Proton-pump inhibitors (PPIs) and histamine-2 receptor antagonists (H2 blockers) are commonly prescribed for treating ulcers and gastroesophageal reflux disease (GERD). Lansoprazole, or Prevacid, is a PPI that ranked third in top pharmaceutical sales in the United States in 2004.12 Many studies indicate that these classes of drugs cause several nutrient deficiencies. Research indicates that treatment with both PPI and H2 blockers increases the risk of vitamin B12 deficiency significantly in elderly patients.13 Studies have shown that H2 blockers decrease protein-bound (as opposed to unbound) vitamin B12 absorption, owing to decreasing gastric acid and pepsin secretion and a resultant inability to cleave cobalamin. One small study showed a 53% decrease in protein-bound B12 absorption in individuals taking an H2 blocker.14 In addition, decreased protein-bound B12 absorption would not be detected on the standard Schilling test, as it measures unbound cobalamin only.15
Research also indicates that folic-acid absorption is decreased with supplementation of H2 blockers and other antacids.16 Studies have linked H2 blockers, which decrease gastric acid secretion, with decreased absorption of iron and zinc.17,18 One study showed a direct correlation between increasing dosage of cimetidine, an H2 blocker, and decreasing dietary non-heme iron absorption ranging from 28%-65%.19
Animal studies have demonstrated that cimetidine significantly decreases intestinal calcium transport.20 Cimetidine also alters vitamin D metabolism by altering the enzyme vitamin D 25-hydroxylase activity, suppressing the seasonal increase in the level of 25-hydroxyvitamin D. The levels of 25-hydroxyvitamin D rose significantly after withdrawal of the drug.21 A small study performed with the PPI omeprazole demonstrated that serum levels of beta-carotene were decreased with increased gastric pH.22 These findings raise the question of the long-term potential consequence for increased risk of osteoporosis, other vitamin D-linked disease states, such as various cancers and multiple sclerosis, and altered RNA and DNA production as a consequence of lowered B12 and folate.
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