RESUMO
BACKGROUND: Protection from thyroid carcinoma due to certain dietary factors was suggested by several studies, but the findings were relatively inconsistent. The role of micronutrients has not yet been systematically analyzed. To investigate the relationship between micronutrient intake and thyroid carcinoma risk, the authors used data from a case-control study conducted in northern Italy between 1986 and 1992. METHODS: The study included 399 incident, histologically confirmed thyroid carcinoma cases and 617 controls admitted to the hospital for acute, nonneoplastic, nonhormone-related diseases. RESULTS: Retinol intake showed a direct association with thyroid carcinoma risk, with odds ratios (ORs) of 1.39 (95% confidence Interval [CI], 0.9-2.0) in the third quartile of consumption and 1.52 (95% CI, 1.0-2.3) in the highest quartile, whereas beta-carotene had an inverse relationship, with ORs of 0.63 (95% CI, 0.4-0.9) in the third quartile of consumption and 0.58 (95% CI, 0.4-0.9) in the highest quartile compared with the lowest quartile. Some protection was observed for measures of vitamin C intake (with an OR of 0.72) and vitamin E (with an OR of 0.67) for the highest quartile of consumption, although the estimates were not statistically significant, and were reduced after adjustment for beta-carotene intake. No clear pattern in risk appeared for vitamin D, lolate, calcium, thiamin, or riboflavin. The inverse relationship between beta-carotene and thyroid carcinoma was observed in both papillary and follicular carcinomas. CONCLUSIONS: In this study, a significant inverse association between beta-carotene and thyroid carcinoma was observed, and some protection against thyroid carcinoma from vitamins C and E was also suggested.