β-Sitosterol has recently been shown to induce G2/M arrest, endoreduplication, and apoptosis through the Bcl-2 and PI3K/Akt signaling pathways. β-Sitosterol, a main dietary phytosterol found in plants, may have the potential for prevention and therapy for human cancer. Although the exact mechanism of action of β-sitosterols is unknown, it may be related to cholesterol metabolism or anti-inflammatory effects (via interference with prostaglandin metabolism). β-Sitosterol induces apoptosis and activates key caspases in MDA-MB-231 human breast cancer cells.