July 23, 2012 — Higher intakes of the antioxidants vitamin C, vitamin E, and selenium could possibly cut the risk of developing pancreatic cancer by up to 67%, according to a study published online today in Gut. Pancreatic cancer kills more than 250,000 people a year worldwide and has the worst survival rate of any tumor.
Paul J.R. Banim, honorary researcher in the Department of Medicine, University of East Anglia, Norwich, United Kingdom, and colleagues analyzed the histories of 23,658 people aged 40 to 74 years who entered the Norfolk group of the European Prospective Investigation of Cancer (EPIC) between 1993 and 1997 and compared them with the histories of 3970 control patients. The participants were Norfolk County residents registered with 35 general practices. On 10-year follow-up, 49 people (55% of whom were men) had developed pancreatic cancer, and on 17-year follow-up, 86 (44% men) had developed pancreatic cancer.
On entry into the study, participants completed 7-day food diaries, recording their dietary intakes the first day during a baseline health check with a nurse, who also took serum blood samples for analysis. The remaining 6 days, the participants recorded food intake at home, including information on food types, portion sizes, brands, cooking methods, and recipes for 8 meal times each day.
The participants returned their complete diaries to study headquarters, and trained nutritionists entered the data into a specifically designed computer program called Data Into Nutrients for Epidemiological Research (DINER). DINER matched each diary's entry with 1 of 11,000 food items and 55,000 portion sizes and converted the data into nutrient values. To investigate whether vitamin C, vitamin E, selenium, and zinc might lower the risk of developing pancreatic cancer, the researchers divided the nutrient intake amounts into quartiles and then compared the lowest-intake quartile with a summation of the 3 higher quartiles.
"Participants eating higher intakes of all of these micronutrients were 67% less likely to develop pancreatic cancer than those eating lower amounts," the researchers write. "For selenium, the effect size was large with an approximately halving of the risk with greater intakes, and for vitamin E, there was a slightly smaller effect of borderline statistical significance. For vitamin C, inverse associations were seen in the data from both the food diaries and serum, although only the latter was statistically significant." Genetics, smoking tobacco, and type 2 diabetes are known risk factors for pancreatic cancer, and antioxidants also may play a role by stimulating the immune system by inactivating free radicals and reducing oxidative stress, the researchers write.
The researchers used Cox proportional hazards regression modeling to estimate hazard ratios (HRs) at 10 years follow-up, with the lowest quartile as baseline. The researchers write,"[T]here were inverse associations between the lowest quartile and a summation of the three higher ones for selenium (HR=0.49, 95% [confidence interval (CI)] 0.26 to 0.93, p=0.03) and vitamin E (HR=0.57, 95% CI 0.29 to 1.09, p=0.09), but not vitamin C (HR=0.68, 95% CI 0.37 to 1.26, p=0.22) or zinc (HR=0.91, 95% CI 0.44 to 1.91, p=0.81)."
Individuals consuming the 3 higher quartiles of for all 3 dietary antioxidants, vitamin C, vitamin E, and selenium, had a decreased risk for pancreatic cancer (HR, 0.33; 95% CI, 0.13 - 0.84; P = .05).
"Based on these figures and if the association is causal, then 8.2% of all pancreatic cancers could be prevented by avoiding the combined lowest intakes of vitamins C and E and selenium," the researchers write.
"Participants eating higher intakes of all of these micronutrients were 67% less likely to develop pancreatic cancer than those eating lower amounts." If a causal association is confirmed in other studies, population-based dietary recommendations could reduce risk of pancreatic cancer, the researchers add.
The primary weakness of the study, the researchers note, was possible error in participants recording habitual diet and possible changes in diet patterns over time after study recruitment. Its primary strengths were its prospective design and the use of diaries for collection of data.
"In summary," the researchers conclude, "this prospective cohort study, using dietary antioxidant data, derived for the first time from food diaries, demonstrated inverse associations with total dietary antioxidant intake, selenium and vitamin E. A role for vitamin C was supported by the serum analysis with large effect sizes."
The study was funded by The Big C Cancer Charity, Norfolk. The authors have disclosed no relevant financial interests.
Gut. Published online July 23, 2012. Article
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