Consumption of Vitamin D tablets was found to cut the risk of pancreatic cancer nearly in half, according to a study led by researchers at Northwestern and Harvard universities.
The findings point to Vitamin D's potential to prevent the disease, and is one of the first known studies to use a large-scale epidemiological survey to examine the relationship between the nutrient and cancer of the pancreas. The study, led by Halcyon Skinner, Ph.D., of Northwestern, appears in the September issue of Cancer Epidemiology Biomarkers & Prevention.
The study examined data from two large, long-term health surveys and found that taking the U.S. Recommended Daily Allowance of Vitamin D (400 IU/day) reduced the risk of pancreatic cancer by 43 percent. By comparison, those who consumed less than 150 IUs per day experienced a 22 percent reduced risk of cancer. Increased consumption of the vitamin beyond 400 IUs per day resulted in no significant increased benefit.
"Because there is no effective screening for pancreatic cancer, identifying controllable risk factors for the disease is essential for developing strategies that can prevent cancer," said Skinner.
"Vitamin D has shown strong potential for preventing and treating prostate cancer, and areas with greater sunlight exposure have lower incidence and mortality for prostate, breast, and colon cancers, leading us to investigate a role for Vitamin D in pancreatic cancer risk. Few studies have examined this association, and we did observe a reduced risk for pancreatic cancer with higher intake of Vitamin D."
Skinner, currently in the Department of Population Health Sciences at the University of Wisconsin School of Medicine and Public Health, and his colleagues analyzed data from two long-term studies of health and diet practices, conducted at Harvard University. They looked at data on 46,771 men aged 40 to 75 years who took part in the Health Professionals Follow-up Study, and 75,427 women aged 38 to 65 years who participated in the Nurses' Health Study. Between the two studies, they identified 365 cases of pancreatic cancer. The surveys are considered valuable for their prospective design, following health trends instead of looking at purely historical information, high follow-up rates and the ability to enable researchers like Skinner to incorporate data from two independent studies.
Pancreatic cancer is a rapidly fatal disease and the fourth-leading cause of death from cancer in the United States. This year, the American Cancer Society estimates that 32,000 new cases of cancer will be diagnosed. About the same number of people will die this year from the disease. It has no known cure, and surgical treatments are not often effective. Except for cigarette smoking, no environmental factors or dietary practices have been linked to the disease.
In addition to Vitamin D, the researchers also measured the association between pancreatic cancer and the intakes of calcium and retinol (Vitamin A). Calcium and retinol intakes showed no association with pancreatic cancer risk, although retinol is an antagonist of Vitamin D's ability to influence mineral balances and bone integrity.
For that reason, further research is necessary to determine if Vitamin D ingestion from dietary sources, like eggs, liver and fatty fish or fortified dairy products, or through sun exposure might be preferable to multi-vitamin supplements, which contain retinol.
The potential benefits of vitamin D for pancreatic cancer were only recently established by other laboratory studies. Normal and cancerous pancreas tissue contain high levels of the enzyme that converts circulating 25-hydroxyvitamin D into 1,25-dihydroxyvitamin D, the vitamin's active form. Other studies have shown an anti-cell proliferation effect of 1,25-dihydroxyvitamin D, potentially inhibiting tumor cells.
"In concert with laboratory results suggesting anti-tumor effects of Vitamin D, our results point to a possible role for Vitamin D in the prevention and possible reduction in mortality of pancreatic cancer. Since no other environmental or dietary factor showed this risk relationship, more study of Vitamin D's role is warranted," Skinner said.
Skinner's colleagues in the study include Dominique Michaud, Edward Giovannucci, Walter Willett and Graham Colditz of Harvard, and Charles Fuchs of the Dana-Farber Cancer Institute.
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