Sailing has always been a major industry and passion throughout the history of humanity, civilizations have been shaped and fallen because of their ability to open up shipping routes or discover new lands. Known as the Age of Sail, which is usually dated from around 1571 to 1862, it was a period during which international trade and naval warfare were primarily made up of sailing ships.
During the Golden Age of Sail where the sailing vessels reached their peak size and complexity, it is estimated that around 50% of sailors died from scurvy on any trip. Scurvy is a disease that happens due to a lack of vitamin C, early symptoms include simply being tired or suffering from sore arms or legs. But without treatment, the decrease in red blood cells start to cause major problems for any patient. As it worsens you will find poor wound healing, personality changes and then eventually death from infection.
It takes at least a month of no vitamin C in a diet to start seeing the symptoms, and this is why sailors during the Age of Sail were so at risk. During this time long cargo hauls or whaling trips would see a sailor being out at sea for months. It took until 1753 for the British Royal Navy to start routinely giving their sailors lemon juice to ensure no scurvy would be present.
But one group of interesting sailors never suffered from the disease at all. These were the Basque sailors, who were very successful in dominating the whale oil trade for some time. They were extremely skilled at hunting whales, and as a result, always had whale oil to trade. One of the ways they achieved this was incentivizing the sailors, they were one of the first sailors to have contracts that ensured payment. And the payment had to be made in some part in oil, this gave them further motivation to produce as much whale oil as possible.
The real interesting part of their contracts though, which was how they never caught scurvy, even though they probably did not know at the time: the contract stipulated Basque sailors had to receive at least 2 to 3 liters of sagardoa each day. Now sagardoa is a type of strong Basque cider, which as a result contained vitamin C, and prevented scurvy.