Studies suggest an association between nutrition and tumor development. Dietary patterns with foods rich in carbohydrates (PBA) and saturated fatty acids (PCS), represented by fructose (F) and palmitic acid (PA), are associated with the risk of breast cancer, although the cellular mechanisms are not clear. The objective was to evaluate the effects of diet on interactions of the tumor microenvironment, between cancer-associated fibroblasts (CAFs) and breast tumor cells, mediated by extracellular vesicles (EVs). Balb/c mice fed 2 months with PBA, PCS, or PBA+PCS were implanted s.c. with LM3 breast tumor cells. Tumors from mice on the PBA+PCS diet showed a higher frequency of CAFs, collagen and ultrastructural signs of increased EV secretion in transmission electron microscopy (TEM). Immunohistochemistry with CD63 revealed more intense and diffuse staining in the cell membrane, suggesting greater release of exosomes. In vitro, the mammary CAFs F88 cell line was stimulated with F40mM, AP250uM, F+AP or their vehicles for 24h. EVs were isolated from supernatants by sequential ultracentrifugation, characterized by MET and labeled with CD63 using immunogold. F+AP increased frequency of EVs of 20-30nm compared to controls or F and AP alone. MCF-7 tumor cells were stimulated for 24 h with F88 conditioned media treated with F, AP and F+AP and with F88 EVs treated equally. Conditioned media and F88 EVs treated with F+AP increased MCF-7 cell proliferation, determined by bromodeoxyuridine and cell count. This protumor action of EVs was inhibited by preincubating MCF-7 with genistein, suggesting clathrin-independent uptake. F88 EVs treated with F+AP decreased cell apoptosis, measured by annexin V flow cytometry in MCF-7 and MDA-MB-231 cells. These results indicate the pathogenic effect of dietary patterns rich in F and AP in the breast tumor microenvironment, through the release of pro-proliferative EVs