A recent report suggested that the use of cod liver oil may improve outcomes in those under treatment for TB. One speculation is that the oil, high in vitamin D, may be the most important and immune enhancing agent. Deficiencies of vitamin D are widespread, particularly among African Americans in general and people living with HIV in particular.
Note that cod liver oil also has significant amounts of vitamin A and the omega-3 fatty acids found in other fish oils. It may well be the combination of these agents that may help to improve outcomes and possibly act as a prophylaxis against tuberculosis–as well as being salutary for health in general!