By and far, smoking is the biggest risk factor for lung cancer. In fact, up to 90 percent of the lung cancer cases in the U.S. can be attributed to smoking.1
But what about the remaining cases of lung cancer—the ones that affect people who’ve never smoked? What factors influence that cancer development? Furthermore, not all smokers develop lung cancer. About 15 percent are spared this dreaded diagnosis. What is it that protects this extremely high-risk group?
According to recent research, the intake of flavonoids may be the answer.2
What Are Flavonoids?
By now, you’ve probably heard of antioxidants—nutrients that protect the body from molecules called free radicals, which alter the DNA of cells and permanently damage them, potentially leading to disease. Well, flavonoids are a huge group of antioxidant compounds, found primarily in fruits, vegetables and some beverages like tea and wine.
Flavonoids are further broken down into six main subclasses:
- Flavonols—The most well-known flavonol is quercetin, which is abundant in red wine, but also in berries, teas, broccoli and apples.
- Flavones—found primarily in the skin of citrus fruits.
- Flavanones—found in citrus fruits.
- Flavanols—Catechins are the most common flavanol. Tea and cocoa are excellent sources of catechins. Proanthocyanidins, another flavanol, are abundant in berries, red grapes and red wine.
- Anthocyanidins—found in blue and red produce, like berries and red grapes, as well as red wine.
- Isoflavones—most abundant in soy and other legumes.
As a whole, research has shown that flavonoids can be powerful disease fighters and preventers, thanks to their anti-inflammatory, anti-mutagenic and anti-proliferative properties.3 Some animal studies even indicate that dietary flavonoids exist in lung tissue, possibly playing a role in cancer prevention.4
Taking this into account, researchers in Montreal followed 2,486 male and female participants (1,061 lung cancer patients and 1,425 controls) between the ages of 35 and 75.
Researchers conducted interviews with all the participants to assess lifestyle behaviors (smoking, drinking, diet, etc.) and occupational history. Using a food frequency questionnaire, they also assessed dietary habits of all the participants—two years prior to lung cancer diagnosis in the cases, and two years prior to being interviewed for the controls.
After analyzing the data they collected, researchers found that total flavonoid intake was not associated with lung cancer risk. The results were similar, regardless of sex or smoking level. However, they did link low flavonoid intake from foods, but not from beverages, with a higher risk of lung cancer overall—specifically squamous cell carcinoma.
While the researchers did not find statistically significant evidence of positive flavonoid effect based on how much someone smoked, there were reduced risks in moderate to heavy smokers were seen in those who fell into the middle quartiles for total flavonoids, flavanols and flavonols, as compared to light or nonsmokers.
Overall, the researchers concluded that, although smoking is the biggest risk factor for lung cancer, adding flavonoid-rich foods to your diet can offer an avenue for prevention and protection that otherwise would not be there.
Adding flavonoids to your diet is pretty easy. Simply increase your intake of all sorts of berries and other fruits, vegetables, legumes and dark chocolate (the highest percentage of cocoa with the fewest grams of sugar that you can find).
And even though the study did not find that flavonoid-rich beverages provided lung cancer protection, drinking tea (green in particular) and red wine offers many other health benefits, including significantly reduced risk of cardiovascular disease.5-6 So it definitely doesn’t hurt to drink more green tea and enjoy a small glass of red wine a few nights a week.
If you prefer to take flavonoids in supplement form, there are several options available, including quercetin, citrus bioflavonoids and green tea extract.
- Centers for Disease Control and Prevention. www.cdc.gov/cancer/lung/basic_info/risk_factors.htm#2.
- Christenson KY, et al. Nutr Cancer. 2012 Oct;64(7):964-74.
- Ross JA and Kasum CM. Annu Rev Nutr. 2002;22:19-34.
- de Boer VC, et al. J Nutr. 2005 Jul;135(7):1718-25.
- Peterson JJ, et al. Nutr Rev. 2012 Sep;70(9):491-508.
- McCullough ML, et al. Am J Clin Nutr. 2012 Feb;95(2):454-64.