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What are Antinutrients and Why Are They Bad?

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  Published on October 2nd, 2020
  Reading time: 4 minutes
  Last modified March 7th, 2023
Chickpeas contain antinutrients

Plant foods contain a range of nutrients and compounds that have health benefits, but they might also contain anti nutrients. Antinutrients are naturally occurring or synthetic plant compounds that interfere with the absorption of nutrients from your digestive system.

Antinutrients reduce your body’s ability to absorb essential nutrients. For most people, they aren’t a major concern. They might be an issue for those dealing with malnutrition, certain medical problems, and those who consume large amounts of legumes and grains. Grains and legumes are typically only consumed in small amounts on the keto diet due to the carb count.

On the other hand, some research shows antinutrients like phytates and tannins might have some beneficial health effects [1].

The antinutrients that have been most widely studied include:

1.   Phytate (phytic acid)

Phytates are primarily found in grains, seeds, and legumes. Phytates decrease the absorption of minerals from foods, such as iron, zinc, calcium, and magnesium [2].

2.   Tannins

Tannins are a class of antioxidant polyphenols, but they might impair the digestion of certain nutrients [3].

3.   Lectins

Lectins are present in all plant foods, particularly in legumes, seeds, and grains. Some lectins might inhibit nutrient absorption and be harmful in high amounts [4] [5].

4.   Calcium Oxalate

Calcium oxalate is the main form of calcium present in vegetables like spinach. Oxalic acid present in some plant-based foods may bind to calcium. The calcium bound to oxalate is poorly absorbed [6] [7].

5.   Protease Inhibitors

Protease inhibitors are found in many plants, particularly in grains, legumes, and seeds. Protease inhibitors inhibit digestive enzymes and interfere with protein digestion.

How Can You Decrease the Number of Antinutrients in Your Diet?

By sprouting, fermenting, boiling, or soaking, you can decrease the number of antinutrients present in foods. Combining some of these methods can substantially reduce antinutrients, in some cases, almost completely [8] [9].


You can soak beans and other legumes in water overnight to improve the nutritional value. Most antinutrients are found in the skin. Many antinutrients are also water-soluble, so they dissolve when you soak foods [10].

Soaking legumes has been found to reduce protease inhibitors, phytates, lectins, calcium oxalate, and tannins. A 12-hour soak decreased the phytate content of peas by up to 9% in one example [11].

In another study, soaking pigeon peas for 6-18 hours reduced lectins by 38-50%, protease inhibitors by 28-30%, and tannins by 13-25% [12].

Soaking some beans, such as soybeans, kidney beans, and faba beans, might be less effective at reducing certain antinutrients. You can also soak some leafy vegetables like spinach to reduce some of the calcium oxalates. Soaking is typically used along with other methods like sprouting, cooking, and fermenting [13] [14].


Sprouting refers to the life cycle of plants when they begin emerging from the seed (germination). This natural process increases the availability of the nutrients in legumes, grains, and seeds.

Sprouting typically takes a few days:

  • Rinse the seeds to remove all dirt, soil, and debris
  • Soak the seeds in cool water for 2-12 hours (soaking time depends on the type of seed)
  • Rinse them thoroughly in water and drain as much water as possible
  • Place the seeds in a sprouter or sprouting vessel away from direct sunlight.
  • Repeat rinsing and draining 2-4 times [15].

The changes that take place during sprouting degrades antinutrients like phytate and protease inhibitors. Sprouting can reduce phytate by 27-81% in different types of legumes and grains. There’s also a slight reduction in protease inhibitors and lectins during sprouting [16] [17].


Historically, fermentation has been used to preserve food. Fermentation is a natural process where microorganisms like beneficial bacteria and yeast start digesting the sugar and carbs in food.

Controlled fermentation is widely used in food production. For example, many food products are fermented, such as cheese, wine, and yogurt. Sourdough bread is one example of fermented food that effectively degrades antinutrients in grains [18] [19]. Fermentation effectively decreases lectins and phytates in various legumes and grains.


Using high heat and boiling your foods can degrade antinutrients like lectins and tannins [20] [21]. For example, calcium oxalate is reduced by 19-87% in boiled leafy green veggies. Baking and steaming aren’t quite as effective.

It’s also important to note that phytate is heat-resistant and doesn’t degrade as easily with boiling. Longer cooking time usually results in fewer antinutrients [22].

Do You Take Any Steps to Reduce Antinutrients in Your Diet?

