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The Effect of Smoking on Vitamin C Requirements

1 The Effect of Smoking on Vitamin C Requirements Thereisev-idence that smokers have ahigher requirement for vitamin C them nonsmokers. A number of studies have shown lower plasma and leukocyte concentradons of vitamin C in smokers, but many also report lower intake of the vitamin by smokers. The rate of catabolism of ascorbate is up to 40% greater in smokers than nonsmokers (Kallner et al., 1981), emd therefore their vitamin C requirement may be eilmost twice that of nonsmokers. [Pg.380]

Regardless of whether or not high intakes of ascorbate have any beneficial effects, large numbers of people habitually take between 1 to 5 g per day of vitamin C supplements, and some take considerably more. The U.S. /Canadian tolerable upper level of intake is 2 g per day (Institute of Medicine, 2000). [Pg.380]

There is little evidence of rmy significemt toxicity from these high intakes, tdthough there are a number of potential problems (Rivers, 1987 Johnston, 1999). Because ascorbate is Irugely absorbed by active transport, absorption is saturable, and a decreasing proportion of high doses is absorbed. Similarly, once the plasma concentration has reached the renal threshold, the vitamin is excreted quantitatively with increasing intake (Section 13.2.1). [Pg.380]

Unabsorbed ascorbate in the intestined lumen is a substrate for bacterial fermentation, which may explttin the diarrhea and intestinal discomfort reported in some studies with high doses of the vitamin. [Pg.380]


See other pages where The Effect of Smoking on Vitamin C Requirements is mentioned: [Pg.435]    [Pg.311]    [Pg.178]   


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