Scurvy is a nasty disease. It causes collagen, the protein substance found in the fibers of connective tissue, bone, and cartilage, to form improperly, meaning wounds don't heal, gums bleed, and severe pain occurs.
If untreated, it leads to death.
But in 1747, James Lind, a Scottish naval surgeon, fed lemons and limes to sailors with scurvy, and soon the symptoms stopped. After a few years of stopping scurvy this way, Lind wrote a paper about it. The British Royal Navy was impressed and adopted the practice yet others kept searching for better treatments.