LOS ANGELESThere's nothing new about the value of eating lots of fruits and vegetables, but the effect of this diet on cancer risk has been difficult to show. At the 2007 American Association of Cancer Research annual meeting, however, several large-scale studies linked consumption of these healthful foods with significant reductions in several types of cancer.
A diet high in flavonols may help reduce pancreatic cancer risk, especially in smokers, according to the Multiethnic Cohort Study of 183,518 residents of California and Hawaii (abstract 856). Flavonols are ubiquitous in plant-based foods, but concentrations are highest in onions, apples, berries, broccoli, and kale.
Subjects were recruited to the prospective study, conducted at the Cancer Research Center of Hawaii, Honolulu, between 1993 and 1996 and answered dietary frequency questionnaires. After 8 years of follow-up, 529 participants developed pancreatic cancer. The intake of total flavonols was compared for these subjects vs those without pancreatic cancer, calculated by quintiles according to a multivariate Cox regression model.
Adults who consumed the largest amounts of flavonols had a 23% reduction in the risk of developing pancreatic cancer, compared with those who ate the least (P = .046). Smokers gained the most benefit, with those in the highest quintile reducing their risk by 59%, "perhaps because they are at increased pancreatic cancer risk already," said principal investigator Ute Nothlings, DrPH, who is now at the German Institute of Human Nutrition Potsdam-Rehbruecke. Smoking, the only established risk factor for pancreatic cancer, doubles the risk of the disease, compared to never smoking.
Among three individual flavonols that were evaluated, kaempferol (found in spinach and some cabbages) was associated with the greatest protection, a 73% reduction of risk in smokers and a 22% reduced risk overall.
Across quintiles of intake, total flavonols, and the individual compounds quercetin (found in onions and apples), kaempferol, and myricetin (found in red onions and berries), were all associated with a significant trend toward reduced pancreatic cancer risk in current smokers but not in never smokers or former smokers. The interaction with smoking status was significant for total flavonols, quercetin, and kaempferol, she said.
Interestingly, smokers fell mainly into the lowest quintile of flavonol intake, yet had the most benefit. The highest quintile of intake contained the lowest percentage of smokers, Dr. Nothlings said.