Leafy Greens Cut Lung-Cancer Risk by 50%

But pills don't deliver same protection

Spanish researchers report that a daily serving of green leafy vegetables, rich in flavonoids and vitamins A and C, may cut your risk of lung cancer in half. But don't think you can just pop a pill and get the same protective benefit: In a second new study, University of Washington scientists found that people taking vitamin supplements were just as likely to develop lung cancer as those not taking vitamins. In fact, in smokers, certain vitamins actually increased the risk of developing the disease.

In the first study, researchers at the University of Santiago de Compostela analyzed the diets of 617 individuals, including 295 lung-cancer patients and 322 healthy controls. Olga Dosil-Diaz, MD, PhD, and colleagues found that people who consumed at least one portion of green leafy vegetables a day had a 50% reduction in risk of developing lung cancer, compared to those who ate fewer than five portions per week.

While green leafy vegetables such as spinach were king, other vegetables — such as potatoes, cabbage, turnip tops, lettuce, tomatoes and green beans — also offered some protective benefit. Fruit, however, showed no protective benefit against lung cancer, regardless of the level of consumption.

The protective effect of the vegetables possibly was due to their antioxidant content, the researchers wrote. Vegetables are known to be rich sources of the vitamins A and C, as well as flavonoids, widely studied and touted for their association with risk reduction for certain cancers.

But while some — for reasons of taste or convenience — might prefer to get their nutrients by popping a vitamin pill instead, researchers at the University of Washington found that option ineffective against lung-cancer risk. Their four-year study tracked the supplement use — specifically multivitamins and C, E and folate — of nearly 78,000 people in Washington state, ages 50 to 76. During that time, 521 individuals developed lung cancer. The researchers did hot look at beta-carotene, which has been previously been shown to raise the risk of developing lung cancer among smokers.

Lead author Christopher G. Slatore, MD, wrote that these vitamins in pill form did not reduce lung cancer risk. Indeed, taking vitamin E supplements at a dose of 400 milligrams daily for 10 years was associated with a 28% increased risk of one type of lung cancer among current smokers.

The researchers said that while vitamin E is considered an antioxidant, it might function as a pro-oxidant, as well. "For folks — especially smokers — I would definitely recommend that they not take vitamin E (in supplement form) unless they have a very strong reason to take it," Dr. Slatore cautioned.

He added, "The best way to lower lung cancer risk continues to be to quit smoking."

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