What was the disease people contracted from being on ships for prolonged periods?

The disease often associated with long sea voyages, especially during the age of sail, is scurvy. Scurvy is caused by a severe deficiency of vitamin C (ascorbic acid) in the diet. This deficiency leads to symptoms such as anemia, debility, exhaustion, spontaneous bleeding, pain in the limbs and joints, swelling in various parts of the body, and sometimes ulceration of the gums and loss of teeth. Scurvy was common among sailors as their diets during long voyages lacked fresh fruits and vegetables. It could be deadly if not treated.

The importance of vitamin C relates to its role in the production of collagen, which is vital for the maintenance of healthy connective tissues. It also helps in the healing of wounds and the maintenance of bone health. The body does not store vitamin C, so regular intake is essential. In the past, fresh produce was not always available on long sea voyages, leading to the deficiency.

Scurvy was a significant issue during long voyages until the 18th century when the British Navy adopted the practice of providing lemon juice (and later lime juice) to their sailors, famously earning British sailors the nickname "limeys." This practice was based on physician James Lind's experiments, which showed that citrus fruits could prevent scurvy. Lind's discovery was one of the first examples of a clinical trial and marked a significant advancement in nutritional science and naval health. Today, scurvy is rare in most parts of the world where fresh fruits and vegetables are readily available.