DIETARY CALCIUM, VITAMIN-D, AND THE RISK OF COLORECTAL-CANCER IN STOCKHOLM, SWEDEN

The epidemiology of large bowel cancer suggests an etiological role fo r dietary factors. Although the evidence is inconsistent, several stud ies have suggested an inverse association between dietary vitamin D or calcium and colorectal cancer risk. We conducted a population-based c ase-control study to examine the relationship between dietary vitamin D and calcium and colorectal cancer among residents of Stockholm, Swed en. Between January 1986 and March 1988, 352 cases of colon cancer and 217 cases of rectal cancer diagnosed among living persons residing in Stockholm County were identified via a cancer surveillance network es tablished among all the hospitals in Sweden and the Stockholm Regional Cancer Registry. Controls (512) were randomly selected from a compute rized population registry, Dietary intake was assessed using a quantit ative food frequency questionnaire focusing on average consumption dur ing the preceding 5 years. Supplemental intake of vitamin D and calciu m was not ascertained, Logistic regression was used to calculate odds ratios (ORs) as the measure of association between the exposure of int erest (vitamin D or calcium) and cancer risk. Increasing levels of die tary vitamin D were inversely associated with the risk of colorectal c ancer. The association was somewhat more pronounced for cancers of the rectum [OR, 0.5; 95% confidence interval (CI), 0.3-0.9 between the hi ghest and lowest quartiles] than for cancers of the colon (OR, 0.6; 95 % CI, 0.4-1.0) after adjustment for age, sex, and total caloric and pr otein intake. Dietary calcium was not associated with the adjusted ris k of colon (OR, 1.2; 95% CI, 0.7-2.1) or rectal cancer (OR, 1.0; 95% C I, 0.5-1.9). Further adjustments for fat and dietary fiber intake, bod y mass index, and physical activity had little or no effect on the res ults. These results suggest that dietary vitamin D may reduce the risk of large bowel cancer, particularly rectal cancer. In addition, altho ugh some of the previous data suggested a protective effect for calciu m against cancers of the large bowel, we could not document such an ef fect.