Answer: Omeprazole (Prilosec), Nexium, and other proton pump inhibitor drugs can be affected by taking supplements, and can affect your ability to absorb certain vitamins and minerals. St. John's wort, for example, should not be taken with these drugs. These interactions are explained in the Proton Pump Inhibitorsarticle, which is part of the extensive Drug Interactions section of our website (where you can look up interaction for other drugs you may be taking).
Be sure to also read about magnesium depletion which can occur with these drugs in the Magnesium Supplements Review. And, if you take a calcium supplement, read in the Calcium Supplements Review how certain forms of calcium may be preferable if you are taking these drugs.