In the absence of meat, common black beans are a primary source of protein, minerals and vitamins in much of the developing world. But beans are notoriously hard to digest, failing to freely release many of their nutrients in the gut. Now researchers have discovered that fermenting beans with two strands of common bacteria free up many more nutrients and make the legumes easier to digest.

Marisela Granito and Glenda Alvarez of Simon Bolivar University in Venezuela have shown that fermenting beans--allowing natural bacterial cultures to develop and break down the raw food--reduces the number of indigestible compounds. Such lactic acid bacteria are already used to help create products like yogurt. In the case of beans, Lactobacillus casei and Lactobacillus plantarum combine to remove fibers and make more nutrients available, according to the research presented in today's Journal of the Science of Food and Agriculture.

In fact, the bacteria increased the proportion of nitrogen absorbed by rats fed the fermented and cooked beans while reducing soluble and insoluble fibers by 63 and 39 percent respectively. Such fibers in unfermented beans end up being digested by bacteria in the human gut, which then release methane. That means that such processing helps make beans both more nutritious and less likely to produce flatulence.