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Expert Analysis Highlights:
There’s a lot of controversy about the effects of Vitamin D on survival outcome for various forms of cancer, including breast, prostate and colorectal cancer. Several recent articles associating Vitamin D levels in the serum, as well as several large studies on Vitamin D supplements, have been published recently. Dr. Kathleen Wesa from Memorial Sloan Kettering Comprehensive Cancer Center described the results of a retrospective study that analyzed baseline Vitamin D levels in newly diagnosed Stage IV colorectal cancer to determine if serum levels at diagnosis could predict subsequent survival. The results were reported in Oncology News International (August, 2010). Interestingly, the majority of patients (83%) were Vitamin D deficient. The “take-home message” was that Vitamin D levels were significantly associated with survival and that patients with low Vitamin D levels had survival outcomes that were 1.5 times worse than those with normal levels. The authors concluded that most patients with newly diagnosed Stage IV colorectal cancer are Vitamin D deficient at the time of diagnosis and that higher Vitamin D levels are associated with better survival rates. A similar type of study by Dr. Mezawa and colleagues from Japan in colorectal cancer patients undergoing surgery found that higher Vitamin D levels at surgery were associated with a better survival rate.
What we don’t know from this study is whether an intervention with Vitamin D supplements would improve survival rates in those patients who are Vitamin D deficient. In other words, it’s one thing to find a correlation in the data through studies like the one above, but it’s a completely different reality sometimes when the conclusions we draw from the data are put to the test. In a study reported in the ASCO Post (October 2010), Dr. Kimmie Ng from the Dana-Farber Cancer Center in Boston reported that multivitamin supplementation during or after adjuvant chemotherapy failed to improve the outcomes in those with Stage III colon cancer who underwent surgical resection. Dr. Ng stated, “To our knowledge, this is the first study to examine the impact of multivitamin use on survival among patients with established colon cancer. No benefit on patient outcome was seen for multivitamin supplementation in this large prospective study of patients with Stage III colon cancer overall.”
But hold on before one makes a totally negative conclusion. In this study, they did identify an interaction between multivitamin use and age. Thus, patients aged 60 or younger appeared to derive benefit from the supplements. Moreover, less fatigue was observed in multivitamin users than in non-users. The interactions of multivitamin D used with younger ages will need to be explored in further studies.
A third large scale European study was reported this year that collected data on Vitamin D serum levels among 52,000 participants in several European countries. One object of the study was to determine whether there was a link between pre-diagnostic circulating Vitamin D levels and the risk for developing colorectal cancer. In a “case-control study”, the authors focused on 1,248 cases of colorectal cancer that developed after enrollment into the study and matched their results to the same number of healthy controls. The investigators found that lower levels of serum Vitamin D were associated with a higher colorectal cancer risk and conversely that higher concentrations of serum Vitamin D were associated with a lower colorectal cancer risk. However… and this is important … the investigators also found that a higher consumption of dietary Vitamin D was not associated with a reduced risk of colorectal cancer. They concluded that the optimal level of Vitamin D supplementation still needs to be established through clinical trials before any change is made to public health recommendations.
Trying to sort out the impact of a single factor in the survival outcome of a complex disease such as colorectal cancer is difficult. Nevertheless, the current evidence shows some interesting “clues” that patients who are deficient in serum Vitamin D have an increased risk for developing colorectal cancer and a worse outcome if they develop colorectal cancer later on. On the other hand, there is no evidence to date that taking Vitamin D supplementation as a treatment intervention improves the survival outcome. It would make sense, however, for us to take a regular dose of multivitamin supplementation (but not high doses) as part of good health. I do.