I watched the CNN program about “the dangerous new development” reported in the July 29th issue of the British Medical Journal that people who take calcium regularly increase their risk of heart attacks.
I have significant osteopenia and family risk factors for heart disease although my cholesterol, weight, blood pressure and lifestyle are really quite healthy.
What is the right thing to do?
Science and medicine are often not black and white in their observations and discoveries. This is new information, and it was somewhat distorted–as is to be expected–by the news media. As you noted, the CNN journalist called the information from this evaluation of many studies–which included both calcium intake and rate of cardiovascular disease–a “dangerous new development.” But these studies were not designed to evaluate whether or not cardiovascular events would increase if 10,000 people took calcium without vitamin D and 10,000 people took no calcium at all for many years.
This new information is important, though, and not just because a question has been raised about the safety of calcium use. We know now that vitamin D is essential in the prevention and treatment of bone loss. There is evidence that vitamin D may be important in lowering cardiovascular disease. This encourages doctors and patients to make sure that they have daily supplements of vitamin D, certainly higher than the currently recommended dose.
This study is even more important because it raises the larger issue of just what patients are taking when they go to the health food store or visit online sites and order fish oil supplements, along with dozens of herbal preparations for “immune enhancement” and for other vague preventive issues.
I am checking patients who take fish oil supplements for mercury levels and have found extremely high levels of mercury in several patients. This is an anecdote, not a study, but it does point out that everything we put in our mouths or rub on our skins is a drug, whether it is “organic,” “natural,” or recommended by your masseuse. Take only what is necessary, eat a balanced diet, exercise as much as you can, and do not stop your calcium based on this one report. Do ask your doctor to check your vitamin D levels and ask if you may safely take 2000IU of vitamin D every day.
I have asked three members of our Medical Advisory Board to weigh in on this important question. Dr. Susan Thys-Jacobs and Dr. Naina Sinha are both respected endocrinologists who care for patients and are involved in research in the area of osteoporosis. Dr. Timothy Dutta is a cardiologist with an interest in preventive care, among other aspects of his practice. I did not expect that all three of these physicians would respond to this new information in the same way, and they did not. We know now that this is a new area of study, and that it is certainly too early to make black and white decisions based solely on this news.
Susan Thys-Jacobs, M.D.
Calcium is the most important mineral in the body and many people fail to consume adequate dairy on a daily basis. Because an extensive body of evidence has linked calcium and vitamin D to overall wellbeing, optimal bone health, reduction in cancer risk, as well as beneficial effects on hypertension, more Americans are supplementing their calcium intake.
The article by Mark Bolland and colleagues published in the British Medical Journal and subsequently cited by CBS News and CNN.com is misleading and unfortunate, as it now questions the benefit of calcium supplement use. The authors found that calcium supplementation at doses greater than 500 mg daily were associated with an increased risk of cardiovascular events and heart attacks.
The authors of the BMJ article sought to investigate whether the use of calcium supplements increased the risk of cardiovascular events by means of a meta-analysis study. In other words, their study was a pooled analysis of prior investigations, in which the primary intent of the original study was not the underlying purpose of this meta-analysis.
The pooled studies were not specifically designed to test the effect of cardiovascular risk. None of the trials selected had cardiovascular outcomes as the primary end points, and data on cardiovascular events were not gathered in a standardized fashion. Although 15 studies were pooled for data, only 5 studies had complete patient data available for cardiovascular outcome assessment. The remainder had either partial data or no cardiac data. Furthermore, two of the studies included did not have the typical placebo group, as subjects were either taking vitamin D or Alendronate.
Yet these authors concluded that a reassessment of the role of calcium supplements in the management of osteoporosis is warranted. They also concluded that their data was consistent with trials of patients with renal failure, in which calcium supplementation was associated with an increased overall mortality. However, renal failure patients have a tendency to retain phosphorus, as they are unable to excrete phosphorus adequately, thereby increasing their calcium-phosphate ratio resulting in an increased risk of vascular calcification. The pathophysiology of the renal failure patient is very different from those with normal renal function.
