While vitamins can't compensate for all the harmful effects of smoking, a study finds that supplementation with vitamin C can replenish the body's stores of one nutrient that is specifically depleted by smoking.
Supplementation with vitamin C produced significant benefits for smokers. Smokers are more likely than nonsmokers to benefit from vitamin C supplementation because they are more likely to be deficient in ascorbic acid. Even modest supplementation of vitamin C, 272 mg daily, had a large effect on smokers.
As a group, smokers consume more fat, fewer fruits and vegetables and only three-quarters of the recommended daily allowance for vitamin C. In addition to their poorer eating habits compared with nonsmokers, smokers have depleted levels of antioxidants in their bodies as a result of breathing in cigarette smoke.
The study was a joint effort between researchers at the University of California, Berkeley (www.mcb.berkeley.edu) and the Western Human Nutrition Research Center in Davis, Calif., part of the U.S. Department of Agriculture (www.usda.gov). Results are published in the February 1 issue of The American Journal of Clinical Nutrition (www.ajcn.org).
Volunteers were healthy male smokers, ages 20 to 50, from the San Francisco Bay area, specifically chosen because they had poor diets, typically consuming fewer than three servings of fruits and vegetables a day.
Baseline blood samples were taken, and half of the group were provided with a vitamin supplement for a 90-day period. The other half took a placebo.
This study matched smokers and nonsmokers in their dietary habits. The depletion of ascorbic acid was not due to dietary differences between the groups studied.
The authors measured levels of a number of different antioxidants, including vitamin C, and several different forms of vitamin E. They concluded that vitamin C was the only antioxidant that was significantly affected by smoking.
Lynn M. Wallock, one of the study leaders and an assistant research scientist at the Children's Hospital Research Institute in Oakland, Calif., said the team was surprised by the vitamin C finding: "The other [antioxidants] don't appear to be depleted," she said.
According to the authors, "After the three-month supplementation period, ascorbic acid was efficiently repleted in smokers." In fact, smokers showed a substantial threefold increase in vitamin C levels after supplementation compared with nonsmokers or subjects in the placebo group. They added: "Smokers in particular seem to respond to this supplementation."
Previous studies have been unable to distinguish between effects of smoking and diet on plasma levels of antioxidants. One of the researchers' primary objectives, therefore, was to effectively differentiate between the two.
"The subjects were selected for an equally low daily intake of fruit and vegetables," the authors wrote. "A consequence of selecting for similar dietary habits was that vitamin C and E intakes from the normal diet did not differ significantly between smokers and nonsmokers. This enables the isolation of the effect of smoking itself."
"Because we were able to control for diet, we've clarified the picture," said Wallock.
She urged smokers to improve their diet by consuming more vitamin C (in the form of increased fruit and green, leafy vegetable intake) or by supplementing their diet with vitamin C.
