It's not an unusual idea. Iodized salt has small amounts of iodine to prevent thyroid problems amd mental impairment. (Iodine deficieny is the most common cause worldwide of metal impairment.) Flour is fortified with iron, calcium, thiamin, and nicotinamide.

Fortifying food and water supplies helps reduce illness and disease.

(I'm not suggesting that Lithium is suitable for this).