Ascorbate, Smoking, And Supplementation

Nutrition Research Newsletter, March, 2000

Everyone knows that smoking is a health risk. It is associated with increased risk of cancer and CVD, it damages cellular functions because of the toxic chemicals and other oxidizing radicals, and it is addicting. Research has found that smokers often have low antioxidant levels and increased oxidative stress and damage from the high oxidant content of smoke. Therefore, it has been suggested that smokers would benefit from an increased intake of antioxidants.

Since smokers are known to have poorer diets than nonsmokers, it is difficult to distinguish between the effects of diet and smoking on serum antioxidant concentrations. A recent article in the American Journal of Clinical Nutrition examined the antioxidant status among smokers and nonsmokers by measuring total ascorbic acid (TAA) and a few lipid soluble antioxidants. The article also aimed to establish whether moderate supplementation can restore depleted antioxidants. In order to distinguish between the effects of poor diets among smokers, all subjects who were selected had equally low daily intakes of fruits and vegetables.

Fruit and vegetable intake was determined by a seven-question questionnaire. Low fruit and vegetable intake was considered less than or equal to three servings per day. Thirty-seven smokers and thirty-eight non-smokers were randomly assigned to either a placebo or a vitamin cocktail, containing 272 mg vitamin C, 31 mg all-rac-alpha-tocopheryl acetate and 400 [micro]g folic acid, for three months. The content of the supplement reflected a diet with [is greater than or equal to] 5 combined servings of fruit and vegetables per day. Blood samples were drawn to measure TAA, alpha-tocopherol, gamma-tocopherol, beta-carotene, and lycopene.

Total fruit and vegetable intake plus vitamins C and E, beta-carotene, and lycopene did not significantly differ between the two groups, which would have effectively isolated the effect of smoking on plasma antioxidant levels. Only vitamin C was significantly depleted by smoking. After the three-month supplementation period, ascorbic acid was significantly repleted in smokers. A 43% increase in TAA was observed in supplemented non-smokers, while a 194% increase was detected in supplemented smokers. Plasma alpha-tocopherol and the ratio of alpha- to gamma-tocopherol increased significantly in both supplemented groups.

The study shows that ascorbic acid is the only plasma antioxidant depleted by smoking and that these levels can be normalized by moderate supplementation. This data also comments on previous studies that reported that plasma vitamin E and carotenoids are lower in smokers. It is possible that this theory may have been caused by differences in dietary habits between smokers and non-smokers, and so cannot be substantiated.

Jens Lykkesfeldt, Stephan Christen, Lynn M Wallock, et al., Ascorbate Is Depleted by Smoking and Repleted by Moderate Supplementation: A Study in Male Smokers and Nonsmokers with Matched Dietary Antioxidant Intakes, Am J Clin Nutr 71: 530-536 (February 2000) [Correspondence: B. N. Ames, University of California, Dept. of Molecular and Cell Biology, 401 Barker Hall, Berkeley, CA. E-mail: bnames@uclink4.berkeley.edu.]