Lectin Content of Beans: High vs Low Lectin Varieties
If you are familiar with the so-called Paleolithic diet, there's a good chance you have already heard of lectins. Lectins (not to be confused with the leptin) are proteins that occur in a wide range of plants, ranging from legumes like beans and peanuts to nightshade plants like tomatoes and potatoes. In the Paleo community, lectins have gotten a bad rap because some lectins can be extremely toxic when consumed in large enough amounts, and if you suffer from an autoimmune disease, even small amounts of certain types of lectins could be problematic. Raw legumes such as uncooked beans, peanuts and chickpeas, for example, contain toxic lectins which you will want to avoid.
The good news is that cooking destroys lectins in beans, provided that you cook them long enough and at a high temperature. In fact, a study published in the Journal of Agricultural and Food Chemistry in 2002 concluded that common edible beans that have been prepared and cooked properly are unlikely to cause lectin-related adverse effects in healthy people. But, some people in the Paleo community believe that even tiny amounts of bean lectins may cause health problems in susceptible individuals. If you are one of them, you may have wondered if the lectin content of beans varies depending on variety.
The short answer is yes, the amount of phytohemagglutinin, the presumed toxic lectin in beans, can vary significantly among bean varieties. Here's an example: According to a paper published by the U.S. Food and Drug Administration, raw red kidney beans contain from 20,000 to 70,000 hemagglutinating units (hau) of phytohemagglutinin (when fully cooked, their lectin content drops to 200 to 400 hau). White kidney beans, by contrast, contain only about one-third the amount of phytohemagglutinin the red variety contains, and broad beans contain even less, about 5% to 10% the amount that red kidney beans contain.
Another example: A study published in the Indian Journal of Agricultural Biochemistry found the lectin content of chickpeas to be in the range of 1160 to 1375 hau/g grain, which was almost twice as high as the lectin content of lentils (513 to 617 hau/g).
Chart: High vs Moderate vs Low Lectin Bean/Legume Varieties
To give you a rough idea of the lectin content of different beans, HealWithFood.org combed through existing research on the topic and put together a chart that groups some common legumes into different categories depending on their lectin content. Each bean/legume included in the chart is put into one of three categories—high, high/moderate, or moderate/low lectin content—based on how researchers have described the lectin content of the respective variety.
| Very High | High/Moderate | Moderate/Low |
|---|---|---|
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Sources:
1. G. Grant et al (1991). A survey of the nutritional and haemagglutination properties of several tropical seeds, Livestock Research for Rural Development, Volume 3, Number 3.
2. Bad Bug Book, 2nd edition. Foodborne Pathogenic Microorganisms and Natural Toxins Handbook. Food and Drug Administration.
3. G. Grant et al (1995). Consumption of diets containing raw soya beans (Glycine max), kidney beans (Phaseolus vulgaris), cowpeas (Vigna unguiculata) or lupin seeds (Lupinus angustifolius) by rats for up to 700 days: effects on body composition and organ weights. British Journal of Nutrition, 73(1):17-29.
4. A. Pusztai et al (1979). Nutritional evaluation of kidney beans (pxshaseolus vulgaris): Chemical composition, lectin content and nutritional value of selected cultivars. Journal of the Science of Food and Agriculture, Volume 30, Issue 9, pages 843-848.
Why You Should Use the Chart Only as a Rough Guide
Since the information in the chart above has been compiled from many different sources and those sources may differ in how they define high, moderate, and low lectin beans/legumes, you should use the chart only as a rough guide and do you own research. What's more, research suggests that the same bean or legume may contain varying amounts of lectins depending on when and where the plant was grown and how it was processed after harvesting. According to a study published in The American Journal of Clinical Nutrition, it is also possible that the lectin-related activities of a food may vary from one day to another.
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