1) Sourdough, specifically 24 hour fermented sourdough, has been shown to be better for people who have gluten issues, though not celiac specifically.

2) in most reports, bread was made with freshly ground flour that had been sifted to have most of the bran removed, then soured for sourdough, then baked, and then eaten for a week. Most households were not baking bread every day.

3) Dr. Weston Price found that most of the time, bread was eaten with lots of fat soluble vitamins, usually butter and/or cheese. I think one of the quotes said something like the Swiss would eat a slice of bread and a slice of cheese for lunch, with the cheese being as big as the bread.

4) In my opinion, most of the gluten and grain issues are from altered gut flora, which has been getting progressively worse. So, a 1400s bread with a 1400s stomach would do a lot better than current bread with current stomachs.

Likely to be less allergic to the older strains of wheat.

Actually, I would think that it would be worse ( from the perspective of the flour) -- much in the same way that white rice is better than wild rice since the processing removes many of the anti-nutrients (like wheat germ).

That being said, I got a recipe book from my grandmother that is circa 1920. There less than half of the sugar than my modern recipe book

Thus it maybe less dangerous, but it is not the flour that would make it so.

Better but not healthy

You don't even need to go to the 1400's. Pre-1975 wheat is different than today's wheat. Check out the book "Wheat Belly" for coverage of the different types of wheat and how new wheat is likely the reason for the uptick in celiac. He cites a cool study where they use new testing techniques on old blood (from the 50's) and there were actually fewer celiacs then compared to now - so he ruled out better tests for the higher rates. New wheat had much more bad stuff than old wheat. But old wheat is still terrible for you even of you can find it.

There was a thread recently on ancestral wheats:

http://paleohacks.com/questions/152954/pre-1970-strain-of-wheat-is-it-available#axzz29ZXBjYmn

[and adding later: there's also an article on wheat today on mark's daily apple that explains many of the differences in old & new wheat production & processing:]

http://www.marksdailyapple.com/the-problems-with-modern-wheat/#axzz29fMR709n

It could go either way. Better because it would be organic, less processed, etc. Worse because of the food storage & contamination issues. I heard a story about a town in France or someplace, in the Middle Ages or so, where a bunch of people went nuts for a while, having hallucinations and so on. At the time it was attributed to possession, speaking in tongues and that sort of thing. Since then someone figured out that a fungus had gotten into the flour.

Better, but still not better than the worst of some other real food (boneless, skinless chicken breast, conventional dairy, conventional fruit + veggies, even peanuts gasp!). In that day, it'd probably keep you alive a bit longer, but you certainly wouldn't thrive on it.

More nutritious? Probably not. Less toxins, more digestible? Again, probably not. We shouldn't dismiss modern plant breeding, nor should folks pine for the past...