Which of the following substances can irritate the digestive tract leading to ulcers?

The presence of NSAIDs (nonsteroidal anti-inflammatory drugs) and smoking as irritants in the digestive tract leading to ulcers is well-documented. NSAIDs, such as ibuprofen and aspirin, can inhibit the production of protective mucus in the stomach lining and disrupt the balance of gastric acids, resulting in an increased risk of ulcer formation. These drugs decrease the synthesis of substances like prostaglandins, which are important for maintaining the stomach's protective barriers.

Smoking further exacerbates this risk by impairing blood flow to the stomach lining and reducing the overall healing ability of the gastrointestinal tract. It also leads to increased gastric acid secretion, all of which can contribute to ulcer development.

In contrast, fiber and probiotics are generally beneficial for digestive health; they help maintain a balanced gut microbiome and promote intestinal regularity. Carbohydrates and proteins are essential nutrients that typically do not cause irritation. Vitamins and minerals, while crucial for overall health, do not have properties that would typically lead to ulcers. Therefore, NSAIDs and smoking are specifically identified as significant irritants in the context of ulcer formation in the digestive system.