A disease known long before its cause
Scurvy was recognised as a distinct affliction long before anyone understood its cause, with descriptions reaching back to ancient Egypt and Hippocrates, and it became a mass killer once long sea voyages during the Age of Exploration removed sailors from any source of fresh food for months at a time. Researchers estimate the disease killed at least two million sailors across this period; Vasco da Gama lost 116 of his 170-man crew to it in 1499, and Magellan lost 208 of 230. The claim eventually established was narrow and specific: that scurvy is caused by a dietary deficiency of a single compound, later named vitamin C, and that restoring even a small daily amount of it both prevents and, if caught in time, completely reverses the disease.
Lind’s trial and the decades of delay
James Lind, a Royal Navy surgeon, ran what is described as one of the first controlled clinical trials in medical history in 1747, giving groups of scurvy-afflicted sailors different proposed remedies, including cider, vinegar, seawater and citrus fruit, while holding their other conditions the same. His conclusion, that oranges and lemons were by far the most effective treatment, was clear-cut, but it occupied only a small portion of a much longer published work and made little immediate impact on naval practice. It took until 1795, after a four-month voyage of HMS Suffolk completed without a single case of scurvy, for the Admiralty to agree that lemon juice and sugar should be issued as a daily ration across the fleet, with the practice fully operational by 1800, nearly fifty years after Lind’s trial.
Isolating the compound
Understanding why citrus worked took longer still and required identifying an animal model, since most laboratory species can synthesise their own vitamin C and do not develop scurvy on a deficient diet. In 1907, Norwegian physicians Axel Holst and Theodor Frølich found that guinea pigs, unusually, could be made to develop scurvy, giving researchers a way to test candidate substances directly rather than relying only on human trials. Building on this, the Hungarian biochemist Albert Szent-Györgyi isolated a compound he called hexuronic acid from adrenal glands in 1927. At that point he suspected, but had not proven, that this was the substance responsible for preventing scurvy; the isolation itself was a chemical achievement that did not yet answer the biological question it was isolated to address.
King’s confirmation
The confirmation came from a different researcher working separately. Charles Glen King, at the University of Pittsburgh, proved in 1932 that Szent-Györgyi’s hexuronic acid was in fact the antiscorbutic compound, after which it was renamed ascorbic acid. Szent-Györgyi received the 1937 Nobel Prize in Physiology or Medicine for work connected to this discovery, but the sequence itself illustrates a real distinction that is easy to collapse into a single triumphant moment: isolating a chemical compound from a biological source is a separate achievement from proving that compound is responsible for a specific biological effect, and in this case the two steps were five years and two different laboratories apart.
What ten milligrams a day actually does
Once the mechanism was understood, later trials, including studies conducted during the Second World War and again in the 1960s, established the practical numbers with more precision than Lind’s era could manage: symptoms of scurvy develop after roughly four weeks on a vitamin C-free diet, and supplementing with as little as 10 milligrams a day is enough to reverse those symptoms completely, usually within about two weeks of treatment beginning. The underlying biochemical reason is that vitamin C acts as a required cofactor for the enzymes that stabilise collagen, the connective tissue protein responsible for skin, blood vessel and gum integrity, and without it collagen cannot cross-link properly, producing the bruising, bleeding gums and tissue breakdown characteristic of the disease.
Where the claims outran the evidence
This is worth reading in full because the vitamin C story is really two stories with very different endings, and conflating them is where public understanding usually goes wrong. The first, the discovery that a specific compound prevents and cures scurvy at a small daily dose, is thoroughly established and holds up completely. The second, popularised chiefly through Linus Pauling’s advocacy from 1970 onward for much larger doses against the common cold and other illnesses, has not fared nearly as well: trials using more than 200 milligrams a day, including ones testing over 1,000 milligrams, found no meaningful preventive effect on catching a cold, only a modest reduction in how long or severe an illness already underway turned out to be. Readers who know the scurvy story tend to assume the megadose claims share its evidence; they do not.