Which dietary change should patients avoid while taking lithium therapy?

• A. Increased caffeine intake
• B. Moderate salt intake
• C. Restriction of dietary salt intake
• D. Vitamin C rich foods

Answer: (C)

Lithium therapy is tightly linked to how the kidneys handle sodium. Lithium is reabsorbed in the proximal tubule in a similar way to sodium, so anything that changes sodium balance directly affects lithium levels in the blood. If you restrict dietary salt, the body tries to conserve sodium by reabsorbing more filtrate, and lithium is reabsorbed as well, raising serum lithium and the risk of toxicity. Keeping a consistent, moderate sodium intake helps keep lithium levels stable.

In contrast, higher salt intake can increase lithium excretion and lower levels, and neither significantly high caffeine nor vitamin C-rich foods have a major, direct impact on lithium levels that would necessitate avoidance. Moderate salt intake is appropriate; the key is to avoid dietary salt restriction.