For decades, women have been told to take calcium supplements to build strong bones. Many health professionals dismiss the value of multivitamins but have been enthusiastic about supplemental calcium. The idea has been that this would help build bone and prevent fractures, even though there is no evidence that this is effective. (You can read more about that here.)
The Dangers of Too Much Calcium:
Most people think of calcium supplements as safe. In fact, there are lots of foods and beverages that are fortified with extra calcium. Some experts worry, however, that supplemental calcium may not be as innocuous as it seems.
Several studies have suggested that calcium supplements might increase a person’s chance of suffering a heart attack or stroke. An enormous observational study of 400,000 adults, the NIH-AARP Diet and Health Study, found that high-dose calcium supplements were associated with an increased risk for cardiovascular complications in men (JAMA Internal Medicine, April 22, 2013). We wrote about that and other research suggesting risks of calcium supplementation here.
Although the NIH-AARP study did not find an increased risk in women, a Swedish study of more than 61,000 women followed up for 19 years found that those taking 1,400 mg or more of calcium daily were more likely to die from any cause or from heart attacks, though not from stroke (BMJ, online Feb. 13, 2013). You can read more about that research here.
Do Calcium Supplements Increase the Risk for Dementia?
A recent study of 700 Swedish women between the ages of 70 and 92 suggests that some of those taking calcium supplements to protect their bones may be inadvertently harming their brains.
More than half of the women who agreed to participate in the research had CT scans done of their brains at the beginning of the five-year study. Nearly three-fourths of these scans, 71 percent, showed lesions in the white matter of the brain. Such lesions indicate cerebrovascular disease. Just a few of the participants, 98, were taking calcium supplements at the time. 54 women had a history of stroke. All of the women took tests to assess their memory and cognitive function at the outset.
After five years of follow-up, some of the women had developed dementia. Specifically, 59 of the volunteers had scores on their cognitive function tests that had dropped dramatically into the range of dementia. Women who had had strokes were almost seven times more likely to be diagnosed with dementia if they took calcium supplements. Those with with white-matter lesions were three times more likely to land in the dementia category if they were taking calcium.
The authors conclude, “Calcium supplementation may increase the risk of developing dementia in elderly women with cerebrovascular disease.” They point out that these findings are preliminary and deserve further investigation. We agree that the numbers of women with strokes or dementia in this study are too small to support strong conclusions.
We would encourage people to take calcium supplements if the benefits were clear and there were no risks. Sadly, neither seems to be true at this point in time. The benefits have been controversial for years, especially with regard to osteoporosis prevention. Evidence has been accumulating that there may be significant risks.
We urge women who have had strokes or TIAs to discuss calcium use with their doctors. We cannot judge whether calcium poses a risk of dementia for otherwise healthy women. People who would like to get their calcium from food rather than supplements may wish to consult the list in this article. You may also be interested in our Show #752 on Bone Vitality. It is an hour-long interview with Michael Castleman and Walter Willett, MD, DPH, Chair of the Department of Nutrition at the T. H. Chan School of Public Health at Harvard University.