The VITAL trial  “was well designed, ” said Dr. Kramer.  “And when it is important to get the answer right-that is, when you’re potentially making recommendations to hundreds of thousands, or even millions, you want to make sure that your recommendations are based on very strong evidence,” he added.  Other research into vitamin D and cancer prevention is ongoing, such as studying whether some types of cancer may be more sensitive than others to the effects of supplementation.  For example, an NCI-sponsored clinical trial is currently looking whether supplementation with vitamin D, calcium, or both can prevent the development of new colorectal adenomas in people who have already had one or more such precancerous growths removed. VITAL will also examine effects of the supplements on the risk of new colorectal adenomas.  Dr. Manson and her colleagues would like to study the potential influence of genetics on the effects of vitamin D supplementation.   Source NCI  Berry Kramer, M.D. & JoAnn Manson, M.D.