(Part 3 of the Food Sensitivity Series)
Ever feel like your intestines have been pulled out, scrubbed, and hung out to dry? Eating large quantities of foods and herbs containing compounds called saponins (pronounced SAP-uh-nins) can cause this assault on your gastrointestinal (GI) system. Saponins derive their name from the Latin word for soap and represent a class of bio-active compounds called glycosides (GLEYE-kuh-sides). Not surprisingly, they froth up when shaken in water.
Although they are found in many of the same foods that contain lectins, saponins are not proteins, yet they can also lead to increased permeability of the intestinal lining, called “leaky gut.” The resulting gut irritation symptoms might range from mild discomfort with associated nausea to feeling extremely beat up inside with a side of vomiting or diarrhea.
These glycosides are found in plant tissues (leaves, stems, tubers, fruits, and/or seeds) and some marine animals like the sea cucumber and starfish. Saponins protect plants from herbivores and insects since they are bitter and astringent tasting. Humans can tolerate some amount of saponins, but consuming large amounts or combinations of saponin-containing foods and herbs can precipitate GI irritation. The triggering doses vary for each person.
Saponins occur in small amounts in many foods, but the greatest amounts are found in chickpeas, soybeans, alfalfa sprouts, peanuts, lentils, navy beans, kidney beans, peas, oats, quinoa, millet, amaranth, spinach, beet greens, tea leaves, asparagus, garlic, and Chinese yam. Many vegans use the canned chickpea fluids to make whipping toppings, taking advantage of the frothiness factor, but others may not tolerate This concoction.
Glycoalkaloid saponins are found in large quantities in unripe tomatoes and potatoes exposed to light which causes their skin to turn green. They are also found in smaller quantities in ripe tomatoes, eggplants, peppers, and other members of the nightshade family. This may explain in part why nightshade fruits are considered “inflammatory.”
Herbs such as licorice root, ginseng, fenugreek, and aloe vera are fairly rich glycoside sources. Some over-the-counter supplements and Chinese herb mixtures may contain saponin-containing plant parts which could cause gastrointestinal distress as the dose is increased. As was the case with lectins, some saponins have beneficial effects which have been utilized in both pharmaceutical and traditional medicines. These phytochemicals have been described as having cholesterol-binding effects, anti-cancer properties, as well as antimicrobial and antiparasitic qualities[1] to name a few.
Because of their foaming, stabilizing, and emulsifying qualities, both natural and synthetic saponins are used by the food industry as additives. Quillaja saponaria (or quillaia) extract is a natural agent that is listed as GRAS (generally recognized as safe) by the USDA; it may be found in some sodas and frozen dairy treats.[2] If an ultra-processed food bothers you and the label lists “quillaja extract,” “foaming agent,” “stabilizer,” or “emulsifier,” a saponin may be to blame.
For some, this may be an “aha” moment, and if you like these foods, here are some measures to try for reducing saponin levels.[3] Saponins are heat resistant but can be removed from legumes by discarding the water after each rinsing, soaking, and boiling step as well as by draining and rinsing canned beans. Fermentation of soybeans to yield tempeh reputedly lowers their saponin content. Soaking quinoa for about 20 minutes (or overnight) and then draining it before cooking may improve your tolerance of this high protein pseudo-grain. Avoid buying greenish potatoes from the grocery store and store potatoes in a cool dark place to prevent light from causing the skins to turn green, indicating increased content of the glycoalkaloid, solanine.[4] Since the skins contain the most glycosides, peel potatoes and cut out any green parts. Allow tomatoes to fully ripen on the counter before slicing. (Putting them in a bowl with bananas will accelerate this process.) Pickled and fried green tomatoes are traditional foods in the US, but neither preparation removes the saponins so eat them sparingly.
With foods, herbal medicines, supplements, and food additives, the dose determines whether you have ill effects. Combining many saponin-containing foods in a meal could produce additive effects. Keeping a food diary, taking care with ingredients in cooking, and reading labels all help to determine what components may be bothering you and which ones you might avoid before retrying them later in smaller amounts.
**Summary of Saponin-containing Foods**
Legumes: chickpeas (garbanzo beans), soybeans, peanuts, navy beans, broad beans, fava beans, kidney beans, peas, alfalfa sprouts, & lentils
Grains & Pseudo-grains: oats, quinoa, millet, & amaranth
Vegetables: spinach, beet greens, asparagus, Chinese yam (nagaimo), potatoes (esp. green parts), tomatoes (esp. unripe), eggplants, peppers
Herbs: garlic, tea leaves, licorice root, ginseng, fenugreek, aloe vera
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[1] Tessa Moses, Kalliope K. Papadopoulou, and Anne Osbourn, “Metabolic and Functional Diversity of Saponins, Biosynthetic Intermediates and Semi-Synthetic Derivatives,” Critical Reviews in Biochemistry and Molecular Biology 49, no. 6 (November 2014): 439–62, https://doi.org/10.3109/10409238.2014.953628.
[2] Yakindra Prasad Timilsena, Arissara Phosanam, and Regine Stockmann, “Perspectives on Saponins: Food Functionality and Applications,” International Journal of Molecular Sciences 24, no. 17 (August 31, 2023): 13538, https://doi.org/10.3390/ijms241713538.
[3] Kartik Sharma et al., “Saponins: A Concise Review on Food Related Aspects, Applications and Health Implications,” Food Chemistry Advances 2 (October 1, 2023): 100191, https://doi.org/10.1016/j.focha.2023.100191.
[4] “Solanine Poisoning – How Does It Happen?,” MSU Extension, accessed March 17, 2022, https://www.canr.msu.edu/news/solanine_poisoning_how_does_it_happen.
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