Did they know that it was from vitamin c deficiency? Could they have extracted and carried vitamin c with them to avoid the problem?
They did not know that it was caused by lack of vitamin C specifically, but at a point they did know that drinking like juice would prevent it, hence why sailors were sent to sea with limes and became known as “limeys.”
Multivitamins would have prevented it, but they simply didn’t have the technology or knowledge to produce them.
> Did they know that it was from vitamin c deficiency?
You are looking at this backwards.
The substance commonly known today as Vitamin C was first discovered in the 1910s, and proven to prevent scurvy in the 1930s.
This is why it got the chemical name ascorbic acid, from the Latin scorbutum meaning scurvy. They basically named it “anti-scurvy stuff”.
The sailors of old didn’t know about Vitamin C. They knew scurvy, and over time learned that certain foods could prevent and cure it. On that basis, scientists then isolated some common ingredients of these foods, and found out which one was the actual cure for scurvy.
And by extension, they found out that the cause for scurvy must be a lack of that substance, which they called ascorbic acid or Vitamin C.