Can you De-Gas Beans?

This is an excerpt from Russ Parsons’ L.A. Times article about whether or not how you cook beans can reduce their gas producing tendencies.

There is no getting around it — beans cause flatulence. The degree to which different beans affect different people varies, but the truth is inescapable. And there seems to be little a cook can do about it.

Whether to soak beans prior to cooking or not is simply a culinary question. It may shorten the cooking time, but other than that, there’s no effect [on flatulence].


“Whether to soak beans prior to cooking or not is simply a culinary question,” says Gregory Gray, who has been studying beans for 10 years at the U. S. Department of Agriculture’s Western Regional Research lab in Albany, Calif. “It may shorten the cooking time, but other than that, there’s no effect [on flatulence].”

Louis B. Rockland, who has been studying beans even longer — first at Albany and now with his own research firm, Food Tech Research in Placentia, concurs. “There are lots of old wives’ tales [about reducing flatulence] — people use bicarbonate of soda, ginger, sulfur, castor oil — a whole series of them. But there’s no evidence that any of them — including soaking — work effectively.”

The problem with beans is well documented. At its root are two factors. First, beans are high in fiber, which most Americans don’t eat much of and which can cause flatulence. Second, beans contain complex sugars called alpha-galactosides. The human body does not produce enzymes to digest these sugars. Mainly raffinose and stachyose, they pass through the stomach undigested until they reach the large intestine. There they ferment, producing gases — hydrogen, carbon dioxide and — in some people — methane. The rest is faux pas.

It was thought that soaking beans in cold water leached these sugars out of the bean. Throw away the water and you throw away the gas — it has a simple appeal. Unfortunately, it isn’t true. These sugars are part of what the bean uses for nourishment as it grows into a plant, and the bean does not part with them gladly.

“When you soak beans in cold water, the beans are actually still alive and their cell walls are still functional,” explains Gray. “Those walls are designed to be a very good barrier — to take water in, but not to let the seed nutrients out.”

Gray and his colleagues developed a method for extracting most of the alpha-galactosides from beans. The beans are boiled for three minutes (effectively killing the bean and allowing the sugars to pass through the cell walls), then allowed to stand for two hours. That water is poured off and the beans are covered and soaked for another two hours. Then they’re drained, covered and soaked another two hours before being drained and rinsed a final time.

This method succeeded in ridding the beans of 90% of the troublesome sugars, but as you might expect, there was a side effect. “I used to do this blanch-soak method all the time at home and it works very nicely,” Gray says. “The one thing people who ate dinner with us have noted is that you do lose some flavor.”

What’s more — without going into details of what they measured and how — suffice it to say that even with almost all of the alpha-galactosides gone, there wasn’t a consistent marked decrease in human flatulence.

“We reduced the alpha-galactoside content by 90% but we haven’t done anything to dietary fiber,” says Gray, “and dietary fiber produces similar effects.”

This casts doubt not only on this particular pre-soaking method but also on the effectiveness of enzyme additions, such as Beano, which supposedly supply the chemicals necessary to break down the problem sugars.

In fact, it seems, the surest cure for flatulence caused by beans is eating more beans.

“Apparently, if you eat beans regularly, the microflora [which ferment the sugars causing gas] adjust somewhat,” says Gray. “If you eat bean-and-cheese burritos every day, unless you have some kind of specific problem, you probably won’t notice it at all. In cultures that routinely eat beans, you don’t hear a lot of complaining about flatulence.” 

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