What you say is certainly possible, but nonetheless I find it hard to believe that this has happened in reality.
The reason is that the non-existence of gluten-free food was not restricted to the Antiquity and the Middle Ages, but in many places it remained true e.g. a half century ago.
Where I was born, in Eastern Europe, among the millions of citizens, there was no normal human who would not ingest a lot of gluten every day, but child mortality was very low and the incidence of celiac and similar diseases was low enough that the general public was completely unaware that such diseases even exist.
Moreover, there are published studies that conclude that at least during the last few decades the frequency of gluten-caused illness has been increasing.
The reason is that the non-existence of gluten-free food was not restricted to the Antiquity and the Middle Ages, but in many places it remained true e.g. a half century ago.
Where I was born, in Eastern Europe, among the millions of citizens, there was no normal human who would not ingest a lot of gluten every day, but child mortality was very low and the incidence of celiac and similar diseases was low enough that the general public was completely unaware that such diseases even exist.
Moreover, there are published studies that conclude that at least during the last few decades the frequency of gluten-caused illness has been increasing.