Habrdness of water has a beneficial effect againts which one of the following -

Repos from several countries have shown an inverse statistical association between the hardness of drinking water and the death rate from cardiovascular diseases. Areas supplied with soft drinking water showed a significantly higher prevalence of either aeriosclerotic disease or degenerative hea disease, hypeension, the sudden death of cardiovascular origin. Park's Textbook of Preventive and Social Medicine, 25th edition, Page No. 787