Greater flavonol intake associated with reduced pancreatic cancer risk
A presentation at the 2007 Annual Meeting of the American Association for Cancer Research held this month in Los Angeles reported the finding of researchers at the Cancer Research Center of Hawaii that diets high in plant compounds known as flavonols have a reduced rate of pancreatic cancer. Onions, broccoli, berries, kale, and apples among other plants provide high amounts of the compounds, which include kaempferol, quercetin and myricetin.
For the current investigation, Laurence Kolonel, MD, PhD and colleagues evaluated the diets of 183,518 residents of California and Hawaii who were participants in The Multiethnic Cohort Study. Subjects completed food questionnaires upon enrollment and were followed for an average of eight years. Five hundred twenty-nine participants developed cancer over the follow-up period.
The team found that participants who consumed the most flavonols had a 23 percent lower risk of developing pancreatic cancer than those whose intake was least. The benefit was greatest in smokers, who experienced a 59 percent lower risk of developing the disease if their flavonol intake was among the highest group according to intake. “The effect was largest in smokers, presumably because they are at increased pancreatic cancer risk already", stated research team member Ute Nöthlings, DrPH, who is now with the German Institute of Human Nutrition Potsdam-Rehbruecke. “Short of stopping tobacco use, it has been difficult to consistently show lifestyle factors that might help protect against this deadly cancer.”
The study is the first to prospectively examine classes of flavonols and pancreatic cancer risk. When individual flavonol intake was analyzed, kaempferol was associated with the greatest reduction.
“Anticarcinogenic effects of flavonoids in general have been attributed to the ability of these constituents to inhibit cell cycle, cell proliferation and oxidative stress, and to induce detoxification enzymes and apoptosis," Dr Nöthlings explained.
"Further epidemiological studies in other populations and geographic regions are needed to confirm our findings," she added.
Age, sex, race, and ethnicity. The disease is more common in the elderly and among men, and there is a higher incidence rate among African-Americans (Ghadirian L et al 2003).
Smoking (Lowenfels AB et al 2002; Michaud DS 2004).
Exposure to chemicals such as gasoline, petroleum products, and DDT (Alguacil J et al 2003; Hoppin JA et al 2000; Simon B et al 2001).
Inherited pancreatic disease and inherited breast cancer (Cowgill SM et al 2003; Ghadirian P et al 2003; Lowenfels AB et al 2004).
Chronic pancreatitis and diabetes mellitus (Truninger K 2000).
Insulin resistance (Berrington de Gonzalez A et al 2003).
Diet: excess calorie intake; high intake of saturated fats and oils, including omega-6 fatty acids, meat, and dairy products; and high intake of fried foods, carbohydrates, cholesterol, salt, nitrites from animal products, and nitrosamines (Coss A et al 2004).
Tea is particularly rich in polyphenols such as epigallocatechin gallate (EGCG) that act as antioxidants. Black and green tea extracts reduce pancreatic tumor cell growth by approximately 90 percent while preventing angiogenesis (Maiti TK et al 2003; Masamune A et al 2005; Roomi MW et al 2005). They also decrease the expression of the K-ras gene (Lyn-Cook BD et al 1999a) and the invasiveness of pancreatic cancer cells (Takada M et al 2002).
The active constituents in green tea are polyphenols, with an antioxidant called epigallocatechin-3-gallate (EGCG) being the most powerful. The antioxidant activity of EGCG is about 25-100 times more potent than vitamins C and E. One cup of green tea may provide 10-40 mg of polyphenols and has antioxidant effects that are greater than a serving of broccoli, spinach, carrots, or strawberries.