Q. Can vitamin C supplements protect me from getting lung cancer from secondhand smoke?

A. The surgeon general recently warned that any amount of secondhand smoke exposure is dangerous. Although smoking has been banned in restaurants and many workplaces in Hawai'i, those who live with smokers may not be able to avoid exposure to it.

The levels of vitamins C and E are reduced in smokers. Vitamin E is one of the first lines of defense against toxins generated by cigarette smoke. Vitamin C supplements reduce vitamin E losses in smokers.

Vitamin C supplements also decrease oxidative damage to the cells of smokers. Oxidation in the body is similar to the process of rust damaging metal. Oxygen mixes with certain chemicals in the body, damaging cells. This increases cancer and heart disease risk. Vitamins C and E are called anti-oxidants because they help prevent oxidation.

Nonsmokers exposed to secondhand smoke also have low vitamin C levels. Several years ago, University of California researchers wanted to find out if vitamin C could reduce oxidative damage in folks exposed to secondhand smoke as it does in smokers.

The study divided 67 nonsmokers who were regularly exposed to secondhand smoke into three groups. One group was given 500 milligrams of vitamin C daily. The second group was given a mixture of vitamin C, vitamin E and the antioxidant alpha-lipoic acid. The third group took placebo capsules.

Levels of F2-isoprostanes were measured. These substances cause cell damage and form artery-blocking plaque. After two months, blood levels of F2-isoprostanes dropped by 11 percent for the vitamin C group and 12 percent in the group taking the mixture.

Vitamin C was beneficial even without the addition of vitamin E and alpha-lipoic acid.

This study was done for too short of a time to predict whether the vitamin takers are less likely to develop lung cancer or heart disease in the future.

In a later study, vitamin C supplements reduced C-reactive protein in smokers and those exposed to secondhand smoke. High levels of this protein can increase heart disease risk.

Taking vitamin C doesn't make smoking or exposing others to smoke healthy. However, if you can't escape frequent exposure to second-hand smoke, it may be worthwhile to take vitamin C supplements. You should also eat lots of vitamin C-rich foods such as papayas, mangos, strawberries, bell peppers and broccoli.

Amy Tousman is a registered dietitian and certified diabetes educator. Hawai'i experts in traditional medicine, naturopathic medicine and diet take turns writing the Prescriptions column. Send your questions to: Prescriptions, Island Life, The Advertiser, P.O. Box 3110, Honolulu, HI 96802; fax 535-8170; e-mail islandlife@honoluluadvertiser.com. This column is not intended to provide medical advice.