Scurvy on a diet devoid or nearly devoid of vitamin C, had blood levels of vitamin C too low to be accurately measured when they developed signs of scurvy, and in the Iowa study, at this time were estimated (by labeled vitamin C dilution) to have a body pool of less than 300 mg, with daily turnover of only 2.5 mg/day. The vast majority of animals and plants are able to synthesize vitamin C, through a sequence of enzyme-driven steps, which convert monosaccharides to vitamin C. However, some mammals have lost the ability to synthesize vitamin C, notably simians and tarsiers.
Scurvy with many dying as a result. During the Age of Exploration (between 1500 and 1800), it has been estimated that scurvy killed at least two million sailors. Jonathan Lamb wrote: "In 1499, Vasco da Gama lost 116 of his crew of 170; In 1520, Magellan lost 208 out of 230;...all mainly to scurvy." In 1579, the Spanish friar and physician Agustin Farfán published a book in which he recommended oranges and lemons for scurvy, a remedy that was already known in the Spanish Navy. In 1593, Admiral Sir Richard Hawkins advocated drinking orange and lemon juice as a means of