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Green Tea, Broccoli, Flavonoids Protect Lungs of Smokers


If you want to protect your lungs and you smoke, quit. You might also want to include green tea, broccoli, and flavonoid-rich vegetables in your diet. That’s the word from three separate studies on the impact of various nutrients on the lungs of smokers.

The impact of burning tobacco on the lungs of smokers has been well studied and the link between smoking and lung cancer and other lung diseases such as emphysema is clear. Tobacco smoke contains more than 4,000 compounds, of which about 60 are known carcinogens. Smoking is also associated with a high level of oxidative stress and free radical damage, which depletes the body of antioxidants.

Results of several studies indicate that various natural substances have the ability to protect the lungs of smokers. In a recent study from Hong Kong, investigators found that daily consumption of green tea extract may slow the damage that cigarette smoke causes to the lungs. The benefit has been credited to an antioxidant and polyphenol called epigallocatechin gallate (EGCG), of which green tea is a rich source.

The Hong Kong researchers studied four groups of rats: those exposed to normal air, air with 4 percent cigarette smoke, normal air and fed green tea, and cigarette smoke and fed green tea. After 56 days, the rats exposed to cigarette smoke only had enlarged airspaces of the lungs and an elevated number of goblet cells, both signs of lung damage. These effects were not seen when the rats were simultaneously fed green tea. The rats exposed to cigarette smoke also had increased levels of 8-isoprostane, markers of oxidative stress in humans, but the rats fed green tea did not.

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In a study published in Cancer Prevention Research in December 2008 reported that a compound found in broccoli may help protect against lung cancer in people who smoke. The compound, indole-3-carbinol (I3C), is also found in other cruciferous vegetables, such as cauliflower, kale, bok choy, and brussel sprouts.

To arrive at their conclusion, the researchers used mice exposed to carcinogens found in tobacco smoke. The animals were fed different doses of indole-3-carbinol, and those that consumed the greatest amount of I3C had 88 percent fewer tumors than control mice. The scientists reported that indole-3-carbinol appeared to inhibit proliferation of cancer cells and enhance cell death.

In yet another study, this one conducted at the University of California, Los Angeles, looked at the impact of certain antioxidant flavonoids on the risk of lung cancer among smokers. Flavonoids are a type of antioxidants found in tea, red wine, fruits and vegetables. The researchers studied 558 patients who had lung cancer and 837 healthy individuals and evaluated their food intake. After adjusting for age, sex, smoking status, and race, the investigators found that certain flavonoids were associated with a decreased risk of lung cancer.

For example, 10 mg daily increase in the flavonoid epicatechin was associated with a 36 percent reduced risk of lung cancer, a 4 mg increase in catechin intake reduce lung cancer risk by 51 percent, and a 9 mg increase in quercetin intake reduced the risk by 35 percent. However, there was no association between intake of flavonoids and lung cancer risk among people who did not smoke.

The best way for smokers to protect their lungs is to quit smoking, but the addition of certain foods and nutrients, including green tea, broccoli and related vegetables, and foods rich in flavonoids may offer some protection as well. More research is needed to better identify the benefits of flavonoids and other antioxidants in the role of protecting the lungs of smokers.

Chan KH et al. Respiratory Medicine 2009 Nov; 103(11): 1746-54
Cui Y et al. Cancer 2008 May 15; 112(10): 2241-48
Kassie F et al. Cancer Prevention Research 2008 Dec; 1:568-76



This is very interesting. I am wondering if things like green tea and broccoli can help those who are trying to quit smoking to speed up the process: especially make it easier to fight the addiction after quitting.