In order to work properly, our cells need certain chemicals that they can’t manufacture on their own. These substances, called vitamins, are found in foods, and do everything from improving our vision to keeping our gums healthy (which is why not getting enough of a certain vitamin can make you sick). The body needs at least 13 vitamins, ranging from A to K, though it’s possible there are a few varieties that haven’t been discovered yet.
To give an example of why vitamins are important, sailors used to go to sea for months at a time without fresh produce, and therefore were prone to develop scurvy – a painful disease marked by rotten gums, difficulty breathing, and disorientation. Scurvy is a condition caused by a lack of vitamin C, which is found in fresh food and vegetables. The problem was solved by a doctor’s in the early 19th century, when he discovered scurvy could be prevented by adding lime juice to sailors’ diets. This is how sailors got the nickname ‘limeys’.