George tells in his book about the methodology of trials before the 1970s when Swank started his study, mentioning "The chopped liver diet" for which George Whipple won Nobel prize in medicine.

I accidentally came across his name and looked him up in Wikipedia. It's interesting and puts Swank's methodology into perspective. Swank, however must have been too stubborn to publish in the first 10 or 20 years - or he felt that given the nature of the disease, it would take that long to determine if it really worked.

Here's the link and a little bit from the article

Whipple's main research was concerned with anemia and with the physiology and pathology of the liver. He won the Nobel Prize for his discovery that liver fed to anemic dogs reverses the effects of the anemia. This remarkable discovery led directly to successful liver treatment of pernicious anemia by Minot and Murphy. Before that time, pernicious anemia had been truly pernicious in that it was invariably fatal.

In presenting the Nobel Prize in Physiology or Medicine in 1934, Professor I. Holmgren of the Nobel committee observed that "Of the three prize winners, it was Whipple who first occupied himself with the investigations for which the prize is now awarded. ... Whipple's experiments were planned exceedingly well, and carried out very accurately, and consequently their results can lay claim to absolute reliability. These investigations and results of Whipple's gave Minot and Murphy the idea that an experiment could be made to see whether favorable results might also be obtained in the case of pernicious making use of the foods of the kind that Whipple had found to yield favorable results in his experiments regarding anemia from loss of blood."