What Soy Foods Can Fit into the Low FODMAP Diet

The FODMAP diet, which stands for fermentable oligosaccharides, disaccharides, monosaccharides, and polyols—all short-chain carbohydrates—may help with managing symptoms associated with irritable bowel syndrome (IBS). Learn more about this diet, how certain clients can benefit from it, and which soy foods fit into it.

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What Are FODMAP Carbohydrates?

Saccharides can be broken into different types of carbohydrates depending on their chain length. FODMAPs are small-chain carbohydrates that are difficult to absorb in the small intestine. These can trigger digestive distress in those who experience visceral hypersensitivity (a sensitive gut), which is frequently observed in irritable bowel syndrome (IBS)—a chronic GI condition that causes bloating, abdominal pain, and changes in bowel habits. It is important to note that foods containing FODMAPs can be healthy, generally do not cause painful gastrointestinal (GI) symptoms in those with a healthy gut, and should be enjoyed liberally by those who can tolerate them.

The Low FODMAP Diet: Who Might Benefit?

Food intolerance is common, impacting about 15-20% of the global population.¹ A diet low in FODMAP carbohydrates has shown great promise for symptom management for those living with IBS. IBS impacts up to 20% of Americans.² Food-related symptoms are common in IBS. One survey of nearly 200 patients with IBS revealed that up to 84% reported symptoms related to at least one of the food items surveyed, resulting in digestive distress.³ Similar to IBS, people with celiac disease and inflammatory bowel disease may also experience food related GI symptoms. Research has shown that reducing FODMAP carbohydrates may benefit symptom control in clients living with these conditions.^4,5

The Origins of the Low FODMAP Diet

Despite patient complaints of food-related GI symptoms in IBS, for years, the medical community had very little to offer regarding nutritional intervention to calm gut pain. There was little science to support the use of diet for therapeutic benefit in IBS until a research group at Monash University in Melbourne, Australia, introduced the novel low FODMAP diet in 2005. With growing interest and numerous randomized controlled trials to date, the low FODMAP diet has been shown to be an effective therapy, managing GI symptoms with 40-50% of IBS patients reporting adequate relief.^6,7

The low FODMAP diet is a 3-phase nutritional approach. Despite its high effectiveness, it is a nuanced diet with a high level of dietary modification that should involve professional oversight for the best compliance and improved success rate.⁸

How Do FODMAPs Cause GI Distress in IBS?

IBS is a digestive condition characterized by a hypersensitive intestine. Poorly absorbed FODMAP carbohydrates can produce varying degrees of osmotic effects in the gut by pulling water into the intestinal tract. This is due to the small size of FODMAP carbohydrates, which contribute to luminal distention and can trigger GI symptoms in patients with IBS.
Moreover, gut microbes feast on these unabsorbed carbohydrates, producing gas, short-chain fatty acids, and various metabolites. The stretching of the intestinal tract via the extra water and gas in the gut results in cramping and gut symptoms. Gut microbe-derived metabolites from FODMAP fermentation may also play a role in triggering symptoms, but this area needs to be studied further.⁹

How Soy-Based Foods Fit into a Low FODMAP Diet

There are many soy-based foods that are suitable for the low FODMAP diet, such as firm tofu, soy cheese, plain tempeh, edamame, soybean oil, soy sauce, miso, and some soy milk.¹⁰

Food processing, fermentation, and plant maturity can impact soy foods' FODMAP content. For examples of low and high FODMAP soy foods, see Table 1.

Table 1: Low and High FODMAP Soy-based Foods

Low FODMAP	High FODMAP
• Soy cheese • Tempeh (plain) • Firm tofu • Soymilk (made with soy protein) • Soybean oil • Soy sauce • Miso • Edamame	• Soy yogurt • Silken tofu • Textured vegetable protein • Soymilk (made with the whole soybean)

Unknown FODMAP Status: Natto, soynuts, soynut butter

The FODMAP Contents of Different Soy Foods

Because FODMAPs are water-soluble carbohydrates, draining off the liquid before cooking and eating, as you would with firm tofu, reduces the FODMAP content. Silken tofu, which has a higher water content, retains more FODMAPs. That’s because the liquid contains water-soluble oligosaccharides from the soybeans. In addition, the fermentation process used to make tempeh reduces its FODMAP content.¹¹ Natto, a fermented soybean dish, has yet to be tested for FODMAPs, and soy yogurt has been tested as high FODMAP.

Products that utilize soy protein versus the whole soybean are also lower in FODMAP carbohydrates. For example, soy milk made with whole soybean is high in FODMAPs, while soy milk made with isolated soy protein is low in FODMAPs.^10,12 Isolated soy protein may be lower in FODMAPs if only the protein component is present (i.e., there is no residual fiber that may contain oligosaccharides in the product). Still, this ingredient has yet to be formally tested.

