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Calcium dementia link is reminder of the dangers of supplements
An increased risk of dementia in some women taking calcium warns us that supplements marketed as a quick fix for health may not be benign, says Clare Wilson
Taking supplements to be ‘on the safe side’ doesn’t necessary produce the desired benefits
By Clare Wilson
Taking a daily vitamin or mineral supplement is widely seen as a common-sense way of looking after yourself – a kind of insurance, like wearing a seat belt.
But evidence is growing that it might not be such a healthy habit after all. The latest finding is that calcium supplements, taken by many women after the menopause to strengthen their bones, are linked to dementia. Among women who have had a stroke, taking calcium was associated with a seven-fold rise in the number who went on to have dementia. Calcium was also linked with a smaller, non-statistically significant, rise in dementia in women who had not had a stroke.
The finding emerged from a study that was not a randomised trial, so it is not the most robust type of medical evidence. The researchers merely counted dementia cases in people who had chosen whether to take calcium, and so the data could be biased. But the results are striking and come on the heels of a previous study that was a randomised trial, which found a link between calcium supplements and a modestly higher risk of heart attacks – suggesting that caution over calcium is indeed warranted.
If future research confirms the association with dementia, women would face a horrible dilemma: should they continue to take calcium, staving off bone weakness that can lead to fatal hip fractures, while running an increased risk of one of the most dreaded illness of ageing?
No magic wand
So what’s going on? Team member Silke Kern at the Sahlgrenska Academy Institute of Neuroscience and Physiology in Gothenburg, Sweden, says that taking a calcium pill triggers a rapid surge in the mineral’s levels in the blood, one that you wouldn’t get from calcium in food. Such a spike could make blood more likely to form harmful clots – which could trigger heart attacks – or could harm brain cells, resulting in a higher incidence of dementia, she says.
But there are wider lessons here. The importance of vitamins and minerals in our diet emerged mainly in the early 20th century thanks to striking deficiency diseases seen in the poor. For example, children grew up with the bowed legs of rickets, caused by a lack of vitamin D.
The discovery that we could make such nutrients artificially and add them to food or turn them into pills must have seemed like a magic wand for health. It was understandably tempting to conclude that even well-fed individuals might benefit from taking supplements, “to be on the safe side”.
Today about a two-thirds of people in the US take a daily supplement. This includes those who take multivitamin and mineral pills, as well as people who take individual ones, like calcium, or combinations targeted at certain health needs, like protecting ageing joints, preventing colds or promoting hair and nail health.
But while adverts for such pills can be slick, often featuring athletes and celebrities testifying to their benefits, the evidence is remarkably lacking. In the US and UK, there is, shamefully, no need for supplement-makers to carry out trials showing their products have the claimed effects.
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Rather than just failing to do good, some supplements may even be harmful – as with calcium.
People also like to take antioxidants – including the vitamins A, C and E, and the mineral selenium – because of the belief they ward off cancer by blocking damaging oxidising compounds produced during metabolism.
But when put to the test, this idea falls down spectacularly. Trials show that those taking antioxidants have a slightly higher death rate than those who don’t.
The explanation for this finding is still unclear. It could be because we have misunderstood how antioxidants work, or because plants contain thousands of protective phytochemicals and taking a few in isolation just doesn’t have the same benefits.
In the case of calcium, it isn’t too hard to get all we need from natural sources. The UK recommended intake of 700 milligrams a day could be met by consuming, for instance, 300 millilitres of milk, a 100-gram pot of yogurt and a small 30-gram wedge of cheese. (The US recommended daily amount is a bit higher, at 1000 milligrams for most adults and 1200 milligrams for over-70s, but not unfeasibly so.)
With the exception of folic acid, which trials have shown prevents birth defects if taken before and during pregnancy, many dieticians now say that supplements are no substitute for a healthy and varied diet, with plenty of fruit, vegetables and dairy produce or its equivalents. There’s no better health insurance than that.
Journal reference: Neurology, DOI: 10.1212/WNL.0000000000003111