No - wrong
i disagree with the fundamental basis of this question. in fact i see this as a problem at curezone.
if i am wrong about a health issue, then i am simply wrong. there is no prophet/false prophet issue to deal with.
if i tell you God wants us all to take this attitude, or to believe that, or to treat our fellow man in this way, then you could judge me as being a true or false prophet.
nutrition is not religion, and when you make a religion out of your nutritional opinions you go down a dangerous road. this is what some ppl do. they get convinced that substance X is good to ingest, then they conclude that God agrees with this statement. then they see all who disagree with ingesting substance X as disagreeing with God. they see the promotion of substance X as some kind of divine calling. they rail and rage against all who disagree with them about substance X, and secretly imagine them to agents of Lucifer. when they argue with others about substance X they have lost all ability to be moderate or balanced - afterall God wants us all to digest this substance!!
then they begin imagining that their opinions on other matters of health are in fact divine revelatons. etc etc etc
if you are wrong about a matter of nutrition, you are just wrong. thats all.
now, if you KNOW that substance Z is harmful, and you convince the government to legalize it anyway cause you stand to make a few million off of it, then thats morally wrong. but its wrong because you INTEND to HARM others, not because of your stance on a nutritional matter.
religion is religion, nutrition is nutrition. when you make a religion out of your nutrition, you are bound to do more harm than good.