Nutrient-based dietary patterns and pancreatic cancer risk
Introduction
Cancer of the pancreas is the fifth most common cause of cancer death in men and the fourth in women in Europe [1]. It has a very poor prognosis and it is among the few neoplasms for which mortality trends have not changed over the past 40 years in developed countries [2], [3], [4]. Although the etiology of pancreatic cancer remains largely unknown, recognized risk factors are tobacco smoking, heavy alcohol drinking, overweight/obesity, history of diabetes and chronic pancreatitis, and family history of the disease [5], [6].
With reference to dietary habits, several epidemiologic studies have reported an excess pancreatic cancer risk for high consumption of (red) meat and starchy foods/sweets, and a decreased risk for high consumption of fruit, vegetables, and folate-rich foods [7], [8], [9], [10], [11], [12], [13], although the evidence remains inconsistent [8], [14]. A limited number of studies have considered the role of combinations of foods and/or nutrients—identified through a priori scores or a posteriori–derived dietary patterns. In the U.S. prospective National Institutes of Health—AARP Diet and Health study, a nonsignificant 8% reduced risk of pancreatic cancer was found for high versus low no-alcohol Mediterranean dietary score, which became 27% comparing the most extreme categories of the dietary score [15]. A Canadian case-control study of 585 pancreatic cancer cases reported a 49% reduced risk for the fruit and vegetables pattern (characterized by high intake of fresh fruit and cruciferous vegetables) in men but not in women, and found no significant associations for the Western pattern (characterized by high intake of processed meat, sweets/desserts, refined grains, and potatoes) and the drinker pattern, characterized by elevated consumption of liquor, wine, and beer [16]. In a combined analysis of the Health Professionals Follow-up Study and the Nurses’ Health Study, including a total of 366 pancreatic cancer cases, no overall associations were reported with either the prudent pattern (characterized by high consumption of vegetables, legumes, fruit, whole grains, fish, and poultry) and the Western diet (characterized by high consumption of red and processed meat, refined grains, French fries, high-fat dairy products, sweets, desserts, and high-sugar drinks) [17]. A pattern characterized by high flavonol intake from tea, fruit, cabbage, and wine was found to be inversely related to the risk of pancreatic cancer in smokers in the Multiethnic Cohort including 610 pancreatic cancers, but not in the European Prospective Investigation into Cancer and Nutrition cohort, which included 517 cases [18]. In the Iowa Women's Health Study, which included 256 postmenopausal women with pancreatic cancer, no significant associations were found with any of the four dietary patterns identified, namely, the Mediterranean, the high fiber, the high fruit, and the high sweet [19].
To add further information on dietary patterns potentially associated to pancreatic cancer, we applied an exploratory principal component factor analysis (PCFA) on selected major nutrients derived from an Italian case-control study.
Section snippets
Methods
Between 1991 and 2008, we conducted a multicenter, case-control study on pancreatic cancer in the province of Pordenone and in the greater Milan area, northern Italy [12]. Cases were 326 patients (174 men and 152 women; median age, 63 years) with incident, confirmed pancreatic cancer, admitted to major teaching and general hospitals. Controls were 652 patients (348 men, 304 women; median age, 62 years), frequency matched to cases by study center, gender, and age (with a control to case ratio of
Results
The correlation matrix of the original nutrients was suitable for the factor analysis. Each nutrient showed at least 10 correlation coefficients greater than 0.30 in absolute value (data not shown), thus allowing to perform the analyses on the entire set of the selected nutrients. Results of Bartlett's test of sphericity (P < .001) allowed to reject the null hypothesis that the correlation matrix is an identity matrix (Appendix Table). The Kaiser–Meyer–Olkin statistic was 0.85, indicating that
Discussion
In the present analysis, we identified four dietary patterns that explain 75% of the total variance in nutrient intake in this Italian population. The animal products pattern, highly correlated with meat, cheese, and milk consumption, and the starch rich pattern, with a high correlation with bread, pasta, and rice intake, were significantly associated with an increased pancreatic cancer risk, whereas the vitamins and fiber pattern, positively correlated with various vegetables, legumes, and
Acknowledgment
This work was conducted with the contribution of the Italian Association for Cancer Research (AIRC, N. 10068 and 10415) and the Italian Ministry of University, Education and Research (PRIN 2009 X8YCBN). F. T. was supported by a fellowship from the Italian foundation for cancer research (FIRC). F.B. was supported by a fellowship of the “fondazione umberto veronesi”. The authors thank Mrs. Ivana Garimoldi for editorial assistance.
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