Gastrointestinal disturbances are extremely common. Many foods for many reasons can cause gastrointestinal disturbances and soyfoods are not exceptions in this regard. For example, allergic reactions to foods can lead to gastrointestinal disturbances in some cases1 although allergy to soy protein is quite rare, occurring in only an estimated one of 2500 adults.2 Like all beans, soybeans contain oligosaccharides, which are small sugars not able to be digested by intestinal enzymes. As a result, they are metabolized by intestinal bacteria, which can cause flatulence, bloating and intestinal discomfort in some people.3 For such people, fermented soyfoods (e.g. miso or tempeh) may be a good choice since fermentation reduces oligosaccharide content, which reduces flatulence.3,4 In many traditional and modern unfermented soy products, the oligosaccharides are largely removed. Furthermore, soybean oligosaccharides may function as prebiotics by increasing the number of friendly bacteria in the gut.5
One analysis of the scientific literature found that in response to soy protein, there were 56 gastrointestinal complaints out of 515 study subjects, for a prevalence of about 10.8 percent.6 However, in response to casein (milk protein), there were 61 complaints out of 442 subjects, for a prevalence of 13.8 percent. Notably, the amount of protein fed to the subjects in these studies was typically far more than one would normally consume.
Soybeans are also rich source of isoflavones, a group of naturally-occurring plant chemicals also referred to as phytoestrogens. Isoflavones are being studied for a range of health benefits but could contribute to gastrointestinal disturbances in some people. One large analysis found that out of over 5000 women, 17.9% complained of gastrointestinal disturbances. However, in the placebo or control group, nearly as many reported similar symptoms – 13.4%.6 Because the studies included in this analysis sometimes provided isoflavones alone and sometimes soy protein containing isoflavones, it isn’t possible to know precisely what may have led to the symptoms. More importantly, since such a high percentage of the subjects in the placebo or control group reported gastrointestinal symptoms, these data indicate that most of the symptoms in response to soy weren’t actually related to soy consumption.
In conclusion, the reason any given person may experience gastrointestinal problems in response to the consumption of soyfoods is unclear. Fortunately, the vast majority of people are able to enjoy soy products without any problems. Those experiencing problems may want to try different types of soy products to see if some work better than others.
Featured Expert
Mark Messina
Dr. Messina is the co-owner of Nutrition Matters, Inc., a nutrition consulting company, an adjunct associate professor at Loma Linda University, and the Executive Director of the Soy Nutrition Institute. Full bio >>
References:
1. Butkus SN, Mahan LK. Food allergies: immunological reactions to food. J. Am. Diet. Assoc. 1986, 86, 601-8.
2. Vierk KA, Koehler KM, Fein SB, Street DA. Prevalence of self-reported food allergy in American adults and use of food labels. J. Allergy Clin. Immunol. 2007, 119, 1504-10.
3. Suarez FL, Springfield J, Furne JK, Lohrmann TT, Kerr PS, Levitt MD. Gas production in human ingesting a soybean flour derived from beans naturally low in oligosaccharides. Am. J. Clin. Nutr. 1999, 69, 135-9.
4. Feng S, Saw CL, Lee YK, Huang D. Novel process of fermenting black soybean [Glycine max (L.) Merrill] yogurt with dramatically reduced flatulence-causing oligosaccharides but enriched soy phytoalexins. J. Agric. Food Chem. 2008, 56, 10078-84.
5. Bang MH, Chio OS, Kim WK. Soyoligosaccharide increases fecal bifidobacteria counts, short-chain fatty acids, and fecal lipid concentrations in young Korean women. J Med Food. 2007, 10, 366-70.
6. Balk E, Chung M, Chew P, Ip S, Raman G, Kuplenick B, Tatsioni A, Sun Y, Wolk B, et al. Effects of soy on health outcomes. Evidence report/technology assessment No. 126 (prepared by Tufts-New England Medical Center Evidence-based Practice Center under Contract No. 290-02-0022.) AHRQ Publication No. 05-E024-2. Rockville, MD Agency for Healthcare Research and Quality, July 2005.
ANSWERED QUESTIONS
Is the use of soyfoods associated with gastrointestinal disturbances?
