What Exactly Are Lectins? The Best and Worst Lectin Sources
You may have heard of gluten — and the dietary problems it causes — but have you heard of lectin? Known as an “antinutrient,” lectin is a type of plant-based protein commonly found in seeds, grains, legumes, and tubers, like potatoes. As an antinutrient, lectins may prevent your body from absorbing essential vitamins and minerals — but that's not all.
Research indicates that lectins may put certain people at risk for systemic inflammation, digestion problems, increased fat storage, and even autoimmune conditions, such as celiac disease and Crohn's disease.[1, 2, 3]
Although extensive research exists on the harmful effects of lectins, the jury is still out. Some experts say concerns about lectins are overstated since we cook many lectin-containing foods.
So what's the verdict? Are lectins bad for you? Let's dig into the research.
What Are Lectins?
Lectins are a broad class of protein found abundantly in plants. Lectins protect plants against microorganisms, insect pests, and animals that may eat them.
To the scientifically minded, they are “glycoproteins that bind carbohydrates and agglutinate cells.” Agglutinate means to clump; known as “sticky proteins,” lectins cause cells — including red blood cells, gut mucosal cells, and even probiotic bacteria — to clump together.
Definition: Lectins are proteins that protect plants against harm!
Rather than being digested and broken down, lectins survive the mammalian digestive system; this allows things like seeds to pass through a mammal's gut and still germinate. Lectins are particularly high in seeds.
However, to people, this may lead to gastrointestinal distress. Because we do not digest them, our bodies see them as foreign objects and produce antibodies to “attack” them; in other words, they trigger an immune system reaction.[6, 7]
Are Lectins Bad for You?
Research strongly suggests that consuming high amounts of lectins can cause health problems in some people who have a genetic sensitivity to them. The problem is that most people do not know their genetic makeup — only that they experience health concerns.
After you eat lectins, they bind to cell membranes, particularly those lining the digestive tract — called gut epithelial or gut mucosal cells.[1, 3] This binding can cause gut cells to die or lose function; lectins can also clump gut microbes together, disrupting an otherwise healthy gut biota.
Not all lectins are bad, but most people in the Western world eat too many of the problematic high-lectin foods — particularly grains and beans and even tomatoes.
If you regularly experience inflammation, disease, or gastrointestinal distress, try eliminating lectins and see if it helps. If you already have damaged gut mucosa, cutting out lectins will not make anything heal overnight, and you may not see immediate results from eliminating them. Your body may need time to heal.
If you are considering avoiding or minimizing lectins in your diet, here are the top science-based reasons.
1. Lectins Are Antinutrients
Did you know lectins can block the absorption of essential minerals?
Scientists refer to lectins as “antinutrients” — compounds that interfere with the body's ability to digest and use other nutrients. Lectins, in particular, block absorption of calcium, iron, phosphorus, and zinc — essential minerals you need.
If you eat lectin-rich beans along with other foods containing zinc or iron — or with your daily multivitamin — your gut may not absorb the minerals properly. Knowing this, you can consume these minerals or your multivitamin during a meal that does not contain lectins.
2. Lectins May Cause Inflammation
Animal studies show that lectins cause redness and swelling in the body by activating pro-inflammatory pathways, which affect immune function.[3, 4] They can cause the body to create antibodies as if lectin was a foreign invader, like a virus.
Your body responds to lectins like it does a virus!
Inflammation caused by consuming too many lectins may lead to autoimmune diseases such as rheumatoid arthritis and celiac disease — particularly in individuals with dysfunctional digestive enzymes. Long-term body inflammation increases your risk of heart disease and cancer.
Lectins also may stimulate a series of biochemical reactions that affect the pancreas and islet cells, which make the body vulnerable to an autoimmune attack, as well as diabetes. Gluten actually contains lectin, so people with gluten-sensitivity are especially advised to eliminate or minimize lectin intake.
3. Lectins May Permeate the Gut Barrier
When you consume lectins, they can damage the intestinal wall or epithelium.[6, 10, 11] While a healthy gut can repair itself from small amounts of damage, consuming high quantities of lectins could eventually lead to a leaky gut.[10, 11]
High amounts of lectins have the power to damage your intestinal wall. Ouch!
A healthy gut keeps partially digested food and microbiota in, only permitting nutrients to flow out as needed.
4. Raw Lectins May Be Toxic
Consuming undercooked or raw legumes may be toxic.[4, 6] When a hospital served red kidney beans for a “healthy eating day,” several people experienced severe vomiting and diarrhea. No pathogens were found in the beans, yet they contained particularly high levels of phytohaemagglutinin — a lectin that has caused other cases of “food poisoning.”
Side note: Because of the high toxicity of raw beans, never let young children play with them since they may swallow them.
Watch out! Undercooked or raw legumes can be toxic.
Cooking beans in a pressure cooker at a high temperature, or boiling them on the stove for at least 10 minutes, should denature lectins, making beans safer to eat.
5. Lectins May Cause Digestive Distress
Lectins clump (or agglutinate) cells, including helpful microbes as well as gut mucosal cells; this agglutination can cause gastrointestinal distress.[1, 5] As with gluten, not everyone responds the same way to lectin, and not everyone will experience side effects from eating the same foods.
