The suggestion that taking calcium supplements might increase the risk of dementia comes from data involving 700 women, aged 70 and over, living in Sweden.
The women, who were initially free from dementia, had an initial neuropsychiatric examination and were then re-assessed five years later. Of these, only 98 (14%) were taking calcium supplements at the start of the study but, after 5 years, this number had dropped to 50 so the number of women on which the findings were based was small.
Even so, the women taking calcium supplements appeared to have twice the risk of developing vascular dementia, and over four times the risk of stroke-related dementia, than the women not taking calcium supplements. Sounds scary, but things are not as clear-cut as they seem.
Although volunteers had blood tests to measure their cholesterol balance and to check for the APOE gene (known to increase dementia risk) they did not have their vitamin D levels checked. And, even though use of calcium supplements was documented, and participants were asked to show their medication to the researchers, no-one thought to record the doses! The researchers did state that the average recommended daily dose of calcium supplements in Sweden is 1000mg.
Why I’m not too concerned
A number of factors make these findings less worrisome than newspaper headlines had us believe.
Firstly, there was no association between taking calcium supplements and the development of dementia in women who did not have a previous history of stroke.
The association was only seen in women who had already experienced a stroke or who had CT evidence of white matter lesions, for whom taking calcium supplements appeared to increase the risk between six and seven-fold.
The frequency of bone fractures in women taking calcium supplements was also twice that of women not taking calcium supplements (40.8% versis 20.8%) suggesting that they had pre-existing factors associated with osteoporosis, such as vitamin D deficiency.
Of the 98 women taking calcium supplements initially, most also took vitamin D, although 14% did not. The authors confirmed via email that blood vitamin D levels were not measured to assess vitamin D status, however. This is important as, even in older people who take vitamin D supplements, it is often difficult to maintain adequate vitamin D levels.
Previous studies have shown that as many as one in two people in Sweden are deficient in vitamin D during the winter months. I would suggest that Swedish women with a previous history of stroke (and those who develop dementia) are even more likely to be vitamin D deficient as a result of being house-bound.
What’s more, these women who had experienced a stroke were probably also taking a statin, and statin drugs reduce the ability to synthesis vitamin D even further.
Prescribed vitamin D doses are often too low
People who are prescribed vitamin D alongside their calcium supplements to treat osteoporosis are usually given a standard dose that is not individually assessed by measuring vitamin D status.
It becomes increasingly difficult to maintain circulating vitamin D levels as you get older, and studies in the United States have shown that an intake of 100 mcg (4000 IU) is needed to maintain vitamin D levels in all older women (equivalent to the currently suggested EU Upper Safe Level). Despite this, the dose usually prescribed to prevent fractures in the ‘high risk elderly’ is just 800 units of vitamin D together with 1,200 milligrams of calcium.
If the correct dose is not individually determined via blood tests, it is difficult to maintain vitamin D status in older people. As a result, over 50% of women treated for bone loss continue to have inadequate vitamin D levels.
When vitamin D levels are low, more calcium remains in the circulation. Without vitamin D to direct its deposition in bone, calcium may promote hardening and furring up of the arteries and increase the risk of vascular (but not Alzheimer’s) dementia. It is not the calcium supplements per se that are the villain. The main problem is inadequate vitamin D support. Even so, in this Swedish study, the researchers found no association between taking calcium supplements and the development of dementia in women who did not have a previous history of stroke.
What about vitamin K?
Good intakes of vitamin K are also important when taking calcium supplements – especially the form known as vitamin K2. This is needed to regulate calcium deposition in the body, and to prevent calcification of arteries and other soft tissues.
What’s the take home message?
If you have previously had a stroke and your doctor prescribes calcium and vitamin D supplements to treat osteoporosis, ask to have your vitamin D levels checked regularly. Otherwise, you may be among those for whom the usually prescribed dose is too low. It’s also important to take a vitamin K2 supplement.
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