The solution for celiac is to never ingest wheat, barley or rye. The solution for Tropical spru is to relocate to an area without spru ~ usually further North.
Still, spru can be moderated with the administration of a number of anti-biotics. Cutting out wheat, barley and rye has only a modest benefit.
There is a latitude gradient involved in both conditions ~ probably not as pronounced as with the diseases discussed in these articles, but it's there.
MS has been linked to latitude as well.