What was James Lind’s scurvy experiment?
In May 1747, aboard HMS Salisbury, the naval surgeon James Lind took twelve sailors with scurvy, kept them in the same conditions and gave six pairs six different remedies. Within six days the pair on oranges and lemons were recovering. It was a controlled comparison: similar patients, the same conditions, different treatments.
In the 1740s, the most dangerous thing on a long sea voyage wasn't the enemy. It was scurvy. Gums swelled and bled, old wounds reopened, and sailors grew too weak to stand. Commodore Anson's voyage round the world, which set out in 1740, lost most of its men to disease, much of it scurvy.
Everyone had a theory about the cause. Almost nobody tested one. In May 1747, a naval surgeon called James Lind was aboard HMS Salisbury. He took twelve sailors with scurvy, as alike as he could find. They slept in the same part of the ship and ate the same basic diet. Then he split them into six pairs and gave each pair a different remedy: cider; a few drops of dilute sulphuric acid, called elixir of vitriol; vinegar; sea water; two oranges and a lemon a day; or a medicinal paste.
Within six days, the pair on oranges and lemons were recovering, and one was fit for duty. The cider pair improved a little. The rest did not. What Lind did is called a controlled comparison: similar patients, the same conditions, different treatments. If the groups start alike and are treated alike apart from the remedy, a difference at the end points to the remedy.
It wasn't a perfect experiment. Two sailors per remedy is tiny: one unusual sailor could swing a result. And Lind chose who got what himself, so his own judgement could have crept in. Today we'd let chance decide, and use far more people. But the core idea was right, and it's the root of everything in this series. Don't ask whether people who happened to eat citrus did better. Give the remedies to similar people, and compare.
Here's the strange part. Lind didn't know why citrus worked. Nobody did: vitamin C wasn't identified until around 1930. Lind himself suggested preserving the juice by boiling it down, which we now know destroys much of the vitamin. The Royal Navy didn't make lemon juice a standard ration until 1795, nearly fifty years after the comparison.
Later in the 1800s it switched from Mediterranean lemons to West Indian limes, which carry far less vitamin C, and scurvy returned on long polar voyages. You can show that something works without knowing why. But without the why, it's easy to change the very thing that made it work.
For food and farming, that lesson keeps coming back. The variety, the soil, the storage, the processing: each can change what's in the food, even when the label stays the same. Throughout this series we'll keep asking two questions. Does it work? And what exactly is "it"?
Next: a philosopher who, a year later, wrote down what a cause actually is, and the century in which statistics tried to do without the idea.
Two sailors per remedy is tiny, so one unusual sailor could swing a result. And Lind chose who got what himself, so his own judgement could have crept in. Today we would let chance decide who gets which treatment, and use far more people. But the core idea, giving the remedies to similar people and comparing, was right.
Later in the 1800s the navy switched from Mediterranean lemons to West Indian limes, which carry far less vitamin C, and scurvy returned on long polar voyages. Nobody yet knew why citrus worked, so it was easy to change the very thing that made it work.
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