While all organ meats contain a wealth of health-promoting nutrients. Liver in particular contains a very special benefit known as "anti-fatigue factor" that makes it a favorite with athletes and others seeking a natural energy boost.
Benjamin K. Ershoff, PhD, in July, 1951 conducted an experiment where he divided laboratory rats into three groups and supplemented the third group with powdered liver.
After several weeks, the animals were placed one-by-one into a drum of water in order to see how long they could swim before needing to be removed. The first group swam for an average 13.3 minutes before giving up. The second group, which had added fortifications of B vitamins, swam for an average of 13.4 minutes. Of the group receiving liver, three swam for 63, 83 and 87 minutes while the other nine rats in this group were still swimming vigorously at the end of two hours when the test was ended. Something in the liver had prevented them from becoming exhausted.
To this day scientists have not been able to pinpoint this anti-fatigue factor in liver.