In reference to my post on soaking legumes and reducing oligosaccharides, a reader asked me if there has been any research on the efficacy of Solgar’s Vegetarian Digestive Aid.
In my research on soaking beans and reducing oligosaccharides, I didn’t come across any study using a battery of digestive enzymes such as what is contained in Solgar’s preparation. Solgar’s Vegetarian Digestive Aid does not contain the digestive enzyme considered most effective at reducing flatulence from beans, alpha-galactosidase. Bean-zyme, a vegan version of Beano, contains alpha-galactosidase, as does Deva’s Vegan Digestive Support.
In their article, Effective Management of Flatulence, American Family Physician provides a chart comparing the effectiveness of various methods. They rank a couple of probiotic preparations as being highly effective, and slightly more effective than a large dose of alpha-galactosidase (they cite reference 1 below). The large dose, 1200 GaIU, would be the equivalent of 8 Bean-zyme tablets. A smaller dose of 300 GaIU, the equivalent of 2 Bean-zyme tablets, was also somewhat effective.
I found one other study (2) measuring the effectiveness of alpha-galactosidase, in which it did not seem quite as effective, but they were using drops rather than tablets and I’d be concerned about the drops themselves being digested before they could take effect.
As an aside, in preparing legumes, they can be treated with enzymes that will remove all of the oligosaccharides, but I’m not aware of a practical way for people to do that at home.
I think there might have to be a Part 3 (and, who knows, maybe a Part 4, 5, and 6) to deal with all the questions regarding soaking foods. I might not do them in consecutive posts.
The flatulence caused by eating beans is normally attributed to the oligosaccharide content of the beans. Oligosaccharides are chains of sugar molecules, usually two to ten in length, and comprising of at least some sugars other than glucose. (Long chains of glucose-only molecules are considered starches and are typically easy to digest.)
The flatulence is caused by the fact that humans do not have digestive enzymes to break down the oligosaccharides and, instead, they are broken down by bacteria in the lower intestines which produce gas in the process.
Soaking reduces the amount of oligosaccharides in beans. But how does it compare to simply cooking? Unfortunately, in the time I had to search, I did not find a study that compared soaking and cooking to only cooking. But I did find a study that compared the oligosaccharide reduction in pinto beans among different preparation methods (1):
- Soaking for 18 hours: 10% reduction
- Soaking for 18 hours, then boiling for 90 minutes: 50% reduction
- Soaking for 18 hours, then autoclaving for 30 minutes: 57% reduction
Autoclaving is approximately the same as pressure-cooking.
It’s not clear from this study that you first need to soak the pinto beans to produce the 50% reduction in oligosaccharides.
In her article on reducing flatulence in veg diets, Dina Aronson, MS, RD suggests, “If you make beans from scratch, soak them overnight first, rinse them well, and rinse them several times during the cooking process, as this will help get rid of more of the gas-causing oligosaccharides. Also, the longer you cook beans (with rinsing), the better.”
It should also be noted that in their comments, the authors of the study above say, “Soaking of Great Northern, kidney, and pinto beans and their subsequent boiling for 90 min decreased the amount of [the oligosaccharides] raffinose and stachyose by 70-80%. In marked contrast, sucrose, raffinose, stachyose, and verbascose contents increased [emphasis added] following the cooking of red, Bengal, black, and green grams (1).”
Sigh. Luckily, I don’t think too many of us eat “grams,” so we probably don’t need to worry about that. I looked up the study and they did not soak the beans before cooking, so perhaps that was the problem (2).