A review of the literature and clinical studies published in Cancer Therapy Advisor suggests there is currently no evidence that the use of multivitamins or general vitamin and/or antioxidant supplements reduces the risk of developing cancer.
With respect to the use of single vitamins or plant supplements, most of the studies conducted so far have not shown a definite link between their use and changes in cancer incidence. However, a meta-analysis of randomised controlled trials suggests that calcium supplements may reduce the risk of colorectal cancer, and vitamin D may reduce the risk of pancreatic cancer or blood cancer. Also, supplementation with folic acid may be protective against colorectal cancer for people with irritable bowel disease.
Overall, there is no clear, overarching evidence that food supplements or nutraceuticals can help prevent cancer.