1929: Sir Frederick Hopkins
Hopkins (Cambridge University) won the 1929 Nobel Prize in Physiology or Medicine for the discovery of essential nutrients, now known as vitamins, which are needed in animal diets for growth and for health. Before his work, most researchers believed that diet-linked illnesses, such as the scurvy that sailors suffered from during long trips, were caused by a toxic substance in certain foods. But Hopkins suspected that such diseases were actually due to something missing in the diet.
He studied the diets of rats and found that they would grow well only if he added a daily supplement of milk to their diet. He suggested that this was because of an unidentified organic nutrient. Other scientists went on to identify and characterise the individual nutrients as vitamins.