The researchers observed that the medication alters the distribution of minerals in the body, with accumulation in the stomach and imbalances in the spleen and liver. In the blood, they observed an increase in calcium and a drop in iron, indicating a risk of osteoporosis and anemia. Important changes in immune system cells were also detected.
In the research, adult rats were divided into different groups: control and treated with omeprazole. The experiments lasted 10, 30 and 60 days, periods chosen to simulate different levels of prolonged use of the medicine in humans.
“The most worrying finding was the significant increase in calcium in the animals’ bloodstream, which may indicate an imbalance with the removal of the mineral from the bones and future risk of osteoporosis. However, longer studies are needed to confirm this hypothesis”, says Angerson Nogueira do Nascimento, professor at Unifesp who coordinated the study in partnership with Fernando Fonseca, from FMABC.
Medications such as omeprazole, pantoprazole and esomeprazole act by inhibiting the enzyme H+, K+, ATPase. Known as the proton pump, it is responsible for the final stage of hydrochloric acid production in the stomach. By reducing gastric acidity, these medications alleviate symptoms of ulcers, gastritis and reflux, but they also hinder the absorption of nutrients that depend on an acidic environment.
With more than 30 years on the market, omeprazole has become widely used, often on a prolonged basis and without medical supervision. “This is not about demonizing the medicine, which is effective for various gastric conditions. The problem is its trivialized use, including for mild symptoms such as heartburn, and for prolonged periods of months and even years. Its adverse effects should not be neglected”, warns Andréa Santana de Brito, a researcher at Unifesp. The study was the subject of his master’s research.
She highlights that the situation could worsen with the new Anvisa ordinance, which authorized, in November 2025, the sale of omeprazole 20 mg without a medical prescription. “This facility can encourage self-medication and continuous use, disregarding the recommendation to limit treatment to 14 days”, he warns.
