The plant compound quercetin has shown promise as a possible treatment for and and preventative agent against lung cancer. The potentially beneficial activity of quercetin could stem from its antioxidant activity or could be due to direct action the compound takes within cells. Although no clinical trials have investigated the potential link between lung cancer and quercetin, epidemiologic studies and laboratory results indicate that the compound deserves further research.
Quercetin
Quercetin is a flavonoid phytochemical synthesized by plants and found in a wide range of foods, including apples, tomatoes, green leafy vegetables, onions, grapes and berries. It is also available as a dietary supplement in pill or capsule form. Quercetin supplements sometimes also include the enzyme bromelain. Upon consumption, quercetin appears to act as an antioxidant and provide anti-inflammatory activity within the body. In addition to lung cancer, quercetin has also been linked to the prevention and treatment of other types of cancer, cardiovascular disease and other disorders.
Lung Cancer Laboratory Studies
A 2005 study in the journal "Drug Metabolism and Disposition" found that quercetin glucuronides, a metabolite produced in the body from dietary quercetin, halts the growth and induces apoptosis, or cell death, of lung tumor cells in laboratory settings. Another study published in a in 2002 issue of the journal "Nutrition and Cancer" identified quercetin as the molecule responsible for inhibiting DNA damage caused by cooking oil fumes that could lead to lung cancer.
Epidemiological Evidence
Controlled clinical trials involving humans are lacking, but epidemiologic studies looking at quercetin's effect on lung cancer have produced promising data. Research published in 2002 in the "American Journal of Clinical Nutrition" presented evidence showing that men with the highest dietary intake of quercetin got lung cancer less often than those with lower intakes of this flavonoid. The study included more than 10,000 men and women who estimated their quercetin and other flavonoid intakes based on the content of these compounds in the foods the participants reported consuming.
Considerations
Taking quercetin supplements is unlikely to be useful in the prevention and treatment of lung cancer, even if a definitive link is found in future clinical trials. If quercetin does fight lung cancer, it probably works in synergy with other compounds, such as other flavonoids or antioxidant vitamins. However, foods high in quercetin tend to be nutritious and safe. The potential protection from lung cancer may offer an added benefit if you include them in your diet.
References
- Linus Pauling Institute: Flavonoids
- American Cancer Society: Quercetin
- University of Maryland Medical Center: Quercetin
- "Drug Metabolism and Disposition": Inhibition of lung cancer cell growth by quercetin glucuronides via G2/M arrest and induction of apoptosis. Yang J. H., et al. Feb 2005
- "American Journal of Clinical Nutrition": Flavonoid intake and risk of chronic diseases. Knekt P., et al. Sept. 2002
- "Nutrition and Cancer": Protection by quercetin against cooking oil fumes-induced DNA damage in human lung adenocarcinoma CL-3 cells: role of COX-2. Lin, S.Y., et al. 2002
