To reduce the risk of osteoporosis, the NIH recommends that elderly people consume 1,000 to 1,200 mg of calcium per day. Since this is difficult to obtain from food alone (for reference, a glass of milk contains less than 300 mg), many people take calcium supplements to reach their daily minimum. However, this recommended daily intake has recently received some criticism from the scientific community, with several studies failing to find a relationship between calcium intake and bone density.
In fact, it’s possible that high calcium intake could be harmful to our health. A 2008 review found that hyperparathyroidism, a condition that causes abnormally high levels of calcium in the blood, can contribute to cardiovascular disease. Since hypertension, diabetes, and other cardiovascular problems increase the risk of both vascular dementia and Alzheimer’s disease, the results of this study raised the question of whether calcium supplements could play a role in dementia.
In a recent study published in the journal Neurology, researchers observed 700 Swedish women between the ages of 70 and 92, all of whom were initially dementia-free. At the beginning of the study, women who took calcium supplements did not differ significantly in age, scores on cognitive exams, or education level. After a five-year follow-up, the women taking calcium supplements were twice as likely to be diagnosed with any dementia and more than four times as likely to be diagnosed with vascular dementia. There was no association observed between calcium supplements and Alzheimer’s disease.
Future analysis of the data revealed that the increase in dementia risk among calcium supplement users only existed in women who had a history of stroke or who had white matter lesions (small regions of damaged brain tissue that can result from cardiovascular disease). Women without these conditions had the same dementia risk regardless of calcium consumption. Notably, women who took calcium supplements had only a 20% risk of experiencing a bone fracture during the course of the study, while those who did not take the supplements had a 40% risk of fractures.
The authors of this study offered several possible explanations for these results. One possibility is that high levels of calcium in the blood could increase the risk of neurons dying near the site of a stroke, as other studies have shown that calcium is involved with apoptosis and necrosis (two forms of cell death). Calcium could also be affecting the blood or vasculature directly. The authors also pointed out that dietary calcium does not lead to the same spikes in blood calcium levels as calcium supplements, so consuming calcium in our food instead of pills may avoid these possible cardiovascular risks.
This study has several important limitations. The analysis looked only at whether or not the women took calcium supplements and did not consider the amount of calcium consumed in food. The sample size was also fairly small, with only 98 dementia diagnoses in the cohort, of whom 14 took calcium supplements. Since only women were included, these results may not generalize to men. Finally, being an observational study, the results cannot establish a causal relationship between calcium and dementia (see How to Be a Smart Consumer of Science News), so further research utilizing randomized assignment is needed to determine whether calcium or a different factor caused the observed discrepancy in dementia incidence.