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1) Before I was went on a gluten-free diet, though I had lots of other
problems, I very rarely had a cold and such colds as I did have tended
to be mild. There are a number of studies in the scientific literature
showing an enhanced cellular immune system in celiacs.
2) There is a continuing debate about Blastocystis hominis. My own
opinion (I am a medical microbiologist of some 40 years experience) is
that the case for it causing any significant disease is very weak. I'd
tend to agree with the conclusion of one of the most thorough
researchers on the subject that if you find Blastocystis it should be a
cue for looking for some other cause of intestinal pathology (which
could include gluten intolerance).