Which of the following nutrients may be decreased in absorption due to the use of antacids like Tums and Zantac?

The absorption of folic acid may be decreased by the use of antacids such as Tums and Zantac. Antacids primarily work by neutralizing stomach acid, which can significantly alter the pH level in the stomach and intestines. Folic acid, which is a water-soluble B vitamin, requires an acidic environment for optimal absorption. When the stomach's acidity is reduced by antacids, the solubility and, ultimately, the absorption of folic acid may be impaired.

In contrast, while the absorption of some vitamins and minerals can be affected by changes in gastric pH, the other nutrients listed typically have different absorption mechanisms or conditions. Vitamin C, being a water-soluble vitamin, does not show significant absorption issues related to stomach pH changes. Vitamin D is fat-soluble and primarily relies on the presence of dietary fat for absorption rather than stomach acidity. Calcium absorption can be influenced by stomach acidity, but the context of the question points specifically to folic acid's absorption challenges in an alkaline environment created by antacid use. Therefore, the decreased absorption of folic acid is particularly notable in the context of antacid consumption.