Also, there is no serious evidence that vaccines, MSG, GMOs, or similar cause autism. Nor is there evidence that homeopathy or a multiple week fast helps. Homeopathy is in fact no better than a placebo at anything.

Y
ou're mistaken with regard to the vaccines.  There was a whistleblower who recently released a bunch of docuмents in which the CDC clearly knew about the strong vaccine->autism link, especially with MMR.

Even with non-GMO, pesticide-free, or organic flour?Quinoa, which is gluten-free and thus low-glycemic, is very good; it's the only grain that provides all the amino acids ("complete 'protein'").

Also, St. John Chrysostom said Christ and His disciples ate nothing more than barley bread.

Quinoa is great!  I eat it regularly.  However, strictly speaking, it's not a grain.  But close enough.

As for barley, no disrespect intended, but how would St John Chrysostom have known this?  And am I correct in understanding that the bread for Passover, or for the meal that preceded Passover and was the first Mass, had to have been wheat, not barley, not anything else?

I like barley as one of the grains in multigrain bread, and of course as the central ingredient in beer --- its "highest and best use".

Also, St. John Chrysostom said Christ and His disciples ate nothing more than barley bread.

I, too, question how Chrysostom, born 3 centuries after the Resurrection (i.e., born c. 347), could've known that they "ate nothing more" than barley bread.  But he was an early Doctor of the Church, so I wouldn't rule out that detail being Divine revelation.

As for barley, no disrespect intended, but how would St John Chrysostom have known this?  And am I correct in understanding that the bread for Passover, or for the meal that preceded Passover and was the first Mass, had to have been wheat, not barley, not anything else?

Actually, you're not correct.  Passover had at least 1 mundane agricultural aspect: It coïncided with the harvest of barley in the Holy Land.  To maintain that coïncidence despite the disconnection of seasons from the lunar calendar used by the Hebrews, 2nd-Temple rules allowed a committee of 3 Temple officials to reschedule Passover based on local field observations.  What kind of observations?  Specifically, whether the barley in the fields at Jerusalem was close enough to harvest.  What about wheat?  In the ancient times of the Christ on Earth, it was what we might call the "upscale grain" for bread, and it didn't mature until later in the year.  Its harvest coïncided with the Hebrew Pentecost, observed 50 days after Passover.[#]

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Note #: St. Joseph (Textbook) Edition of the Holy Bible, O.T. p. 164 (Nm. 28:26) note "28,26" (a single note).  Those 50 days are counted inclusively, as also done by the Romans, so it was exactly 7 weeks later by modern reckoning.