Diet and gallstones in Italy: the cross-sectional MICOL results

Fifteen thousand nine hundred ten men and 13,674 women (age, 30-69 years) were enrolled in an epidemiological survey of the general population, between December 1984 and April 1987. Each participant was submitted to ultrasonography (US) of the gallbladder and completed a food-frequency questionnaire, covering 38 food items. A common portion size was identified and subjects were asked how often each item was consumed. Nutrient intake was computed by multiplying the intake frequency and nutrient content per portion for each item, and then by summing the product over all foods. Each nutrient intake was adjusted for energy intake. Alcohol intake was calculated by summing the consumption of wine, beer, and liquor. Having excluded subjects aware of having gallstones (GS) or previously submitted to cholecystectomy (to avoid prothopatic bias), 787 males and 1,014 females with GS and 14,272 males and 10,836 females without GS were available for analysis. Relative risks (RR) of GS were computed by quintiles of nutrient intake. The overnight fasting period was calculated as the difference between the specified time of dinner and the time of the next meal (breakfast or lunch). A significant negative association was found between RR of GS and total energy intake for males (chi2 for trend = 8.37; P = .004), fiber intake for females (chi2 = 5.45; P = .02), and daily alcohol consumption for males (chi2 = 10.86; P = .001). A positive association was observed between RR of GS and carbohydrate (chi2 = 5.95; P = .01 for males; chi2 = 9.39; P = .002 for females) and protein intake only for males (chi2 = 10.92; P = .01). Prevalence of GS was higher among subjects who had an overnight fasting period of over 12 hours than subjects with that of less than 12 hours. (RR: 1.35; 95% CI: 1.01-1.80 for males; RR: 1.28; 95% CI: 1.03-1.60 for females). These data do not confirm that high energy intake is associated with an increased risk of GS. Factors protecting against GS comprise: low carbohydrate (males and females) and protein (males) intakes, high fiber (females) and moderate alcohol intake (males) consumption, and a shorter overnight fasting period for both sexes.