Dietary factors modifying breast cancer risk and relation to time of intake.

Multiple factors contribute to the development of human breast cancer. However, environmental factors, especially dietary factors, appear to have the greatest effects. Evidence obtained in epidemiological studies has been corroborated by laboratory findings. Dietary components strongly associated with breast cancer include fat and phytochemicals. A diet high in n-3 polyunsaturated fatty acid (PUFA) or monounsaturated fatty acid (MUFA) and low in n-6 PUFA is protective against breast cancer. Some phytochemicals present in fruits and vegetables are also protective. Time of intake appears to be important: lifetime protection may be achieved if one is exposed to a dietary factor that lowers breast cancer risk early in life. Synergistic and antisynergistic interactions between dietary factors can modify breast cancer risk. The available evidence suggests that breast cancer risk can be reduced by early dietary intervention.