The antiproliferative effects of extracts of kefir, yogurt, and pasteurized cow's milk on (1) human breast cancer cells (MCF-7); and (2) normal human mammary epithelial cells (HMECs) was investigated at various doses. After six days of culture, extracts of kefir-fermented milk was found to inhibit MCF-7 cell growth in a dose-dependent manner, with 29% inhibition of proliferation at a concentration as low as 0.63%, whereas yogurt extracts began to show dose-dependent antiproliferative effects only at doses of at least 2.5%. Moreover, at a 2.5% dose, kefir extracts decreased the MCF-7 breast cancer cell numbers by 56%, while yogurt extracts decreased the breast cancer cells by only 14%. Extracts of kefir extracts had no observable antiproliferative effects in the normal HMECs, while the yogurt extracts had antiproliferative effects on HMECs at the 5% and 10% doses. Unfermented cow milk extracts increased proliferation of MCF-7 cells and HMECs at concentrations above 0.31%. Further analyses demonstrated that kefir-mediated milk fermentation resulted in an increase in peptide concentrations and a change in peptide profiles compared to yogurt or milk. The authors conclude that kefir extracts contain constituents that specifically inhibit the growth of human breast cancer cells.

Previous studies using a mouse model have demonstrated that Lactobacillus helveticus and Lactobacillus casei inhibit the development of fibrosarcoma and colon cancer, respectively. The present study was designed to evaluate the effects of the consumption of milk fermented by L. helveticus on a mouse model for mammary carcinoma. Female BALB/c mice were injected with American Type Culture Collection 4T1 tumoral cells in the left mammary gland after having been fed for two, five or seven consecutive days with fermented milk. Rate of tumor development, histological changes, apoptosis, phagocytic index, peritoneal macrophages, β-glucuronidase enzyme in peritoneal macrophages, γ-interferon (INFγ) and tumor necrosis factor-α (TNF-α) in blood serum, CD4+, CD8+, interleukin-6 (IL-6), IL-10, TNF-α and INFγ by immunoperoxidase, and β-glucuronidase activity in intestinal fluid all were monitored for two months. The administration of L. helveticus delayed the development of mammary tumor in every cases, a two- or seven-day feeding period being the most effective. The authors report that the effect was mediated by increased apoptosis and decreased production of pro-inflammatory cytokines, in particular IL-6, which is implicated in estrogen synthesis.

Phytoestrogens of the lignan type are widely distributed in plant food items; the richest known dietary source of lignans is flaxseed. The major flaxseed lignan are glycosides of secoisolariciresinol, however flaxseed also contains small amounts of matairesinol, isolariciresinol, and pinoresinol. Secoisolariciresinol (but none of the other lignans) has been identified in pumpkin seeds. In the present study, additional flaxseed and pumpkin seed lignan glycosides are identified. Lariciresinol was identified in flaxseed and in pumpkin seeds. The novel lignan demethoxy-secoisolariciresinol also was tentatively identified in flaxseed.

Previous studies have shown that compounds released during milk fermentation by Lactobacillus helveticus are implicated in the antitumor effect of this product. Here the effects of the consumption, during 2 or 7 days, of kefir or kefir cell-free fraction (KF) on the systemic and local immune responses in mammary glands and tumors using a murine hormone-dependent breast cancer model were studied. In the tumor control group, mice did not receive these products. At the end of the feeding period, mice were injected subcutaneously with tumor cells in the mammary gland. Four days post-injection, they received kefir or KF on a cyclical basis. Rate of tumor development, cytokines in serum; mammary gland tissue, and tumor isolated cells were monitored. Two-day cyclical administration of both products delayed tumor growth. Both kefir and KF increased IL-10 in serum and decreased IL-6(+) cells (cytokine involved in oestrogen synthesis) in mammary glands. Two-day cyclical administration of KF increased IL-10(+) cells in mammary glands and in tumors and decreased IL-6(+) cells in tumor. This study demonstrated the modulatory capacity of KF on the immune response in mammary glands and tumors and the importance of the administration period to obtain this effect.

The aim was to explore previous findings within the Malmo Diet and Cancer cohort (Sweden) that ω6-fatty acid intakes are positively associated with breast cancer risk among women 50 yr of age and older and specifically examine relations between breast cancer risk and fat from different food groups. Incident breast cancer cases (n = 237) were matched to controls (n = 673) on age and screening date. A modified diet history method, a structured questionnaire, and anthropometric measurements provided data. Fat-food variables from 24 food groups were computed. Conditional logistic regression examined breast cancer risk associated with energy-adjusted exposure categories of fat-food variables. Fat from fermented milk products was negatively associated with breast cancer risk (trend, P = 0.003). The highest quartiles of vegetable oil-based dietary fats (odds ratio, OR = 1.74; confidence interval, CI = 1.12-2.72) and dried soup powders (OR = 1.59; CI = 1.04-2.43) showed positive associations. Dietary fiber did not influence associations.