Soft Drink Consumption Linked to Pancreatic Cancer

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.

Chocolate Linked to Lower Stroke and Stroke Mortality Risk

February 12, 2010 — Just in time for Valentine's Day, a new systematic review from Canadian researchers suggests higher chocolate consumption may be associated with a lower risk for incident stroke and stroke-related mortality.

Results of 2 prospective cohort studies showed, respectively, a 22% reduction in stroke risk for those who had 1 serving of chocolate per week and a 46% reduction in stroke mortality from weekly consumption of flavonoids in 50 g of chocolate vs no consumption. A third study showed no association between chocolate intake and stroke or death.
However, the number of studies looking at this relationship was small, senior author Gustavo Saposnik, MD, from St. Michael's Hospital and the University of Toronto, Canada, told Medscape Neurology. "We need more prospective studies that specifically identify the type of chocolate and the amount, including the amount of flavonoids included in the composition of the chocolate, to make more valid conclusions," he said.
The results were released February 11 in advance of their planned presentation at the upcoming American Academy of Neurology 62nd Annual Meeting in April. The abstract will post to http://www.aan.com on February 17.

Varying Effects
Chocolate contains cocoa butter, flavonoids, carbohydrates, and vitamins. Previous studies, most of them epidemiological, have shown varying effects of chocolate consumption on the risk for cardiovascular disease, the researchers, with first author Sarah Sahib, BScCA, from McMaster University in Hamilton, Ontario, Canada, write. "Less is known about the risk of stroke in association with flavonoid intake," they note.
To examine this association, the authors carried out a systematic review of studies published between 2001 and 2009, using search terms including flavonoids, flavanols, isoflavones, and anthocyanidins, as well as stroke and mortality.

"We found 88 publications, among them 3 prospective studies, and another retrospective study providing some information on the effect of chocolate consumption on the incident risk of stroke," Dr. Saposnik said. "Two of these studies show a reduction in the incident risk of stroke, and the other 2 didn't show any substantial difference."

For example, of the 3 prospective studies, 1 found no association between flavonoid intake and the risk for stroke or death when 3% of catechin intake came from chocolate (relative risk [RR], 0.92; 95% confidence interval [CI], 0.51 - 1.68).

However, a second study found a reduction in incident stroke for chocolate consumption once per week vs no consumption (RR, 0.78; 95% CI, 0.65 - 0.94).

The third study looked at the association between flavonoid intake and stroke mortality and found a suggestion of protection against stroke mortality from 50 g of chocolate (hazard ratio, 0.54; 95% CI, 0.30 - 0.96).

The authors conclude that further prospective studies are needed "to assess whether the benefit of chocolate-based flavonoid consumption truly lowers stroke risk, or whether the apparent benefit is biased by a healthy user effect."

Investigation a Challenge
However, although more data on this link would be helpful, Dr. Saposnik pointed to several challenges to doing these kinds of studies. First, it is important to document the actual content of flavonoids or other substances thought to be active in the chocolate being consumed.
"There are some studies that compare the content of flavonoids for different food elements and antioxidant capacity," he said. Dark chocolate is one with the highest flavonoids and procyanidins, which have been associated with lower cardiovascular risk, and in addition, dark chocolate has the highest antioxidant capacity.
Still, there are varying types of chocolate, and the amounts that are required to affect stroke risk may bring a load of sugar and fats that may work counter to the beneficial effects. "50g of chocolate per day is a significant amount," Dr. Saposnik notes.

Finally, large longitudinal studies are also expensive, and funding for them scarce, which may explain why much of the evidence is coming from epidemiologic studies, he added. One alternative may be to conduct smaller studies, looking the effects of consuming controlled amounts of chocolate on some intermediate biomarker of stroke risk.

The study received no commercial support. The authors have disclosed no relevant financial relationships.
 
American Academy of Neurology 62nd Annual Meeting. April 10-17, 2010. Published online February 11, 2009.