Island Man,
In the earlier days of Watchtower's blood transfusion taboo the religion's leadership leveraged nutritional gain as the reason why JWs should be concerned with the therapy. Then it admitted it was pointless to argue that transfusion was a means of providing nutrition. The latter was said point-blank by Watchtower in a letter to one of its appointed elders.
I just added an article to my blog highlighting this at: Nutrition or not? Not! So what?