Why can a person eat spelt on a low FODMAP diet but not wheat? Spelt is a variety of wheat. Besides, I've seen some information suggesting spelt is higher in fructans than wheat.
Unlike a food sensitivity or allergy, when it comes to FODMAPs its not important whether the origin of the food is wheat, spelt, soy, corn etc. What matters is whether the product made with the commodity is high, medium or low in FODMAPs. In the case of wheat and spelt, fructans would be the main FODMAP of concern. It is irrelevant whether these foods contain gluten, as gluten is not a FODMAP.
A person can eat wheat products on a low FODMAP diet as long as they are low in fructans, for example we would expect wheat starch or wheat germ oil to be low in fructans due to processing, so they are suitable for a FODMAP elimination diet. Breads made with wheat have so far proved to contain too many fructans to be suitable on the elimination phase of the diet. I am hopeful we might someday have some data from Monash about breads made with traditional, two day sourdough fermentation methods. It seems possible they might be lower in fructans, if the microbes in the sourdough starter eat up most of the fructans for us. Several types of sourdough bread were included among the 80 loaves of bread from the US that my husband and I delivered to Monash University in 2013, but the results are as yet unpublished. It's also possible, though unproven, that sprouting grains could reduce FODMAP content.
(UPDATE: August, 2014: Although raw data has not been published, the latest Monash app update gives a "green light" to sourdough breads made from wheat flour, both white and whole wheat! These breads are suitable for the elimination phase of the diet. Great news for bread lovers! Updates for my teaching tools and books will suggest a limit of 2 slices per meal. Sprouted wheat breads were not low enough in FODMAPs to be suitable for the elimination phase of the diet)
As for spelt, which is indeed an ancient variety of wheat, several spelt products have now been analyzed for FODMAPs in the lab at Monash and the results of the HPLC and the Fructan Megazyme Kit data apparently demonstrate they are low in FODMAPs. I say apparently because they have been green-lighted in the Monash University Low FODMAP Diet App, although the actual nutrient data has not been published for all of them. Whether this can be extended to US spelt products remains to be seen.
It seems there is disagreement in the science about the fructan content of spelt. I have seen papers that analyzed fructans in wheat and spelt and found that the spelt was lower in fructans than wheat. Why the discrepancy the information you may have seen? Both papers might be "right." Differences may have to do with different cultivars of spelt. Slightly different example, but we know that wheat cultivars meant for growing in cold climates like North American are bred for higher fructan content than wheats meant for warmer climates. Perhaps the same could be true for spelt? Might vary also with a dry vs. wet growing season.
What has your experience been with spelt flour, spelt bread and sourdough spelt bread?