Hard-water theory

Plain as it looks, that glass of water may protect you against coronary artery disease and heart attacks.

Seeking to explain why heart attack rates vary by geography in Finland, researchers there decided to look at the environment -- at groundwater, specifically. They divided Finland into a geographical grid and studied regional variations in water hardness (the amounts of dissolved calcium and magnesium), and in the calcium, magnesium, fluoride, iron, copper, zinc, aluminum and nitrate in more than 12,000 groundwater samples.

By combining the geographic data with hospital or death records of nearly 19,000 men ages 35 to 74 who had had a first heart attack, the researchers were able to establish a correlation.

Generally, water hardness was lower in the east, where there was more heart disease, and higher in the west and south, where there was less heart disease. For every unit increase in the hardness of local water, the risk of having a heart attack fell by 1%.

The researchers couldn’t find direct associations between groundwater mineral content and heart attack rates, although they found suggestions that fluoride provided some protection and that copper and iron could boost risk.

Writing in the February issue of the Journal of Epidemiology and Community Health, the authors, led by Dr. Anne Kousa of the Geological Survey of Finland, said additional studies should focus on nutrients in water and food.