The relationship of dietary intake and serum levels of retinol and beta‐carotene with breast cancer. Results of a case‐control study

The possible association between the risk of breast cancer, blood level, and dietary intake of preformed Vitamin A (retinol) and beta‐carotene was investigated in a case‐control study carried out from May 1982 to June 1985. The patients studied were 214 previously untreated individuals with T1‐2, N0‐1, M0 breast cancer admitted to the National Cancer Institute of Milan and 215 controls admitted for conditions other than neoplastic or metabolic disorders. Both cases and controls were selected from an age group ranging from 30 to 65 years old. Plasma levels of retinol and beta‐carotene were tested from blood samples drawn during the first day after admission to the hospital. A questionnaire about diet was used to estimate the mean intake of 69 food items from which a daily dietary index of retinol and beta‐carotene intake was computed. Information relating to the woman's history, socioeconomic status, and known risk factors for breast cancer was also collected. No association was found between beta‐carotene (in the diet or blood) or dietary retinol and the risk of breast cancer. As for blood retinol, our data show a significant trend of increasing risk with higher levels; multivariate relative risk for subsequent serum levels based on the control quintiles, are 1, 1.5, 1.8, 1.7; (test for linear trend: chi‐square = 8.26). Thus, these findings, together with the results of other studies,47,48 suggest that retinol and beta‐carotene are unlikely to be related to the risk of breast cancer.