Could any punishment be worse than being forced to eat stones? Jeremiah used this graphic image to show how severely the Lord was punishing the nation of Judah for her sin and idolatry.
The prophet may have drawn this image from the impurities such as sand and gravel that often got mixed in with the bread of Bible times. The methods used to harvest grain (Ruth 3:2) and grind it into flour (Proverbs 27:22) were primitive and unsanitary by modern standards.
LAMENTATIONS 3:16 – He [God] hath also broken my teeth with gravel stones.