The vitamin D council on using Vitamin D to help fight cancer

Bowel cancer is one of the 17 or so sun sensitive cancers that thrive in bodies with low vitamin d status.

Your vitamin d status at the time of diagnosis and treatment affects the outcome

It follows that the sooner you have an adequate higher status the better your prognosis is likely to be.

I should also point out that correcting 25(OH)D status is in addition to eating a low carb diet and conventional treatment.