From the blockade book:
Sailors in the Union navy were generally a healthy lot, healthier on the whole that their counterparts in the army. This was due in large part to the fact that the navy was able to draw on long-established experience in keeping men healthy at sea. Most of the hundreds of naval officers appointed during the war came from the merchant service and thus had a solid background in shipboard management. The same was not true of the army, which had no counterpart in the civilian world and called upon the leadership of newly commissioned officers drawn from every professional background imaginable. Both afloat and ashore, more men died of disease than from combat, but about one in twelve Union soldiers would die of illness during the war, compared to about one in fifty Union sailors. . . .
Scurvy remained an ongoing problem for the navy, particularly among the blockading squadrons. Scurvy is a nutritional disease caused by a lack of vitamin C, which is commonly found in fresh vegetables and fruit, particularly citrus. Scurvy causes a general debilitating weakness, anemia, skin hemorrhages and gum disease and can be fatal. Although mariners in nineteenth century did not know the exact mechanism of scurvy, they had a good empirical knowledge of both of its treatment and prevention. As a result, occasional cases of scurvy among the blockaders came about not through ignorance or carelessness but due to the extremely long and complex supply chain that made it difficult to keep the fleet stocked with fresh provisions. The problem was especially acute for those ships and men of the West Gulf Blockading Squadron, who stood at the end of a very long supply chain. Winfield Scott Schley, a naval officer who would later rise to fame during the Spanish-American War, recalled that during his time on the blockade off Mobile, scurvy “was only avoided by the occasional relief which came to them afterward from the steamers bringing supplies of fresh meats and vegetables in amounts about enough for two or three days. The diet for the rest of the month was composed mainly of salted meats, cheese, hard bread, bad butter, inferior coffee and positively bad tea. It is indeed a wonder that the efficiency of the personnel was maintained at all under such condition.” At one point in the summer of 1862, the problem of scurvy had become so serious that Farragut had to send three ships of his command to northern ports to recover. Scurvy in particular seems to have plagued ships whose distance from regular sources of supply was extreme. Over the next three years, there were regular reports of the disease from vessels off the Texas coast where, as Farragut noted, “the ships are in much need of [vegetables] to avoid scurvy.” The Union sailing vessel Midnight, for example, spent nine months in 1862 on continuous blockade duty, most of it on the Texas coast. During that time, her officers and crew had fresh provisions for just twenty-four days. When she was eventually relieved on station and returned to the fleet anchorage at the mouth of the Mississippi, some forty men—more than half her crew—were on the sick list with scurvy, dysentery and diarrhea. Afflicted vessels on the Texas blockade at various times included Brooklyn and, on at least two separate occasions, the bark William G. Anderson.
A friend of mine, a nautical archaeologist, likes to use a crude barnyard analogy involving nursing piglets to describe the difficulty of supply to USN vessels stationed off the Texas coast, a situation that contributed much to the prevalence of scurvy and other health problems among their crews. I won't repeat it here, though.