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By Matthew Rees

Food and Health Fact #151: Demystifying beans, health, and flatulence

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Legumes and pulses – fancy ways of saying “beans” – are among the world’s most nutrient-rich foods. They are high in fiber, iron, folate, calcium, potassium, phosphorus, and zinc, but low in calories and fat. The National Library of Medicine (part of the National Institutes of Health) adds that, “The body uses the carbohydrates in legumes slowly, over time, providing steady energy for the body, brain, and nervous system.”

Legumes also have a greenhouse gas footprint that is 90 percent lower than that of beef and 80 percent lower than that of lamb (per 100 grams of protein) and they tend to be extremely affordable.

But per capita, Americans eat them in small numbers compared to the residents of other countries (see chart below). Why?

“Many consumers avoid eating beans, such as pinto, black, and kidney, because they fear that excessive intestinal gas or flatulence may result,” observed the authors of a 2011 paper on the topic. The fear is captured in an age-old limerick: “Beans, beans, they're good for your heart. The more you eat them, the more you fart.” 

But the perception doesn’t quite match reality. The study underpinning the 2011 paper involved daily consumption of either pinto beans, black-eyed peas, or baked beans for eight consecutive weeks. The authors found that:

[O]nly half or fewer of the participants experienced the sensation of having more gas in the first week of diet change. Seventy percent or more of the participants who experienced flatulence felt that it dissipated by the second or third week of bean consumption. The black-eyed peas with lower fiber content elicited less of a response in most people in comparison to the pinto and navy beans with higher fiber content.

Thus the authors’ conclusion: “clinicians are in a good position to emphasize that the flatulence will decrease over time if bean consumption is continued and that the nutritional attributes of beans in the diet outweighs the potential for transitory discomfort.”