What You Need to Know About Lectin Proteins

What do beans, grains, nuts, tomatoes, eggplant, and peppers have in common? They have been wrongfully accused of being dangerous because they contain lectin proteins. So say advocates of the Paleo diet websites and books loaded with misinformation. All of which can confuse and harm people who are already eating an insufficient amount of plant foods. What is harmful to our health is promoting this twisted information which has led to many people being afraid to eat health-promoting foods like beans and tomatoes.

Unfortunately, nutritional misinformation abounds and the consumption of health fortifying nutrient-rich plant foods in our society is dangerously low. The Centers for Disease Control and Prevention (CDC) has stated that 75% of healthcare spending goes to treating chronic diseases, most of which are preventable and diet-related. 1 .

To say lectins are “disease-causing” and that people need to avoid beans, vegetables and nuts in order to get healthy and lose weight, has been thoroughly disproven by the thousands of studies documenting the health and longevity benefits of these foods. . 

The real story - what lectins do in our body

Lectins are proteins that bind carbohydrates. There are many different lectins, which have different functions because they bind to different carbohydrates. Lectins are not only present in plant foods; they are ubiquitous in nature – in plants, animals, and microorganisms.2

The main function of lectins in animals is to facilitate cell-cell contact – lectins on one cell recognize and bind to surface carbohydrates on another cell.  In plants, the function of lectins is less clear but some lectins are thought to be plant defense proteins, to protect against pathogens and insects. 3 This is similar to other phytochemicals; flavonoids, for example, also serve as natural defenses in plants. 4

Potential benefits of plant food lectins

Plant lectins bind carbohydrates during digestion, slowing or preventing their breakdown, and thereby reducing the glycemic effects of the food. 5  This action of lectins is most likely a contributing factor to the pro-weight loss and anti-diabetes effects of beans and other plant foods. Beans are rich in fiber and anti-cancer phytochemicals and demonstrate a powerful association with lower rates of colorectal, prostate, and breast cancers.6-8 

A lectin in common mushrooms has been found to inhibit proliferation of cancer cells in vitro.9,10   Mushrooms are another food offering powerful protection against cancer. ,11,12  And that’s not the only one: similar results have been found for lectins from fava beans, soybeans, bananas, buckwheat, jackfruit, and wheat.13-19 Some of these lectins are being investigated as potential cancer therapies.20,21 Certain plant food lectins may also help prevent cancer development by blocking the actions of angiogenesis-promoting lectins on human cells.20

Do lectins pose any dangers?

There is one lectin known to cause temporary gastrointestinal distress in humans called phytohemagglutinin; it is found in raw beans, red kidney beans in particular. However, it is easily avoided. This lectin is inactivated by cooking. If you use dry beans, take the necessary precaution of making sure they are thoroughly cooked – don’t eat undercooked beans. 

Special cases of sensitivity to certain lectins

Some food allergies are allergies to a lectin specific to that food. Also, bacterial infections, inflammatory bowel disease (IBD), colon cancer, or autoimmune illnesses may alter intestinal cells in a way that makes usually harmless food lectins problematic. For example, wheat may be problematic for rheumatoid arthritis and peanuts for IBD and colon cancer. However, carbohydrates from dietary fiber could potentially block or reduce these harms.22,23 It is likely there are individuals who should avoid a specific food because of their individual response to a lectin in that food. But this does not mean that lectins are harmful for the general population. 

Keep eating beans and tomatoes – they have huge health benefits

People who regularly eat beans have greater intakes of minerals and fiber, have lower blood pressure, and are less likely to be overweight than people that don’t consume beans.24 The consumption of beans is linked to lifespan enhancement, lower rates of cardiovascular disease, lower risk of colorectal and several other cancers.25-32

Tomatoes are the major source of the carotenoid lycopene, a strong antioxidant that helps protect the skin from UV damage. In addition, tomatoes have a number of cardiovascular system benefits including making LDL cholesterol more resistant to oxidation.36-38 Higher blood lycopene is associated with a lower risk of heart attack and stroke, and low blood lycopene are associated with a greater risk of premature death.39-43

Beans, vegetables, mushrooms, nuts and seeds are high-nutrient, fiber-rich foods that are consistently associated with beneficial health outcomes and a longer life.  The hypothesis that these foods are harmful due to the negative effect of certain plant lectins is without scientific merit and not supported by the preponderance of evidence from nutritional research studies.


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6/4/2019 7:00:00 AM
Joel Fuhrman, M.D.
Joel Fuhrman, M.D. is a family physician, New York Times best-selling author and nutritional researcher who specializes in preventing and reversing disease through nutritional and natural methods. Dr. Fuhrman is an internationally recognized expert on nutrition and natural healing, and has appeared on hundreds of radio a...
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