Even after taking factors such as smoking, caloric intake, and type 2 diabetes mellitus into account, the authors found that consuming soft drinks might play an independent role in the development of pancreatic cancer.
The finding is reported in the February issue of Cancer Epidemiology, Biomarkers & Prevention.
Both soft drinks and fruit juices have a high glycemic load relative to other foods and drinks, and it has been hypothesized that both are risk factors for pancreatic cancer. The high levels of sugar can increase levels of insulin in the body, and this can contribute to pancreatic cancer cell growth, the researchers explain.
Association Not Seen With Fruit Juice
However, this study did not find an association between consumption of juice and an increased risk for pancreatic cancer.
"There are several plausible explanations why fruit juice was not significantly associated with pancreatic cancer," said first author Noel Mueller, MPH, a research associate at Georgetown University Medical Center in Washington, DC.
One reason is that the finding was based on a relatively small number of cases, so there might have been too few cases to detect an effect with fruit juice, he explained. Another is that there are differences between soft drinks and fruit juice — fruit juice is lower in sugar, includes many nutrients, and is typically served in smaller portion sizes.
A third explanation is that fruit juice intake is associated with healthier lifestyle characteristics than soft drink intake, he said.
The consumption of soft drinks coincided with a number of other unhealthy lifestyle characteristics, making it somewhat difficult to separate smoking, caloric intake, body weight, and type 2 diabetes mellitus from soft drink consumption. "But the findings from our study suggest that soft drinks may play an independent role in the development of pancreatic cancer," Mr. Mueller told Medscape Oncology.
"The influence of soft drink intake on the risk of pancreatic cancer remained virtually unchanged after adjustment for smoking status, energy intake, body weight, and type 2 diabetes mellitus," he added.
Results Statistically Significant for Soft Drinks
The current study examined the association between the consumption of soft drinks and juice and the risk for pancreatic cancer among Chinese people residing in Singapore. The data came from the Singapore Chinese Health Study (n = 60,524), and information regarding the consumption of soft drinks, juice, and other dietary items, along with lifestyle factors and environmental exposures, was collected at recruitment to the study. The participants were followed for up to 14 years.
At the start of the study, 9.7% of the participants consumed at least 2 soft drinks per week and 10.2% consumed at least 2 servings of juice per week. The authors note that, compared with those who did not consume soft drinks, those who consumed 2 or more soft drinks per week were younger, were more likely to be men, and were more likely to smoke cigarettes. They also had higher levels of education, alcohol consumption, and total energy intake; lower levels of physical activity; and consumed more total carbohydrates, fat, added sugar, and red meat.
Individuals who reported consuming 2 or more juice drinks a week had lifestyle and dietary habits that were similar to those who consumed soft drinks. However, there was no association between juice intake and cigarette smoking, and body mass index (BMI) was comparable across different categories of soft drink and juice consumption.
At 14 years and a cumulative 648,387 person-years of follow-up, 140 incident pancreatic cancers developed in people who were cancer free at baseline. After adjustment for confounders such as BMI, type 2 diabetes mellitus, and fruit juice intake, the authors found that those consuming 2 or more soft drinks per week experienced a statistically significant increased risk for pancreatic cancer (hazard ratio [HR], 1.87; 95% confidence interval [CI], 1.10 - 3.15).
Although people who consumed 2 or more juice drinks a week had an increased risk for pancreatic cancer of approximately 30%, elevated HR was not statistically significant after adjustment for variables.
However, in an age-adjusted analysis, smoking was also a risk factor. After excluding former smokers, the authors found that current smokers had a 49% increased risk for pancreatic cancer, compared with never smokers (HR, 1.49; 95% CI, 0.98 - 2.27). This risk factor remained unaffected after adjustment for diabetes and BMI.
Can Be Extrapolated to United States and Europe
Singapore is a highly industrialized nation with lifestyle and nutritional patterns reminiscent of many westernized countries. In that sense, these findings could be extrapolated to the United States and Europe, explained Mr. Mueller. Soft drinks are the leading source of added sugar in the American diet, the authors note.
"However, there are inherent differences between Singaporean Chinese and Caucasians, which is why one must be cautious when generalizing these results to the United States and Europe," he said. "But it is important to note that other studies in Caucasian populations have suggested that soft drink intake may increase risk for pancreatic cancer."
Because pancreatic cancer is a relatively rare disease, the number of cases in this study was relatively small, the authors point out. This limited the statistical power of the study. Another limitation was the inability to collect repeated dietary measurements during the course of the study; therefore, they could not account for changes in consumption of soft drinks and juices.
However, this study adds to the evidence that soft drink consumption plays a role in the development of pancreatic cancer, they conclude, and that "clinical studies examining biomarkers for glycemia and insulinemia and taking a mechanistic approach to the question of soft drink consumption and pancreatic cancer are warranted."
There is "still much to understand on the link between sugar-sweetened beverages and pancreatic cancer," the authors write.
The study was supported by a grant from the National Cancer Institute. The researchers have disclosed no relevant financial relationships.
Cancer Epidemiol Biomarkers Prev. 2010;19;447-455. Abstract
This is a prospective, 14-year cohort study of Chinese people living in Singapore to examine the association between consumption of soft drinks and fruit juice and the risk for the development of pancreatic cancer.
Questions answered incorrectly will be highlighted.
In this study by Mueller and colleagues, which of the following factors is most likely to be associated with an increased risk for pancreatic cancer?
( )Consumption of 2 or more soft drinks weekly
( )Increased BMI
( )History of type 2 diabetes
( )Consumption 1 or more servings of red meat daily
Which of the following patients is most likely to be at risk for pancreatic cancer?
( )Smoker consuming 1 fruit drink per week
( )Nonsmoker consuming 3 fruit drinks per week
( )Male smoker consuming 1 fruit drink per week
( )Female smoker consuming 2 fruit drinks per week
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