WASHINGTON (Reuters) - Vitamin C may help prevent the damage caused by second-hand tobacco smoke, offering a way for people to protect themselves from smokers in their lives, U.S. researchers said on Tuesday.

A small study of 67 nonsmokers exposed to environmental smoke showed those who took 500 mg of vitamin C daily had lower levels of a compound linked to the damage done by tobacco smoke.

"They show that vitamin C may help protect nonsmokers from the oxidative damage caused by second-hand tobacco smoke," Dietrich, a nutritional epidemiologist, said in a statement.

Writing in Tuesday's issue of the journal Nutrition and Cancer, Dietrich and other researchers tested for levels of F2-isoprostanes, which are generated through a form of oxidative stress called lipid peroxidation.

After two months, blood levels of F2-isoprostanes dropped by 11.4 percent for the vitamin C group compared with those taking the dummy capsule, and 12 percent for the C plus E plus ALA group.

"The message of the study is clearly not that taking vitamin C makes smoking or exposing others to smoke OK," she said. "But, if you are in a situation where you cannot escape frequent exposure to second-hand smoke, it may be worthwhile to take vitamin C supplements as a precautionary measure. And, as always, eat a diet rich in fruits and vegetables."

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I looked up F2-isoprostanes and saw nothing that makes it exclusive to smoking/SHS. So why didn't they have a group of nonsmokers not exposed to SHS and see what kind of drop they would have. From what I can tell this study says nothing more than anybody taking Vitamin C might benefit from it.