CALCIUM, MAGNESIUM, AND NITRATE IN DRINKING-WATER AND GASTRIC-CANCER MORTALITY

The possible association between the risk of gastric cancer and the le vels of calcium, magnesium, and nitrate in drinking water from municip al supplies was investigated in a matched case-control study in Taiwan , Records of gastric cancer deaths among eligible residents in Taiwan from 1987 through 1991 were obtained from the Bureau of Vital Statisti cs of the Taiwan Provincial Department of Health, Controls were deaths from other causes and were pair-matched to the cases by sex, year-of- birth, and year-of-death. Each matched control was selected randomly f rom the set of possible controls for each case. Data on calcium, magne sium, and nitrate levels in drinking water throughout Taiwan were obta ined from the Taiwan Water Supply Corporation. The municipality of res idence of the cases and controls was assumed to be the source of the s ubject's calcium, magnesium, and nitrate exposure via drinking water, The subjects were divided into tertiles according to the levels of cal cium, magnesium, and nitrate in their drinking water The results of th e present study show that there is a significant positive association between drinking water nitrate exposure and gastric cancer mortality. The present study also suggests that there was a significant protectiv e effect of calcium intake from drinking water on the risk of gastric cancer, Magnesium also exerts a protective effect against gastric cant er, but only for the group with the highest levels.