According to the USDA Nutrient Database for Standard Reference, coffee does not contain fiber, and would therefore FODMAPS-friendly. However, I have just become aware of some recently published details about the nutrient composition of coffee (J Agric Food Chem, 2007, 55, pgs 1999-2003).
According to this report, the average 9-ounce "cup" of filtered coffee contains 1.3 grams of fiber. Most of the fiber is a fermentable type, and would be defined as FODMAPS, in the galactans category. People who drink three "cups" of coffee a day could be consuming about 4 grams of fiber, equal to the amount in 1/4 cup of cooked beans. Who knew?
Many people, including me, would find it very difficult to give up coffee entirely for even a week or two, to do a completely FODMAPS-free elimination phase. I'm going to suggest, instead, that people undertaking the FODMAPS elimination diet cut back on coffee somewhat, but not to the point that would cause caffeine withdrawal symptoms, during the elimination phase.
If you decide to be a purist, you could wean yourself off coffee over a week's time--watch out for rebound caffeine-withdrawal headaches if you do this. Then, after the elimination phase of the diet, you could add de-caf coffee back during the galactans challenge. Challenge with decaf to avoid confusion about the impact of caffeine itself on bowel habits.
Once in a while someone who is apparently a good candidate for the FODMAPS elimination diet doesn't improve much during the elimination phase. Before calling the experiment a failure, it might make sense at that point to completely wean off coffee and see if any further improvement takes place.
