Proton Pump Inhibitors Reduce the Bioavailability of Dietary Vitamin C
Abstract & Commentary
By Malcolm Robinson MD, FACP, FACG, Emeritus Clinical Professor of Medicine, University of Oklahoma College of Medicine, Oklahoma City. Dr. Robinson serves as a consultant for TAP, Pfizer, Janssen, Eisai, J&J-Merck, and Procter & Gamble, is on the speaker’s bureau of Janssen, Eli Lilly, Solvay, TAP, and Aventis, and does research for Forest Labs, Wyeth-Ayerst, AstraZeneca, and Centocor.
Synopsis: Even a short course of omeprazole reduces plasma vitamin C levels in healthy volunteers, and this effect would be expected to be magnified in H. pylori-positive individuals who have low pre-treatment vitamin C levels.
Source: Henry EB, et al. Proton pump inhibitors reduce the bioavailability of dietary vitamin C. Aliment Pharmacol Ther. 2005;22:539-545.
Known to be an essential nutrient, vitamin c is actively secreted by healthy gastric mucosa and is present in the gastric lumen as ascorbic acid (its reduced form). With higher gastric pH values, far lower levels of ascorbic acid and vitamin C are present in the stomach (and vitamin C is known to be unstable at high pH values). Henry and colleagues have shown that patients with H. pylori infections treated with omeprazole for 2 months exhibit both lowered gastric juice and plasma vitamin C concentrations.1 The present study was designed to evaluate healthy subjects both with and without H. pylori infections. Dietary intake of vitamin C was carefully estimated, and all subjects had HPLC assessments of total plasma ascorbic acid and vitamin C levels before and after 4 weeks of omeprazole 40 mg daily. H. pylori-positive subjects had lower baseline dietary vitamin C intake (35.9 mg vs 130.9 mg for the H. pylori-negative subjects), and H. pylori-positive subjects also had lower baseline plasma vitamin C concentrations (16.3 µg/mL vs 25.6 µg/mL). After 4 weeks of omeprazole, both groups exhibited further decreases in mean plasma vitamin C levels (approximately 12%). Gastric pH studies confirmed the expected augmented pH elevation in the H. pylori-positive group (pH > 4 for 50.7% of the interval in H. pylori-negative subjects vs 92.3% for the H. pylori-positive subjects.
Commentary
Dr. McColl’s group hypothesized that the lower vitamin C dietary intake in the H. pylori-positive subjects was due to their lower socioeconomic status. Although it is possible that lowering of vitamin C plasma levels in normal individuals without H. pylori might have untoward clinical consequences, the risks in H. pylori-positive individuals would be expected to be substantially higher. Low vitamin C status is a known risk factor for gastric cancer, and it is certainly possible that vitamin C deficiency might synergize with H. pylori to augment gastric cancer risk in infected individuals. PPIs are among the most widely used medications, and they are generally accepted as extremely safe. However, a few studies now exist that suggest that the pharmacological effects of PPIs on acid secretion may not ultimately prove to be quite as benign as some have thought. Careful chronic prospective surveillance of PPI recipients should continue.
References
1. Mowat C, et al. Omeprazole and dietary nitrate independently affect levels of vitamin C and nitrite in gastric juice. Gastroenterology. 1999;116:813-822; Erratum in: Gastroenterology. 1999;116:1507.
Even a short course of omeprazole reduces plasma vitamin C levels in healthy volunteers, and this effect would be expected to be magnified in H. pylori-positive individuals who have low pre-treatment vitamin C levels.You have reached your article limit for the month. Subscribe now to access this article plus other member-only content.
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