Which nutrient is poorly absorbed in achlorhydria?

In cases of achlorhydria, which is the absence of hydrochloric acid in gastric secretions, the absorption of several nutrients can be affected, particularly vitamin B12. The absorption of vitamin B12 in the intestines relies heavily on several factors, including the presence of intrinsic factor, which is produced by parietal cells in the stomach and is essential for the efficient uptake of vitamin B12 in the ileum.

Hydrochloric acid plays a critical role in the digestive process by enabling the release of vitamin B12 from food proteins. Without sufficient stomach acid, vitamin B12 remains bound to its protein sources and cannot be adequately released, leading to poor absorption. This deficiency can eventually result in vitamin B12 deficiency anemia, as well as neurological complications, since vitamin B12 is vital for the production of myelin and red blood cells.

While iron absorption is also affected by gastric pH, particularly in its ferrous form, and calcium absorption can be impaired due to the need for an acidic environment to solubilize calcium salts, vitamin B12 is specifically dependent on stomach acid for its release from food, making it distinctly poorly absorbed in cases of achlorhydria.