I'm glad your mother is fit and healthy
Many who eat wheat are not.
Some people don't have any problems with wheat, some do.
Research estimates that 1 in 133 have celiac disease. [1] most don't know it and many are asymptomatic.
Along with celiac disease there is gluten intolerance, which has similar symptoms (pain, gas, bloating, diarrhea) but not damage to the intestines.
And along with that it has been demonstrated that gluten (gliaden – a protein in gluten) causes in increase in intestinal permeability which may lead to or contribute to many other health conditions,
And along with that any bacterial imbalance will be fuelled by the abundance of food provided by grain.
The hybridised and GM varieties we eat today have significantly higher levels of gluten than older varieties, leading to a larger number of people with symptoms.
It seems to be a combination of genetics, exposure, and gut bacteria. (there are documented cases of elderly ladies developing celiac disease in their seventies, there genes haven't changed, there diets were the same so it is thought that a change in gut bacteria left them with an immune response to gluten - antibiotics? stress? some change of diet?)
"Gliadin is a strange protein that our enzymes can’t break down from the amino acids (glutamine and proline) into elements small enough for us to digest. Our enzymes can only break down the gliadin into peptides. Peptides are too large to be absorbed properly through the small intestine. Our intestinal walls or gates, then, have to separate in order to let the larger peptide through. The immune system sees the peptide as an enemy and begins to attack. The difference is that in a normal person, the intestinal walls close back up, the small intestine becomes normal again, and the peptides remain in the intestinal tract and are simply excreted before the immune system notices them. In a person who reacts to gluten, , the walls stay open as long as you are consuming gluten. How your body reacts depends upon how long the gates stay open, the number of “enemies” let through and the number of soldiers that our immune system sends to defend our bodies. "
Alessio Fasano, M.D., Medical Director for the Center for Celiac Research
For any illness the first place to look is food, the second place is a pharmaceutical company.
[1] Celiac Disease Facts and Figures
http://www.uchospitals.edu/pdf/uch_007937.pdf