The study followed 41,526 Japanese men and women aged between 40 and 59, and the results are published in the American Heart Association’s journal Stroke.
Diet is known to have an impact on a person's risk of having a stroke, and in particular a connection has been made between intake of sodium and hypertension. Conversely, more magnesium, potassium and calcium has been inversely linked to hypertension in some observational studies.
Despite these links, the researchers state that no prospective studies have examined the link between calcium intake and the incidence of stroke in Japanese men and women with a low average calcium intake.
The results from the Japanese population are at odds with a recent study based in Europe. Researchers from the Karolinska Institutet in Sweden set out to examine the association between these minerals and the risk of stroke in male smokers.
In the study, published in the Archives of Internal Medicine, they found that, magnesium intake in the diet appeared to significantly reduce the risk of stroke.
However, calcium, potassium and sodium were not associated with risk of any type of stroke.
Researchers from the University of Tsukuba, Osaka University, and Japan’s National Cancer Center, and National Cardiovascular Center, used food frequency questionnaires (FFQ) to assess dietary intakes of the 41,526 men and women in the study.
Over the course of the study, which lasted from 1990 to 2003, the researchers documented 1,321 strokes, and 322 cases of coronary heart disease.
Lead author Mitsumasa Umesawa reports that total calcium intake from all sources was associated with a 30 per cent reduction in the risk of having a stroke.
Moreover, when the researchers considered only calcium from dairy sources, they found that the risk of stroke was also reduced by 30 per cent, but there was no associated with coronary heart disease.
“Dietary calcium intake, especially calcium from dairy products, was found to be associated with a reduced incidence of stroke among middle-aged Japanese,” concluded the researchers.
Source: Stroke Published online ahead of print 17 July 2008, doi: 10.1161/STROKEAHA.107.512236“Dietary Calcium Intake and Risks of Stroke, Its Subtypes, and Coronary Heart Disease in Japanese. The JPHC Study Cohort I”Authors: M. Umesawa, H. Iso, J. Ishihara, I. Saito, Y. Kokubo, M. Inoue, and S. Tsugane, for the JPHC Study Group