Whilst i agree with you fully everyone is different, i believe the Adrenals are massive key factors as with adrenal burnout always IMO their is case of low thyroid, if you have low thyroid then you have low immunity.
99% of any cure posts in here seem to involve the key that i stopped worrying about being ill, i stopped thinking about food and just enjoyed the healthy food rather than restrictive diets etc.
The adrenals can be mass factors in determining health esp gastro secretion to break down food etc.