Flavonoids (or bioflavonoids), also known as Vitamin P and citrin, are a class of plant secondary metabolites which can protect the smokers’ health. Flavonoids have antioxidant activity. Flavonoids are becoming very popular because they have many health promoting effects. Some of the activities attributed to flavonoids include: anti-allergic, anti-cancer, antioxidant, anti-inflammatory and anti-viral. Flavonoids are a type of antioxidants found in tea, red wine, fruits and vegetables.

Scientists’ advice: “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 effects of burning tobacco on the lungs of smokers have been well investigated and the link between smoking and lung cancer and other lung diseases such as emphysema became clear. As it is known 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 harm, which exhaust the body of antioxidants. Not only one study but a lot of studies indicate that several natural substances have the power to safeguard the smokers’ lungs. For example in a previous research from Hong Kong, investigators found that daily use of green tea extract may slow the damage that cigarette smoke causes to the lungs, only because green tea is a rich source of an antioxidant and polyphenol called epigallocatechin gallate (EGCG).

These findings were found by the Hong Kong researchers who 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, they observed that the rats exposed to cigarette smoke only had expanded airspaces of the lungs and a raised number of goblet cells, both signs of lung damage. These effects were not seen when the rats were at the same time 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.

Researchers added also that they discovered that a compound found in broccoli may also help protect against lung cancer in people who smoke. To arrive at their result, 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 enhances cell death.

The researchers also 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.

Researchers concluded that 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.