Luckily on diets like the ketogenic diet, Mediterranean diet, or Paleo diet, you are less likely to consume grains, beans, and legumes, lowering your risk of consuming antinutrients. But, if/when you do consume these foods, are you taking any of the precautions mentioned (like boiling or sprouting)? Comment below and let us know your process!

Steph Green is a content writer specializing in and passionate about healthcare, wellness, and nutrition. Steph has worked with marketing agencies, written medical books for doctors like ‘Untangling the Web of Dysfunction,’ and her poetry book ‘Words that Might Mean Something.’ In 2016, after four years of struggling with her own health problems and painful autoimmune disease, Steph developed a life-changing and extensive knowledge of keto, nutrition, and natural medicine. She continues on her healing journey and enjoys helping others along the way.



Chung, K. T., Wong, T. Y., Wei, C. I., Huang, Y. W., & Lin, Y. (1998). Tannins and human health: A review. Critical Reviews in Food Science and Nutrition, 38(6), 421-464.


Schlemmer, U., Frolich, W., Prieto, R. M., & Grases, F. (2009). Phytate in foods and significance for humans: Food sources, intake, processing, bioavailability, protective role and analysis. Molecular Nutrition and Food Research.


Chung, K, T., Wei, C., & Johnson, M. G. (1998). Are tannins a double-edged sword in biology and health? Trends in Food Science and Technology, 9(4), 168-175.


Vasconcelos, I. M., & Oliveira, J. T. A. (2004). Antinutritional properties of plant lectins. Toxicon, 44(4), 385-403.


Nachbar, M. S., & Oppenheim, J. D. (1980). Lectins in the United States diet: A survey of lectins in commonly consumed foods and a review of the literature. American Journal of Clinical Nutrition, 33(11), 2338-2345.


Heaney, R. P., & Weaver, C. M. (1989). Oxalate: Effect on calcium absorbability. American Journal of Clinical Nutrition, 50(4), 830-832.


Heaney, R. P., Weaver, C. M., & Recker, R. R. (1988). Calcium absorbability from spinach. American Journal of Clinical Nutrition, 47(4), 707-709.


Zhou, J. R., & Erdman Jr, J. W. (1995). Phytic acid in health and disease. Critical Reviews in Food Science and Nutrition, 35(6), 495-508.


Santos-Buelga, C., & Scalbert, A. (2000). Proanthocyanidins and tannin-like compounds: Nature, occurrence, dietary intake, and effects on nutrition and health. Journal of the Science of Food and Agriculture.


Fernandes, A. C., Nishida, W., Proenca, R. P. D. (2010). Influence of soaking on the nutritional quality of common beans (Phaseolus vulgaris L.) cooked with or without the soaking water: A review. Journal of the Science of Food and Agriculture.


Bishnoi, S., Khetarpaul, N., & Yadav, R. K. (1994). Effect of domestic processing and cooking methods on phytic acid and polyphenol contents of pea cultivars (Pisum sativum). Plant Foods for Human Nutrition, 45(4), 381-388.


Savage, G. P., & Dubois, M. (2006). The effect of soaking and cooking on the oxalate content of taro leaves. International Journal of Food Science and Nutrition, 57(5-6), 376-381.


Singh, A. K., Rehal, J., Kaur, A., & Jyot, G. (2015). Enhancement of attributes of cereals by germination and fermentation: A review. Critical Reviews in Food Science and Nutrition, 55(11), 1575-1589.


Bau, H-M., Villaume, C., Nicolas, J-P., & Mejean, L. (1999). Effect of germination on chemical composition, biochemical constituents and antinutritional factors of soya bean (glycine max) seeds. Journal of the Science of Food and Agriculture.


Leenhardt, F., Levrat-Verny, M-A., Chanliaud, E., & Remesy, C. (2005). Moderate decrease of pH by sourdough fermentation is sufficient to reduce phytate content of whole wheat flour through endogenous phytase activity. Journal of Agriculture and Food Chemistry, 53(1), 98-102.


Lopez, H. W., Krespine, V., Guy, C., Messager, A., Demigne, C., & Remesy, C. (2001). Prolonged fermentation of whole wheat sourdough reduces phytate level and increases soluble magnesium. Journal of Agriculture and Food Chemistry, 49(5), 2657-2662.


Ur-Rehman, Z., & Shah, W. H. (2001). Tannin contents and protein digestibility of black grams (Vigna mungo) after soaking and cooking. Plant Foods in Human Nutrition.


Chai, W., & Liebman, M. (2005). Effect of different cooking methods on vegetable oxalate content. Journal of Agriculture and Food Chemistry, 53(8), 3027-3030.

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