From MedscapeCME Clinical Briefs
News Author: Roxanne Nelson
CME Author: Désirée Lie, MD, MSEd
February 16, 2010 — The regular consumption of sugar-laden soft drinks could boost a person's risk of developing pancreatic cancer. The results of a new study found that individuals who consumed 2 or more soft drinks per week had an 87% increased risk for pancreatic cancer, compared with those who did not.
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
Clinical Context
Carcinoma of the pancreas has high metastatic potential and poor prognosis because of lack of good treatment options and late presentation, with a 5-year survival time of less than 5% and no specific primary preventive strategies available. Smoking, obesity, and diabetes mellitus have been reported as risk factors for pancreatic cancer. Also, high glycemic foods that may predispose to diabetes may predispose to pancreatic cancer.
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.
Study Highlights
The Singapore Chinese Health Study is a population-based, prospective cohort study of diet and cancer risk conducted in permanent residents from government-built housing estates where 86% of the population resided.
This study involved 2 dialect groups: the Hokkien and Cantonese originating from the southern part of China.
Participants were men and women aged 45 to 74 years without preexisting pancreatic cancer.
Recruitment was by letter, and staff went from door to door inviting participation with each subject.
A trained interviewer then interviewed the participants face-to-face using a structured scanner-readable questionnaire.
The interviewer asked subjects about demographics, lifestyle, diet, and medical history.
Diet was elicited with a semiquantitative 165-item food frequency questionnaire.
The questionnaire included commonly eaten food from Singapore, with 3 portion sizes and frequency in 8 categories ranging from never or hardly ever to 6 or more times daily.
Photographs of foods were presented to identify the food groups.
The questionnaire was validated against 24-hour recall in at least 1000 participants.
Soft drink portions were defined as 1 glass.
1 glass was designated as 237 mL and was equivalent to 1 cup.
Juices were categorized into specific drinks that included sugarcane, honeydew melon, apple, watermelon, carrot, pineapple, star fruit, and lemon juices.
The Singapore Food Composition Table was developed to analyze the nutritional content of food types.
Other risk factors for pancreatic cancer were assessed, including BMI, smoking, and physical activity.
Pancreatic cancer cases were ascertained by linkage to the population-based cancer registry and registry of births and deaths.
142 incident cases were identified, of which 56.4% were histologically confirmed, 38.8% were by clinical and radiologic findings, and 4.8% were identified by death certificates.
Rate of loss to follow-up was only 0.03%.
Mean age was 56 years, 55% were women, mean BMI was 23 kg/m2, 30% were ever-smokers, and 10% had type 2 diabetes.
At baseline, 9.7% of participants consumed at least 2 soft drinks per week and 10.2% consumed at least 2 servings of juice per week.
Those who consumed 2 or more soft drinks or juices weekly were likely to be younger, men, smoke, have higher levels of education, consume alcohol, and have higher energy intake and lower physical activity vs those who consumed no soft drinks or juices.
They also had a higher consumption of total carbohydrates, sugar, and red meat.
After 14 years and 648,387 person-years of follow-up, invasive exocrine pancreatic cancer developed in 140 persons .
Smokers had a 49% increased risk for pancreatic cancer.
BMI and a history of diabetes were not associated with an increased risk for pancreatic cancer.
Results for all risks were similar for men and women, and analysis was combined for the 2 sexes.
Drinking 2 or more soft drinks per week was associated with more than 80% increase in risk for pancreatic cancer after adjustment for other risks (HR, 1.87).
This risk was independent of diabetes and smoking and persisted after excluding those who had pancreatic cancer within 5 years of baseline.
After adjustment, juice intake of 2 or more drinks per week overall was not associated with increased risk, but when smokers were excluded, there was an association between juice intake and pancreatic cancer risk (HR, 1.60).
The authors concluded that soft drink consumption was positively associated with pancreatic cancer risk but that juice consumption was associated with risk among nonsmokers only.
Clinical Implications
Consumption of 2 or more soft drinks weekly is associated with an increased risk for pancreatic cancer in the Chinese population.
Consumption of 2 or more fruit drinks weekly is not associated with an increased risk for pancreatic cancer overall, but the risk is increased in nonsmokers.
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