Evidence supports the viewpoint that smoking increases free radicals, including reactive oxygen and reactive nitrogen species. Free radicals are harmful because they react with cells and tissues and lead to inflammation. Chronic inflammation can lead to ill health because it is believed to be involved in the development of diseases such as cancer and cardiovascular disease. Antioxidants can protect from cancer and cardiovascular disease because they decrease the propagation of free radicals and protect tissues from inflammation. Because of the increased production of free radicals associated with smoking, it might be expected that smokers have an increase dietary requirement for antioxidant nutrients. Indeed, studies have suggested that smoking increases the dietary requirement of vitamin C. Because vitamin C is able to interact with vitamin E in the plasma membrane, it might be expected that smokers also have depleted levels of vitamin E and could benefit from increased intakes.
Therefore if smoking increases free radicals, plasma antioxidant status might reflect this. To investigate the effects of smoking on the disappearance of plasma vitamin E in healthy subjects, researchers1 administered 10 smoking and 10 non-smoking individuals deuterium-labelled α-tocopheryl acetate (vitamin E) for 6 days. The researchers then measured the plasma α-tocopherol, ascorbic acid (vitamin C) and F2α-isoprostane levels (an oxidative stress marker) in blood samples and α-carboxy-ethyl-hydroxy-chroman (α-CEHC) (a breakdown product of vitamin E) in urine on day 6 to day 17. The results showed that smokers had increased levels of the oxidative stress markers F2α-isoprostanes (~40 % higher than controls), suggesting smoking increases free radicals. The smoking group also had increased fractional disappearance of α-tocopherol compared with controls (0.215 versus 0.191, respectively). The fractional disappearance of α-tocopherol correlated with the plasma levels of ascorbic acid in smokers, but not non-smokers.
This study shows that smoker have a faster disappearance of α-tocopherol from plasma compared to non-smokers, and supports other studies that have reported that smoking increases free radicals. As free radicals are produced antioxidants are depleted at a faster rate from tissues than would occur without the stress of smoking. The correlation between plasma vitamin C and α-tocopherol in smokers suggests that the α-tocopherol is depleted as it quenches free radicals and that vitamin C is then depleted as it both replenishes the α-tocopherol and also quenches other free radicals. Interestingly, by day 17 the smoking group had significantly lower levels of α-tocopherol, and increases in the urinary tocopherol metabolite α-CEHC. This may indicate that turnover of α-tocopherol had increased in smokers in response to the supplements. Therefore smoking increases free radicals, which may be one of the causes of the inflammation that leads to the development of smoking related disease.
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