Textured vegetable soy protein is high in FODMAPs.¹⁰ Soy nuts and soy nut butter contain the whole mature soybean and are likely high in FODMAPs. As previously mentioned, the maturity of a plant may also play a role in the FODMAP content of the food. For example, edamame has fewer FODMAPs than mature soybeans.

Consuming an alpha-galactosidase enzyme supplement with 300 GALU (galactosides units) and foods such as soybeans with high amounts of galactooligosaccharides has been shown to mitigate IBS symptoms.¹³ This over-the-counter supplement may offer another way for clients with IBS to expand their soy intake, but it should be done under the supervision of a healthcare provider.

Summary

The low FODMAP diet is a 3-phase, evidence-based nutritional intervention utilized for IBS symptom management. Many soy-based foods are low in FODMAPs and suitable for consumption during the elimination phase of the diet. As a client goes through the reintroduction and personalization phases to identify their personal triggers, more soy foods may be incorporated as tolerated.

FODMAP intolerance varies per person, and the goal of the diet is to provide as much variety as possible to enhance food-related quality of life and overall health while managing GI distress in clients. The oligosaccharides component of soybeans offers prebiotics (food for beneficial probiotic microbes in the gut), which may positively impact the individual’s gut microbiome and health. Alpha galactosidase enzyme supplements taken with a soy-rich meal may offer improved tolerance to high FODMAP soy foods in clients with IBS.

REFERENCES

1. Lomer MC. Review article: the aetiology, diagnosis, mechanisms and clinical evidence for food intolerance. Aliment Pharmacol Ther. 2015;41(3):262-275. doi:10.1111/apt.13041

2. Canavan C, West J, Card T. The epidemiology of irritable bowel syndrome. Clin Epidemiol. 2014;6:71-80. Published 2014 Feb 4. doi:10.2147/CLEP.S40245

3. Bohn, et al. Self-reported food-related gastrointestinal symptoms in IBS are common and associated with more severe symptoms and reduced quality of life. Am J Gastroenterol. 2013;108:634-41

4. Cox SR, et al. Effects of Low FODMAP Diet on Symptoms, Fecal Microbiome, and Markers of Inflammation in Patients With Quiescent Inflammatory Bowel Disease in a Randomized Trial. Gastroenterology. 2020;158(1):176-188.e7. doi:10.1053/j.gastro.2019.09.024

5. Roncoroni L, et al. A Low FODMAP Gluten-Free Diet Improves Functional Gastrointestinal Disorders and Overall Mental Health of Celiac Disease Patients: A Randomized Controlled Trial [published correction appears in Nutrients. 2019 Mar 06;11(3):]. Nutrients. 2018;10(8):1023. Published 2018 Aug 4. doi:10.3390/nu10081023

6. Eswaran S, et al. A randomized controlled trial comparing the low FODMAP diet vs. modified NICE guidelines in US adults with IBS-D. Am J Gastroenterol. 2016;111:1824- 1832

7. Halmos EP, et al. A diet low in FODMAPs reduces symptoms of irritable bowel
syndrome. Gastroenterology. 2014;146(1):67-75.e5. doi:10.1053/j.gastro.2013.09.046

8. Tuck C, et al. Implementation of the low FODMAP diet in functional gastrointestinal symptoms: A real-world experience. Neurogastroenterol Motil. 2020;32(1):e13730. doi:10.1111/nmo.13730

9. McIntosh K, et al. FODMAPs alter symptoms and the metabolome of patients with IBS: a randomized controlled trial [published correction appears in Gut. 2019 Jul;68(7):1342]. Gut. 2017;66(7):1241-1251. doi:10.1136/gutjnl-2015-311339

10. Tuck C, et al. Fermentable short chain carbohydrate (FODMAP) content of common plant-based foods and processed foods suitable for vegetarian- and vegan-based eating patterns. J Hum Nutr Diet. 2018; 31:422–435 https://doi.org/10.1111/jhn.12546

11. McNamara L. Food processing and FODMAPs - what you need to know. Food processing and FODMAPs - A blog by Monash FODMAP | The experts in IBS - Monash Fodmap. https://www.monashfodmap.com/blog/food-processing-and-fodmaps-what-you/. Published February 7, 2017. Accessed June 27, 2020.

12. Taylor L. Eating vegan on a low FODMAP diet. A blog by Monash FODMAP | The experts in IBS - Monash Fodmap. https://www.monashfodmap.com/blog/eating-vegan-on-low-fodmap-diet/. Published November 25, 2014. Accessed June 20, 2020.

13. Tuck C, et al. Increasing symptoms in irritable bowel symptoms with ingestion of galactooligosaccharides are mitigated by α-galactosidase treatment. Am J Gastroenterol. 2018;113(1):124-134. doi:10.1038/ajg.2017.245