Which supplement is commonly used to treat upset stomach and diarrhea and may cause darkened tongue or stool in some people?

• A. Bismuth subsalicylate products
• B. Probiotics
• C. Loperamide
• D. Activated charcoal

Answer: (A)

Bismuth subsalicylate products are commonly used to soothe upset stomach and reduce diarrhea by both calming the stomach lining and helping decrease intestinal secretions. A distinctive side effect of these products is a darkening of the tongue or stools, which occurs when bismuth combines with trace sulfur to form bismuth sulfide. This discoloration is characteristic and widely reported with this specific treatment, making it a recognizable clue in the context of stomach upset relief.

Other options don’t fit this combination of therapeutic use and this specific side effect. Probiotics can help support gut health and may assist with certain types of diarrhea, but they don’t typically cause dark tongue or stool. Loperamide helps slow bowel movements to reduce diarrhea but isn’t associated with color changes in the tongue or stool. Activated charcoal can darken stool, but it isn’t a standard treatment for common upset stomach and diarrhea, and its use is more limited to certain poisoning scenarios or specific GI symptoms.

So the product that both treats upset stomach and diarrhea and can cause darkened tongue or stool aligns with the description.