Jack Campin wrote:

Trotter can't have been any sort of expert. Just look it up. A normal meal portion of sauerkraut contains far more vitamin C than the RDA. It's one of the best sources available without access to modern technology.

Someone who was the most knowledgeable person at a given time might turn out to not know so much in the long run. :-) Trotter had experience with scurvy (you can see his Wikipedia entry: https://en.wikipedia.org/wiki/Thomas_Trotter_(physician). It's his conclusions that were wrong.

Some of them. He was right about most of the portable soups; they didn't have much vegetable in them.

You're right that sauerkraut was high in vitamin C -- when fresh. But vitamin C is not a very stable chemical; it decays when exposed to heat or light. On a voyage to the tropics, it would lose some of its antiscorbutic properties. So would lemon juice. On a voyage like the Franklin Expedition, heat would matter less, since the ships were chilly -- but if they kept the lemon juice close to the stoves, the lemon juice probably would have been pretty weak by the third year. Which would fit with what we know about the expedition. Despite all the talk about lead, the best bet -- the one that best fits the available evidence -- is still scurvy.