Oligosaccharides

What is it?

Oligosaccharides are the O of FODMAP, and there are two families: fructans, in wheat, onion, garlic and artichoke, and galacto-oligosaccharides or GOS, in legumes — lentils, chickpeas, beans. Humans have no enzyme for either, so both reach the colon intact and are fermented by gut bacteria, producing gas, bloating and changes in stool. That is not a defect of digestion: nobody digests them.

Which vegetables carry the most fructans

Muir (2007) measured total fructans in 60 vegetables and 43 fruits and found the highest in garlic, artichoke, shallots, leek bulb and onions — a range of 1.2 to 17.4 g per 100 g given ACROSS those five rather than for any one of them. The abstract does not rank them against one another, so membership of the top group is what it supports, not an order inside it. Hogarth (2000) separated three fructooligosaccharide oligomers by ion chromatography and found that of the vegetables investigated, ARTICHOKES contained by far the most FOS, followed by onion and banana — a ranking and a method, with no figure per 100 g.

A botanical family is not a food

Campbell (1997) ordered foods and feeds by plant family and found the Compositae highest in total FOS, followed by the Allium species of the Amaryllidaceae. Compositae is artichoke, chicory and their relatives; Allium is onion, garlic and leek. Giving a single member its family's rank is not something that study supports, and it publishes no per-food value.

Grams per portion, for grain products

Biesiekierski (2011) reported fructan per portion as eaten across 55 grains, cereals, breads, pulses and biscuits: couscous highest at 1.12 g, wheat-free muesli 0.96, a muesli fruit bar 0.81, dark rye bread 0.60, oats 0.11, spelt bread 0.07. Only the eight foods its abstract names carry a figure. Whelan (2011) measured fructan in UK breads at 0.61 to 1.94 g per 100 g, with rye bread richest at 1.94 and gluten-free bread at 1.00 — about the same as the others.

What a whole diet supplies

Moshfegh (1999) used the USDA food-intake survey across more than 15,000 Americans and found an average of 2.6 g of inulin and 2.5 g of oligofructose a day, from 1.3 g in young children to 3.5 g in teenage boys. It is an intake survey and publishes no per-food content, and its shares describe the American diet of the mid-1990s.

Soy, where ripeness and fermentation change the answer

Jiang (2020) compared 54 edamame genotypes against the mature soybean of the same line and found the MATURE soybean highest in stachyose and total sugars — a direction rather than an absolute figure, since the abstract quantifies only sucrose. Rehms and Barz (1995) screened 46 tempe-forming Rhizopus strains and found R. oryzae and R. stolonifer consuming raffinose, stachyose and melibiose completely; that measures the fungi rather than a finished tempeh, with no before-and-after content for anything on sale. Soaking and cooking legumes thoroughly, and keeping onion and garlic out of an early reintroduction phase, follow from all of the above.

Source: Muir J.G. et al. (2007), for total fructans in 60 vegetables and 43 fruits, the 1.2-17.4 g/100 g range given across five vegetables rather than per food; Hogarth A.J. et al. (2000), for the artichoke-onion-banana FOS ranking, a ranking with no figure per 100 g; Campbell J.M. et al. (1997), for the ordering by plant family — Compositae then Allium — which is not a ranking of individual foods; Biesiekierski J.R. et al. (2011), for fructan per portion as eaten in 55 grain products and pulses, of which the abstract names eight; Whelan K. et al. (2011), for fructan in UK breads; Moshfegh A. et al. (1999), for inulin and oligofructose in a whole diet — an intake survey with no per-food content; Jiang G.-L. et al. (2020), for mature soybean against edamame, a direction and not an absolute figure; Rehms H. & Barz W. (1995), for Rhizopus consuming the raffinose family — it measures the fungi and not a finished tempeh

Frequently asked questions