascular events: reanalysis of the Womens Health Initiative limited access dataset and meta-analysis. BMJ, 2011. 342. 10. Nordin, B.E.C., et al., Making too much of a weak case. BMJ, 2010. 341. 11. Richard, L.P., Z. Kun, and R.L. Joshua, Evidence of harm is unconvincing. BMJ, 2011. 342. 12. Joan, M.L. and P.H. Robert, Results may not be generalisable. BMJ, 2008. 336. 13. Bess, D.-H., The heart of the matter. BMJ, 2010. 341. 14. Goldsmith, D., E. Ritz, and A. Covic, Vascular calcification: A stiff challenge for the nephrologist. Kidney International, 2004. 66: p. 1315-1333. 15. Giachelli, C.M., Vascular Calcification Mechanisms. Journal of the American Society of Nephrology, 2004. 15(12): p. 2959-2964.  Read More