This is inaccurate.
I have a significant gastrointestinal condition as well which Nillson reportedly has. Notice I use the word has. Such conditions are not cured as such they are in remission with a combination of dietary, lifestyle, and supplements. it takes absolute dedication to purpose to even minimize the conditions. Virtually any significant gastrointestinal condition I am aware of is exacerbated by stress. You can be doing all parts of your regimen faithfully and still suffer ill effects and relapse due to stress. Millions of people suffer though conditions like this fairly silently.
To say that a significant GI condition is just treated with B12 is so off the mark. That's just the start of it. The likely REASON he would be deficient in B12 (and probably multiple other vitamins and minerals) is due to the gastrointestinal condition not allowing proper uptake of nutrients from the consumed diet. Again you can be eating all the ideal foods and not have uptake. Many people have profound difficulty even uptaking vitamins from supplements. Sometimes extensive work has to be done replenishing/reconstituting gastrointestinal flora/bacteria to even approximate normative digestion.
Stress is a major kick in the nuts for almost anybody with a wide range of diagnosed gastrointestinal conditions. Get overwhelmed with stress and relapse is all but guaranteed. I would say particularly in a patient experiencing vitamin B types of uptake difficulty as components of vitamin B can help in alleviating stress, anxiety, and depression.
ps and I can't even eat a snickers bar if I wanted to, which explains sooooo much..