(NaturalNews) A study led by Kimmie Ng, M.D., M.P.H., of the Dana-Farber Cancer Institute has found that colorectal cancer sufferers with high levels of vitamin D had better survival rates during a follow-up period when compared to those with low levels of the vitamin. The study also involved the Harvard School of Public Health, Brigham and Women's Hospital and the Medical University of South Carolina.
These findings are significant because, while previous research have shown a link between vitamin D levels and colorectal cancer occurrence, this study actually establishes correlation between levels of vitamin D in the blood with survival among persons who have already developed colorectal cancer.
Methodology and Details
The study, reported in a June issue of the Journal of Clinical Oncology, looked at data pertaining to 304 persons who had participated in the Nurses' Health Study (NHS) and the Health Professionals Follow-Up Study (HPFS) -- these studies monitored the health of participants for many years.
The 304 persons had been diagnosed with colorectal cancer from 1991 to 2002 and also had their blood vitamin D levels measured at least two years before their cancer diagnoses.
The patients were categorized into four quartiles according to the measured levels of 25-hydroxy vitamin D3 (25(OH)D) levels in their blood -- top 25%, next 25%, and so on. 25(OH)D levels in the blood reflect the body's store of all sources of vitamin D, including that from diet, supplements, as well as that synthesized by the body after exposure to sunlight. The patients were then observed till January 2005 (for the HPFS) or June 2005 (for the NHS), or until they passed away, whichever took place first.
During the follow-up period, 123 persons passed on, with the cause of death being colon cancer or rectal cancer for 96 of them.
The study found that persons in the top quartile -- in other words those with the highest measured levels of vitamin D in their blood -- were 48% less likely to die in the follow-up period than those in the bottom quartile. This figure relates to death from any cause. With specific regard to colorectal cancer, the reduction in risk was found to be 39%. This is a significant relationship.
The results remained largely unchanged even after the exclusion of patients who were diagnosed within 5 years of having their blood samples collected.
The study, partly supported by grants from the National Cancer Institute, concluded that "among patients with colorectal cancer, higher pre-diagnosis plasma 25(OH)D levels were associated with a significant improvement in overall survival".
And the protective effects of vitamin D are not restricted to colorectal cancer. For example, a study on non-small-cell lung cancer (NSCLC) reported in the Journal of Clinical Oncology in Feb 2007 concluded that "vitamin D may be associated with improved survival of patients with early-stage NSCLC, particularly among stage IB-IIB patients".
The nature of the study could make its findings limited in some ways. For example, the sample size of the study, especially those who did die from colorectal cancer, was relatively small.
There were also variations in the time period between the point of vitamin D measurement and cancer diagnosis. In addition, information on the treatment taken by the cancer patients was not taken into account.
Then, there may be related factors which could contribute to the difference in survival rates. For example, those with higher vitamin D levels in their blood also tended to be physically more active.
However, even after physical activity, body-mass index (BMI) and other factors which influence cancer survival were controlled, the association between higher levels of vitamin D and better survival rates was still independently significant.
Thus, all in all, despite these limitations, the findings of the study are still important.
Previous Studies on Vitamin D and Prevention of Colorectal Cancer
The role of vitamin D in battling colorectal cancer becomes more pronounced when we consider its protective effects against the disease. As mentioned earlier, numerous other studies have already shown vitamin D to have a preventative effect on colorectal cancer.
For example, a pooled analysis of the results of five previous serum studies carried out by the University of California, San Diego in 2006 concluded that 'the evidence to date suggests that daily intake of 1000-2000 IU of vitamin D(3) could reduce the incidence of colorectal cancer with minimal risk'.
In Jan 2007, the American Journal of Epidemiology reported the findings of a multi-ethnic study which "support the hypothesis of protective roles for calcium, vitamin D, and dairy products in the risk of colorectal cancer".
Another study conducted by the National Cancer Center in Tokyo, Japan and published in July 2007 suggested that "a low level of plasma 25(OH)D may increase the risk of rectal cancer".
Should Cancer Patients load up on Vitamin D?
Investigators involved in the NHS / HPFS study feel that it is premature to recommend vitamin D supplements as part of cancer treatment. Dr. Ng has advised that current sufferers of the disease should consult their doctors regarding vitamin supplementation, and she suggested that future studies should look at the use of vitamin D supplements by colorectal cancer patients.
Sources of Vitamin D
The truth is, there are some studies which suggest that dietary vitamin D does not significantly lower the risk of colorectal cancer. However, according to "A Critical Review of Studies on Vitamin D in Relation to Colorectal Cancer", authored by William B. Grant and Cedric F. Garland, the likely reason for this is that "dietary sources provide only a portion of total vitamin D, with supplements and synthesis of vitamin D in the skin in association with solar UV-B radiation providing the balance".
Further, in "Do sunlight and vitamin D reduce the likelihood of colon cancer?", Cedric F Garland and Frank C Garland state that "the strong inverse association of sunlight and colon cancer raises the possibility that vitamin D, which prevents rickets, may also act in the prevention of colon cancer".
How do all these add up?
Colorectal cancer is today one of the major causes of death in the United States and many first world countries. Somewhat surprisingly, though, relatively little research has thus far looked into the impact of lifestyle factors on the survival prognosis of colorectal cancer patients. This includes lifestyle habits both during active cancer treatment as well as after.
With the health benefits and immune-boosting effects of sunshine and vitamin D well-documented, there is really no need to wait for bigger and better designed studies to empirically prove that vitamin D forms a useful part of the arsenal against colorectal cancer. Instead, as part of an overall healthy lifestyle, it is an extremely good idea to spend some time out in the open, without sunscreen, to enjoy moderate sun exposure.
Throw in some exercise -- according to the Textbook of Cancer Epidemiology, physical activity is also linked to better survival rates from several types of cancer, including colorectal cancer -- and we have got a much more potent mix in the battle against colon and rectal cancers.