Effect of a Western-style diet fortified with increased calcium and vitamin D on mammary gland of C57BL/6 mice.

ABSTRACT We previously reported hyperproliferation and hyperplasia in C57Bl/6 mouse mammary gland after feeding a Western-style diet (WD); these findings decreased after supplementing WD with increased calcium and vitamin D3. We now again fortified WD with increased calcium and vitamin D3 from two sources: (1) a food source, calcium- and vitamin D3-enriched yogurt (WDy diet) or (2) adding calcium and vitamin D3 directly to WD (WDCaD diet). After 6 months of feeding the number of mammary ducts was higher in mice consuming WD compared to WDy (216.0 vs. 202.7, P <.05) and WDCaD (216.0 vs. 194.9, P <.001). The percentage of small ducts increased in WD compared to AIN-76A controls (23.3% vs. 17.4%) but was lower in the WDy (17.1%) and WDCaD (14.8%) groups. WD mice had higher numbers of epithelial cells per duct than WDy (33.2 vs. 27.4, P <.001) and WDCaD (33.2 vs. 27.8, P <.001) mice, and AIN-76A-fed mice had higher numbers than WDy (31.1 vs. 27.4, P <.005) or WDCaD (31.1 vs. 27.8, P <.01) mice. Mitotic index ...