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- Vitamin D
Combating Colorectal Cancer
Vitamin D's effects in reducing cancer risk have been studied most extensively in colorectal cancer, the second leading cause of cancer death in the US. A study in 2005 investigated the relationship between vitamin D intake, serum vitamin D levels, and colorectal cancer risk. Individuals with vitamin D intake of 1000 IU or more daily or with serum vitamin D (25-hydroxyvitamin D) levels of 33 nanograms per milliliter (ng/mL) experienced a 50% lower risk of colorectal cancer.
A daily dose of 1000 IU of vitamin D is half the safe upper limit established by the National Academy of Sciences. According to the study authors, prompt public health action is needed to increase daily intake of vitamin D to 1000 IU and to raise serum levels of 25-hydroxyvitamin D. For some individuals, modest sunlight exposure may help achieve these optimal levels.
An epidemiological review conducted in 2005 at Harvard Medical School corroborated vitamin D's protective effects against colorectal cancer and noted that typical dietary intake of 200-400 IU per day is probably too low to confer appreciable benefits. The Harvard study noted that a person's vitamin D status at the time of cancer diagnosis and treatment may influence survival.
In the recent Polyp Prevention Trial, investigators analyzed several dietary factors in relation to the recurrence of adenomatous polyps in the colon. Adenomatous polyps are considered pre-malignant and may therefore be a harbinger of colon cancer. Low intake of calcium and vitamin D was associated with increased risk of recurrence of the pre-malignant polyps. Optimal vitamin D and calcium status may thus be an important preventive strategy against colon cancer.
CANCER CONSULTANTS STUDY - Vitamin D May Reduce Colorectal Cancer Mortality
Researchers from the National Institutes of Health have reported that higher circulating vitamin D levels may reduce the risk of death from colorectal cancer.
The details of this study appeared in the Journal of the National Cancer Institute
The relationship between vitamin D intake and blood levels and cancer incidence and mortality is complex. Several studies have shown that increased doses or high levels of vitamin D are associated with a lower risk of developing colorectal and breast cancer. However, not all studies have confirmed these observations.
To explore the relationship between levels of vitamin D in the blood and cancer mortality, researchers evaluated information from the Third National Health and Nutrition Examination Survey. The study collected information from more than 16,000 individuals.
Vitamin D levels were measured in blood samples collected at the start of the study. Men, Caucasians, and more educated people tended to have higher vitamin D levels. Individuals with a higher body mass index (BMI) tended to have lower vitamin D levels. The analysis accounted for these and other factors.
During follow-up, 536 cancer deaths occurred among study participants. Of these deaths, 153 were due to lung cancer, 66 were due to colorectal cancer, 72 were due to other digestive cancers (esophagus, stomach, liver, and pancreatic), 28 were due to breast cancer, 47 were due to prostate cancer, 40 were due to lymphoma or leukemia, and 130 were due to other types of cancer.
Total cancer mortality did not vary by level of vitamin D.
Colorectal cancer mortality was lower among individuals with higher vitamin D levels. Compared with individuals with serum vitamin D levels below 50 nmol/L, individuals with levels of 80 nmol/L or higher were 72% less likely to die of colorectal cancer.
These results suggest that vitamin D may reduce colorectal cancer mortality, but not total cancer mortality.
A potential limitation of this study is that vitamin D level was measured at only a single point in time. This single measure may not be a good indicator of vitamin D levels over time. Furthermore, the relatively small number of cancer deaths limited the ability of the researchers to evaluate individual types of cancer.