All the latest studies point to pretty good proof that Vit D is important and helps keep the beast at bay:https://www.yalemedicine.org/stories/vi ... al-cancer/
"A group of 139 patients with metastatic colorectal cancer were prescribed standard chemotherapy and vitamin D supplements. One group received a high dose of vitamin D (8,000 international units [IU] daily for 14 days followed by 4,000 IU/day thereafter), and the other group was given low doses (400 IU, found in most multivitamins).
Dr. Fuchs and colleagues found that the 69 patients who received the high dosage of vitamin D experienced a 36 percent improvement in the rate of cancer progression or death when compared to the 70 patients who received low-dose supplements. Specifically, the length of time before the disease worsened was longer (a median time of 13 months) compared to those who were supplemented with lower doses, whose disease worsened after about 11 months.
“Our trial suggests that addition of high-dose vitamin D to chemotherapy for colorectal cancer can improve the effectiveness of our standard therapies,” says Dr. Fuchs. “Ultimately, this represents a relatively inexpensive intervention that could make a meaningful difference in the lives of people diagnosed with colorectal cancer.”
Vitamin D3, NOT D2
High Dose: 4000 to 8000 IU, NOT the useless 400-800 IU recommended by the US Institute of Medicine