this is one reason why I use them...from
http://www.davedraper.com/fusionbb/showtopic.php?tid/4594/
"In a now classic experiment in the �50s, Dr. BH Ershoff demonstrated that liver extract was able to boost strength, endurance, performance, and resistance to stress and disease.
Ershoff took three groups of rats and fed them controlled diets for a 12 week period. Group 1 ate a basic diet fortified with vitamins and minerals. Group 2 ate as much as they wanted of the same diet plus B vitamins and brewer's yeast. Group 3 ate the basic diet but had 10% desiccated liver added to their rations.
The rats were then placed into a drum of water, which they could not climb out of. Therefore, it was literally either sink or swim. The Group 1 rats swam an average of 13.2 minutes before they all drowned. Group 2 swam an average of 13.4 minutes before meeting Group 1 at the ole Davy Jones' Locker. Group 3, however, were still swimming at the end of 2 hours, at which time the experiment was concluded, and the rats set free in a field nearby. Now, either the Group 3 rats had watched the fate of their classmates very closely, or the liver had something to do with them swimming almost 10 times as long."