Vitamin D Linked to Reduced Pancreatic Cancer
A ray of hope for pancreatic cancer?
Posted 9/13/2006 7:52 PM ET
By Liz Szabo, USA TODAY
Researchers are exploring whether vitamin D might prevent pancreatic cancer, one of the deadliest malignancies.
Doctors say patients urgently need better ways to prevent and treat the disease, which strikes 33,730 Americans each year and kills 32,300, according to the American Cancer Society.
In a study published in the September issue of Cancer Epidemiology, Biomarkers & Prevention, doctors compared pancreatic cancer rates between people who consumed the most vitamin D - at least 600 international units a day from food and supplements - and those who consumed the least, or fewer than 150 international units.
The high vitamin D group had a rate of 12.5 pancreatic cancers per 100,000 people, about 40% lower than among people with the smallest intake, whose rate was 21.2 per 100,000 people, says the study's main author, Halcyon Skinner of the University of Wisconsin School of Medicine and Public Health.
Researchers examined two studies in which doctors have observed a total of more than 122,000 men and women for 16 years. It's possible that something else in diet or lifestyles may have affected risk, according to the study financed by the National Cancer Institute.
This type of trial is not designed to prove whether vitamin D really causes lower cancer rates, Skinner says. To do that, doctors would need to randomly assign patients to take vitamin D and compare them with another group assigned to an alternate regimen.
In a follow-up study, doctors plan to examine the levels of vitamin D in blood samples, says Charles Fuchs, an author of the study and associate professor at Boston's Dana-Farber Cancer Institute. That may provide a fuller picture, because people also get vitamin D from sunlight. Though this study does not provide enough evidence to recommend taking vitamin supplements, Fuchs says, people can reduce their risk by exercising, staying slim and avoiding tobacco, which may cause 25% of pancreatic cancers.
Vitamin D Linked to Reduced Pancreatic Cancer Risk
By Jeff Minerd, Contributing Writer, MedPage Today
Reviewed by Zalman S. Agus, MD; Emeritus Professor at the University of Pennsylvania School of Medicine.
September 13, 2006
good sources of vitamin D include fortified dairy products; fatty fish such as salmon, mackerel, or sardines; eggs; liver; and fortified breakfast cereals.
CHICAGO, Sept. 13 -- The risk of pancreatic cancer, already low, may be cut by as much as 41% by consuming the U.S. recommended daily allowance of vitamin D (400 IU), according to an epidemiologic cohort study of more than 100,000 people.
The protective effect held whether individuals got their vitamin D from dietary sources (such as skim milk and fatty fish), vitamin supplements, or a combination of both, found Halcyon G. Skinner, Ph.D., of Northwestern University here, and colleagues.
"To our knowledge, this is the first epidemiologic report of an association between vitamin D intake and the risk for pancreatic cancer," Dr. Skinner and colleagues wrote in the September issue of Cancer Epidemiology Biomarkers & Prevention.
Previous studies that found reduced risk for colon, breast, and prostate cancer in people living in sunny climates suggested there might be a link between vitamin D and pancreatic cancer as well, the investigators said. Pancreatic cancer is the fourth leading cause of cancer deaths (about 32,000) in the United States.
The current study analyzed data from more than 46,000 men (ages 40 to 75) who took part in the Health Professionals Follow-up Study (HPFS). The analysis also included data from more than 75,000 women (ages 38 to 65) involved in the Nurse's Health Study. Both the men and the women took a food frequency questionnaire in the mid 1980s. Average follow-up was 16 years.
After adjusting for vitamin use, smoking, diabetes, and other risk factors, those whose vitamin D intake was greater than 150 IU/day had reduced pancreatic cancer risk compared with those whose intake was less:
* 150-299 IU: relative risk=0.78 (95% confidence interval=0.53 to 1.14)
* 300 to 449 IU: RR=0.57 (95% CI=0.40 to 0.83)
* 450 to 599 IU: RR=0.56; (95% CI=0.36 to 0.87)
* 600 IU or more: RR=0.59 (95% CI=0.40 to 0.88)
The results were weaker when multivitamin supplement users were excluded. In this analysis, those who consumed 300 IU/day or greater from diet alone had a nonsignificant 33% reduced risk compared with those whose intake was less (RR=0.67; 95% CI=0.41 to 1.09; P=0.09).
However, the extremely small sample of non-vitamin supplement users (n=199) renders these results less than reliable, the investigators said.
After adjusting for vitamin D intake, the study found no protective effect for calcium (P=0.29) or retinol (P=0.43).
However, intake of two foods that are a rich source of vitamin D, skim milk and fatty fish (such as salmon, mackerel, or sardines), were independently though non-significantly associated with reduced risk.
Compared with those who never drank skim milk, the relative risk for those who drank more than one 8-ounce serving per day was 0.83 (95% CI=0.63 to 1.10). Similarly, the relative risk for those who ate more than one three- to five-ounce serving of fatty fish per week was 0.78 (95% CI=0.55 to 1.11).
Laboratory studies have suggested that vitamin D might reduce pancreatic cancer risk by regulating cellular proliferation and differentiation. Normal and malignant pancreatic tissue expresses high levels of an enzyme that converts 25-hydroxyvitamin D to active 1,25-dihydroyxvitamin D, which has an antiproliferative effect on pancreatic cancer cell lines, the researchers noted.
A main limitation of the study is that it did not account for the cutaneous production of vitamin D, the authors said.
"In concert with laboratory demonstrations of antitumor effects of vitamin D, our results point to a potential role for the vitamin D pathway in the prevention and pathogenesis of pancreatic cancer," the authors said.
"Considering the paucity of epidemiologic data on this malignancy, additional study of vitamin D and pancreatic cancer is warranted," they concluded.
Primary source: Cancer Epidemiology Biomarkers & Prevention
Halcyon Skinner et al. "Vitamin D intake and the risk for pancreatic cancer in two cohort studies." Cancer Epidemiology Biomarkers & Prevention 2006; 15:1688-1695.
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