These drugs are the most powerful medications for reducing stomach acid levels; in fact, they almost completely shut down the stomach's ability to produce acid. (Their science fiction–sounding name comes from the last stage of the acid-secreting process, called the "proton pump.") Proton pump inhibitors are used for ulcers as well as for the treatment of moderate to severe esophageal reflux, commonly known as heartburn.

Drugs in this family include lansoprazole (Prevacid), omeprazole (Prilosec), and others.

St. John's Wort

The herb St. John's wort is known to interact with numerous drugs. There are two potential harmful interactions between St. John's wort and proton pump inhibitors.

One study found that use of St. John's wort greatly decreases levels of omeprazole in the body. 13 This would be expected to lead to markedly reduced efficacy.

The other potential risk is more theoretical. When taken to excess, the herb St. John's wort can cause an increased risk of sunburn. Some evidence hints that proton pump inhibitors might increase this risk. 12

Vitamin B 12

Vitamin B 12 deficiency is a concern with the use of all drugs that reduce stomach acidity.

In food, vitamin B 12 is always accompanied by proteins, and it must be separated from them before it can begin to be absorbed. Following separation, B 12 is then attached to a substance called intrinsic factor, which allows B 12 to be absorbed in the intestines.

Stomach acid plays a role in this separation. If you don't have enough stomach acid, the process of freeing vitamin B 12 from protein so that it can be bound to intrinsic factor may be impaired. 1,2

Studies suggest that treatment with proton pump inhibitors might significantly reduce the absorption of vitamin B 12 . 3,4,5

Interestingly, there is some evidence that cranberry juice might increase B 12 absorption in individuals taking proton pump inhibitors, 6 possibly because the juice is somewhat acidic.


Research on related medications suggests that proton pump inhibitors may slightly reduce the body's absorption of folate. 7 The decrease in folate absorption should be quite small, but since folate deficiency is quite common and potentially harmful, taking extra folate might make sense as insurance.

By reducing stomach acid levels, proton pump inhibitors might interfere with the absorption of iron , zinc , and perhaps other minerals. 8-11 Taking mineral supplements to meet the US Dietary Reference Intake (formerly known as the Recommended Dietary Allowance) levels for these nutrients should help.

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