GOS (galacto-oligosaccharides)
Fermentable fibers
The galactose sugars of legumes — raffinose, stachyose, verbascose. The ones that cause bloating, and the ones that feed.
Soaking then rinsing removes part of them: more digestible, but less nourishing for the microbiota. Drained and rinsed, canned legumes have lost a good share of them; increasing amounts gradually gives the gut time to adapt.
Effects and benefits
The sugars of legumes cause gas… and bifidobacteria. They are cousins of the sugars in breast milk, so much so that they are added to infant formula. And the discomfort fades: eaten every week, lentils and chickpeas cause less and less of it.
Raffinose, stachyose, verbascose: three sugars we cannot digest, for lack of one enzyme, alpha-galactosidase. Bacteria have it. They ferment them into hydrogen and carbon dioxide, hence the reputation of beans, but also into short-chain fatty acids, and bifidobacteria benefit.
A few grams are enough: in trials, GOS raised bifidobacteria within one to two weeks, more so at higher doses (Davis et al., 2010).
The discomfort is not inevitable. In a trial where adults ate half a cup of beans every day, about half noticed more gas in the first week; by the third, most saw no difference (Winham and Hutchins, 2011).
Breast milk contains more than two hundred oligosaccharides that feed the infant's bifidobacteria. GOS are simpler, but close enough to be added to infant formula to mimic this effect (Bode, 2012).
Sources: Davis et al., 2010 · Winham and Hutchins, Nutr J, 2011 · Bode, Glycobiology, 2012
Where to find it (32)
- Adzuki bean
- African yam bean
- Bambara groundnut
- Black bean
- Black chickpea
- Black lentil
- Black soybean
- Broad beans
- Chickpeas
- Cowpea / black-eyed pea
- Flageolet / borlotti bean
- GOS (prebiotic)
- Grass pea (cicerchia)
- Green / brown lentil
- Horse gram (kulthi)
- Kersting's groundnut
- Lablab bean
- Lima bean
- Lupin
- Moth bean (matki)
- Mung bean
- Peas
- Petai (stink bean)
- Pigeon pea
- Red kidney bean
- Red lentil
- Rice bean
- Santorini fava
- Soybeans / edamame
- Split peas / dried green peas
- Urad bean
- White bean
Also, in smaller amounts (30)
- Achi
- Akparata
- Amphicarpaea
- Beach pea (Vigna marina)
- Bitter vetch
- Buhu
- Chachafruto
- Creeping bauhinia
- Desert ironwood
- Ground plum
- Guaje
- Hairy tare
- Jengkolan
- Jering (dogfruit)
- Kalahari bauhinia
- Marama bean
- Mesquite
- Minni payaru
- Néré seeds (African locust bean)
- Okie bean (Cape pea)
- Okpiye
- One-flowered vetch
- Palo verde
- Runner bean
- Siberian peashrub
- Tara nut of Madagascar
- Tepary
- Ugba (oil bean)
- Vatovaea
- Velvet bean