This is a diet that involves eating flaxseeds mixed with one of several different milk products on a daily basis. In addition, it promotes eating a large number of vegetables, fruits, and other fresh foods. IT also promotes staying away from oily foods, sugar, and meat. 
While many people choose to use this diet when they are going through cancer treatment, there is no proof it is actually helpful. However, preliminary medical studies have indicated that flax seeds may help with stopping the growth of cancer cells. 
Below is a doctor speaking about the diet and when he would recommend using this protocol.
Reference 1: http://www.budwigcenter.com/the-budwig-diet/#.VcmMU_lLpko
Reference 2: http://www.cancerresearchuk.org/about-cancer/cancers-in-general/cancer-questions/what-is-the-budwig-diet