Lectins may cause immediate symptoms in some people — typically GI symptoms like diarrhea, bloating, gas, or constipation. But in other people, lectins may silently damage your gut and body systems without you realizing it.
Foods High in Lectins
About 30 percent of the foods we eat contain lectins. Although some high-lectin foods also contain antioxidants, nutrients, and fiber, and may even provide benefits in small amounts, some nutritional experts advise you to avoid high-lectin foods or to limit your overall intake.
Did you know that 30% of the food we eat contains lectins?
According to Cornell University, the amount of lectins in plant foods — and their “agglutinating” properties — can vary from day to day and from store to store, so you may never know when you'll end up with a batch of beans with a too-high amount.
If you have digestion problems, like constipation or diarrhea, you might consider cutting out lectins for a while and see if your digestion improves.
The following foods are sources that are particularly high in lectins:
- Red kidney beans
- Navy beans
- Chickpeas (garbanzo beans)
- Soybeans and soy products
- Black beans
- Lima beans
- Black-eyed peas (cowpeas)
- Wheat and other grains
- White potatoes
- Nightshade vegetables including tomatoes, eggplant, peppers
Popular Low-Lectin Foods
If you worry about your consumption of lectins, there are plenty of healthy foods low in lectins to choose from. None of these foods is better than the others. Aim to eat a variety of these foods. Eating a diverse mix of whole, natural foods helps you consume a variety of nutrients for optimal health.
- Brussels sprouts
- Dark leafy greens
- Sweet potatoes
- Olive oil
- Citrus fruit
Should You Try a Lectin-Free Diet?
Choosing to avoid food that's high in lectin is a personal choice. Dr. Steven Gundry popularized the lectin-free diet with his book, “The Plant Paradox.” If consuming foods such as beans and grains causes you digestive problems, such as bloating or stomach discomfort, eliminating them from your diet may alleviate these symptoms.
If you are experiencing digestive issues from beans or grains, a lectin-free diet may help to alleviate your symptoms.
A lectin-free diet in and of itself likely will not cause weight loss, but eliminating the processed grain products that plague the Standard American Diet (nicknamed “SAD”) — and happen to have high lectin content — could help you shed pounds.
If you cut out foods with lectins, you may notice a quick change, or you may see no changes in your body. However, keep in mind that some benefits may work quietly inside your cells and tissues.
If you want to know whether you have a genetic susceptibility to lectins, you can also order a DNA kit online that will sequence your genes and reveal certain health conditions.
Other Natural Ways to Reduce Lectin Intake
If you choose to cut back on your intake of lectins, eliminating high-lectin foods isn't your only option. Below are the best ways to reduce lectins in these otherwise healthy foods so you can get the benefit of their nutrients — without the antinutrients.
Properly cooking foods reduces lectin levels, but they are surprisingly resistant to temperature. One study found moist heat more effectively denatures lectin protein than dry heat, though commercial roasting of nuts was enough to break down the lectins 100 percent.
Research has found that cooking decreases antinutritional compounds in chickpeas (although they did not look specifically at lectins).
Some studies have suggested that conventional home cooking may not break down lectins since they are very heat-stable; moist or dry heating at just 70 degrees C (158 degrees F) did nothing to the lectins in one study. When cooking beans at over 100 degrees C (212 F), it only took 10 minutes to break down lectins, at 95 degrees C (203 F) it took one hour.
In other words, you need to cook lectin-containing foods at a high enough temperature to eliminate them.
You might want to eat more fermented foods! Fermented foods made from beans have 95% less lectin content!
Fermentation also reduces the lectin content. One study found that fermenting lectins for 72 to 96 hours resulted in almost complete elimination of lectins. Fermented foods include kimchi (fermented cabbage), sauerkraut, and natto. Another study found fermenting foods made from beans reduced their lectin content up to 95 percent.
Did you know soaking legumes and grains deactivates 50% of the lectins?
Adding sodium bicarbonate (baking soda) to the water and soaking for 16 hours reduced levels of antinutrients in cowpeas in a study. If you cook beans, always soak them overnight, dump the soaking water, and then boil them in fresh water to reduce the lectin content.
You can go a step further by sprouting beans and grains, which may reduce the lectins in chickpeas and other legumes substantially. Germinating beans for 42 hours at 77 degrees F decreased lectins by almost 59 percent in one study.
Points to Remember
You may experience nausea, diarrhea, or other digestive symptoms from consuming lectin-containing foods, without realizing the culprit. Lectins are carbohydrate-binding proteins found in many plant foods such as beans, legumes, grains, dairy, and some vegetables. The more lectins in a particular food, the fewer sugars and starches are absorbed by your body.
Lectins are called “antinutrients” because consuming high quantities of lectin foods can prevent your body from absorbing other nutrients, particularly calcium, iron, phosphorus, and zinc.
Several studies on both humans and animals have found that lectins cause inflammation and digestive problems and may even contribute to autoimmune disease.
If you wish to reduce your consumption of lectins, cooking, soaking, sprouting, and fermenting beans, legumes, and grains will lower the level of lectins in those foods.
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