Answered by Mark Messina, PhD, MS - February 10, 2011
Gastrointestinal disturbances are extremely common. Many foods for many reasons can cause gastrointestinal disturbances and soyfoods are not exceptions in this regard. For example, allergic reactions to foods can lead to gastrointestinal disturbances in some cases1 although allergy to soy protein is quite rare, occurring in only an estimated one of 2500 adults.2 Like all beans, soybeans contain oligosaccharides, which are small sugars not able to be digested by intestinal enzymes. As a result, they are metabolized by intestinal bacteria, which can cause flatulence, bloating and intestinal discomfort in some people.3 For such people, fermented soyfoods (e.g. miso or tempeh) may be a good choice since fermentation reduces oligosaccharide content, which reduces flatulence.3,4 In many traditional and modern unfermented soy products, the oligosaccharides are largely removed. Furthermore, soybean oligosaccharides may function as prebiotics by increasing the number of friendly bacteria in the gut.5
One analysis of the scientific literature found that in response to soy protein, there were 56 gastrointestinal complaints out of 515 study subjects, for a prevalence of about 10.8 percent.6 However, in response to casein (milk protein), there were 61 complaints out of 442 subjects, for a prevalence of 13.8 percent. Notably, the amount of protein fed to the subjects in these studies was typically far more than one would normally consume.
Soybeans are also rich source of isoflavones, a group of naturally-occurring plant chemicals also referred to as phytoestrogens. Isoflavones are being studied for a range of health benefits but could contribute to gastrointestinal disturbances in some people. One large analysis found that out of over 5000 women, 17.9% complained of gastrointestinal disturbances. However, in the placebo or control group, nearly as many reported similar symptoms – 13.4%.6 Because the studies included in this analysis sometimes provided isoflavones alone and sometimes soy protein containing isoflavones, it isn’t possible to know precisely what may have led to the symptoms. More importantly, since such a high percentage of the subjects in the placebo or control group reported gastrointestinal symptoms, these data indicate that most of the symptoms in response to soy weren’t actually related to soy consumption.
In conclusion, the reason any given person may experience gastrointestinal problems in response to the consumption of soyfoods is unclear. Fortunately, the vast majority of people are able to enjoy soy products without any problems. Those experiencing problems may want to try different types of soy products to see if some work better than others.
Featured Expert
Dr. Messina is the co-owner of Nutrition Matters, Inc., a nutrition consulting company, an adjunct associate professor at Loma Linda University, and the Executive Director of the Soy Nutrition Institute. Full bio >>
References:
1. Butkus SN, Mahan LK. Food allergies: immunological reactions to food. J. Am. Diet. Assoc. 1986, 86, 601-8.
2. Vierk KA, Koehler KM, Fein SB, Street DA. Prevalence of self-reported food allergy in American adults and use of food labels. J. Allergy Clin. Immunol. 2007, 119, 1504-10.
3. Suarez FL, Springfield J, Furne JK, Lohrmann TT, Kerr PS, Levitt MD. Gas production in human ingesting a soybean flour derived from beans naturally low in oligosaccharides. Am. J. Clin. Nutr. 1999, 69, 135-9.
4. Feng S, Saw CL, Lee YK, Huang D. Novel process of fermenting black soybean [Glycine max (L.) Merrill] yogurt with dramatically reduced flatulence-causing oligosaccharides but enriched soy phytoalexins. J. Agric. Food Chem. 2008, 56, 10078-84.
5. Bang MH, Chio OS, Kim WK. Soyoligosaccharide increases fecal bifidobacteria counts, short-chain fatty acids, and fecal lipid concentrations in young Korean women. J Med Food. 2007, 10, 366-70.
6. Balk E, Chung M, Chew P, Ip S, Raman G, Kuplenick B, Tatsioni A, Sun Y, Wolk B, et al. Effects of soy on health outcomes. Evidence report/technology assessment No. 126 (prepared by Tufts-New England Medical Center Evidence-based Practice Center under Contract No. 290-02-0022.) AHRQ Publication No. 05-E024-2. Rockville, MD Agency for Healthcare Research and Quality, July 2005.