Does calcium lower your chances of stroke?

This study looked at whether dietary calcium intake decreases stroke risk.

A stroke occurs when there is a disturbance of blood supply to a part of the brain. This can be caused by a blood clot in the brain (ischemic stroke) or a burst blood vessel (hemorrhagic stroke). Both types of stroke result in a lack of oxygen and food reaching the brain tissue and can cause brain damage.

Recent evidence suggests that calcium may lower the risk of cardiovascular disease. Cardiovascular disease generally refers to narrowed or blocked blood vessels that can lead to stroke. Calcium is thought to lower the risk of cardiovascular disease and stroke by having various beneficial effects on stroke risk factors such as blood cholesterol concentration, blood pressure, insulin release and response (important for diabetes), inflammation, blood clots, and obesity.

This study carried out a review of 11 previous studies with a total 9,095 cases of stroke that all investigated the effects of calcium on stroke risk. Patients that increased their calcium intake to 300 mg per day were found to have an 18% reduction in stroke risk. This beneficial effect of calcium on stroke risk was seen similarly among all patients that consumed a low to moderate average intake of dietary calcium (<700 mg per day). However, high calcium intake (>700 mg/day which is more than the daily recommendation for adults) had no effect..

These different effects of calcium at different doses appear to be dependent on race, however, as all calcium doses decreased the risk of stroke in Asian populations. 

This study concludes that dietary calcium intake may decrease the risk of stroke in populations with low to moderate calcium intakes and in Asian populations. 

The study did not take into account the rest of the participants' diet; hence, it is likely that those consuming a high calcium diet also consume a lot of other foods that could be negatively effecting stroke risk and may explain the lack of evidence that high calcium intake reduces stroke risk. Also, it is thought that the source of calcium affects the stroke-risk reducing ability; for example, calcium from a diary source, in particular low-fat dairy, may be absorbed better and responsible for reducing the risk of stroke. 

If you or someone you know want to reduce the risk of stroke, talk to a doctor or dietician about ways you can consume between 300-700 mg per day of calcium from low-fat dairy sources.