Many previous calcium studies have not found significant differences in cardiovascular or stroke risk between those using calcium supplements and those who are not. These studies include:
- Bakta M. et al., Journal American Board of Family Medicine 2009. Found that oral calcium supplements do not affect the progression of aortic valve calcification or coronary artery calcification.
- Al-Delaimy et al., American Journal of Nutrition 2003. Prospective study of calcium intake from diet and supplements and risk of ischemic heart disease among men. Very large study of 39, 800 participants demonstrated no effect on cardiovascular risk.
- A systematic review of the effect of vitamin D and calcium on cardiovascular risk conducted by another group (Wang and colleagues) at the Harvard School of Public Health, published in March in the Annals of Internal Medicine, found that calcium supplements have minimal cardiovascular effects.
Bolland and colleagues’ investigation should be interpreted with some healthy skepticism, before anyone decides to discontinue their calcium supplements. Prospective calcium trials are indeed warranted.
Timothy Dutta, M.D.
Once again, doctors and patients are surprised to hear that one of the easiest and most common supplements we use may be dangerous. Calcium supplements have always been easy for patients to take and doctors to recommend. The hypothesis is simple: women who have low calcium intake get osteoporosis; thus, increasing calcium intake should prevent osteoporosis.
Osteoporosis is a major health risk for the elderly; hip or spine fractures can be life ending, both literally and figuratively. Even though large trials have shown only a small benefit from calcium, doctors and patients have long felt there is no harm in taking it. More potent osteoporosis treatments have known risks and side effects, so there has always been a sense of safety when recommending calcium.
It now appears that calcium may have significant risks.
New analysis of old data shows there may be an important risk of heart attack with calcium supplements. A collection of eleven trials shows there is potentially a 30% increase in the risk of heart attack for those taking calcium supplements. It’s hard to argue that there is some truth to this when each of the eleven individual studies showed this trend.
The mechanism for this can be speculated upon, and the degree of risk can be debated. But no matter what, this leads to reconsideration of who should take calcium. Millions of people take these supplements, so even a small increase in risk affects a large number of people.
Many patients should discontinue the supplements, but the decision needs to be individualized between patients and their doctors. Risk factors for heart attack need to be weighed against risk factors for osteoporosis.
Is this another case of the medical establishment flip flopping with our recommendations? Is this another moment of confusion when long established guidelines are challenged? Yes, but it is also medical progress. State-of-the-art treatments of yesterday are now obsolete, and our best treatments of today will be surpassed by better treatments tomorrow. This new information allows doctors to make better recommendations and patients to make better decisions.
Naina Sinha, M.D.
Do calcium supplements increase the risk for heart attacks?
A July 2010 study published in the British Medical Journal found that calcium supplements are associated with an increased risk for heart attacks. Before we start throwing away all our calcium tablets it is important that we understand what this study actually found.
First, this study looked at calcium supplements that did not contain vitamin D. Vitamin D deficiency has been associated with increased risk of heart disease and there have been studies showing that vitamin D supplementation is associated with decreased mortality.
Second, the study was a meta-analysis, which means that many smaller studies were grouped together and all the results combined to form one set of conclusions. This type of study is not the gold standard for medical research and the results must be interpreted with caution.
An important point to realize it that this study looked at calcium supplementation, not dietary calcium. In previous studies, women with high levels of dietary calcium intake have been found to have a decreased risk of stroke and heart disease.
We know that calcium and vitamin D are important for bone health and can prevent fractures. So what should women do to take care of their bones but not increase their risk for heart disease? Until more rigorous studies are done do determine what it is about calcium supplementation that is leading to increased heart disease, the best thing to do is get your calcium through food sources including dairy sources like milk, cheese and yogurt or non-dairy sources like almonds, kale, tofu, and spinach. Also, remember to take supplemental vitamin D and have your vitamin D level checked by your doctor to make sure you are getting enough but not too much.