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Everything you need to know about lectins

Ask the Dietitan, Expert answers, General health, Nutrition

Everything you need to know about lectins

Is going lectin free (still) the new big thing?

This guest post is written by Moe Brandi who holds an MSc in Food Innovation and Health and specializes in bioactive components in foods that improve human health. Her work centers around natural ingredients and a strong belief that food can be healthy, delicious, and gratifying at the same time.

If you are familiar with the former heart-surgeon, Dr. Steven Gundry, you have probably heard about the “lectin-free diet” and his renown book “The Plant Paradox” (2017)

According to Dr. Gundry, plants are chemists of incredible ability: They have developed an array of defense and safety strategies to protect themselves against predators, including their content of plant-based proteins called lectins. These proteins were evolved to have an evolutionary purpose and humans were never intended to eat them, according to Gundry. He also claims that lectins are directly linked to weight gain by binding to insulin receptors and blocking the hormone from doing its action. Is insulin-dependent diabetes therefore potentially caused by lectins? Is it true that most plants want to make you ill? 

Below, we will answer some of these questions and give you an introduction to lectins, and what you need to know before including or excluding them from your diet. 

As with everything, and especially with food and dietary trends, we want you to stop for a second and listen to your body. You are unique! For some people, the FODMAP, ketogenic,  or lectin-light diet might work. This does not mean that these diets are necessarily right for you. Maybe you feel more in balance and better by just avoiding or decreasing your intake of nightshade vegetables. Maybe you just have to avoid raw tomatoes (cooking your tomatoes actually increases its anti-cancer compound, lycopene). Overall, one person’s tree nut allergy should not mean another person should avoid eating almonds.

That said, always consult your healthcare provider before starting on a new, restrictive diet. 

What are lectins?  

Lectins are carbohydrate-binding proteins with at least two carbohydrate binding sites, which also allows cross-linking between cells. The proteins select and bind to monosaccharides like glucose, galactose, mannose, and N-acetylglucosamine as well as oligosaccharides, composed of some of the mentioned monosaccharides. Thus, linking cells together by combining with sugars on their surfaces - just like how a key fits into a lock.

Lectins are known to promote cell growth and communication between cells - generally involved with cellular metabolism. 

 

What foods contain lectins?  

Lectin proteins are found all over the place in nature, from microorganisms to plant species and animals. They are especially found in a variety of plant based foods like legumes ( beans, lentils, peas, soy, seeds in general), peanuts, grains (like wheat and barley), nightshade vegetables (potatoes, eggplant, tomatoes, peppers), and fruits (ripe banana). 

To give an example, undercooked or raw kidney beans contain the lectin phytohemagglutinin, which is responsible for red kidney bean poisoning (according to Food and Drug administration, FDA, consuming just 4 raw kidney beans could cause symptoms like severe nausea, vomiting, and diarrhea). Another example of a type of lectin that most people know is gluten. 

 

Nutritional value of lectins

Lectins are not appraised for their nutritional value, but are mostly found in foods that do have a range of nutritional benefits, like dietary fibers and polyphenols (also known as plant defense compounds similar to that of lectins). Lectins are indigestible and resistant to gastric acid and digestive enzymes - they will stay intact through digestion. 

Actually, lectins may block the absorption of nutrients by binding to them and the cells lining our GI-tract, this is why they are commonly viewed as ‘anti-nutrients’. Ingesting lectins in excess amounts could therefore lead to digestive problems. 

Though, because lectins bind carbohydrates, they may slow down their digestion and lower the glycemic index, contributing to e.g. anti-diabetes effects of many legumes and other plant foods. As they are also found in plant based foods with cancer-fighting properties like tomato, beans, mushrooms, and bananas, some of these lectins are actually studied now as potential cancer therapies. 

 

Are lectins bad? 

Lectins are not necessarily bad, most of them are harmless (and indigestible), but others like ricin, produced in the seeds of the castor oil plant, can be fatal in even small amounts.

When it comes to disease, lectins have gotten a very bad reputation over the years, and “The Plant Paradox” goes so far as to say that lectins are the root of all disease. According to the book, going lectin free will improve not only your digestion, but also give you more energy (and brain power), less gas and bloating postprandial, better mood, and weight loss. 

Below is listed just a few viewpoints and research topics of lectins linked to disease:

  • Inflammation 
  • Obesity and diabetes (lectins may promote fat storage and act as ‘fake hormones’, blocking the normal action of your hormones like insulin)
  • Clustering in red blood cells
  • Higher risk of heart disorders 
  • Auto-immune diseases (e.g. multiple sclerosis, T1 diabetes)
  • Food intolerances and sensitivities (e.g. dairy, gluten, peanut, soy)
  • Disruption of the cellular wall in the GI-tract (leading to leaky gut and inflammation)
  • Digestive damage and gut bacteria imbalance   

     

    All these views and claims on lectins can seem scary, but evidence to date still does not support the exclusion of lectins from the diet outside of ‘condition-specific diets’. To repeat this, none of the claims on ‘lectins and disease’ or purported benefits of going completely lectin-free, are backed up by research. However, non-conclusive but interesting preclinical and in vivo studies do show a potential connection between lectins and inflammation. Lectins may trigger an autoimmune response, like type 1 diabetes, when bound to cells for a long period of time. Further research is needed.

    There are also ways to reduce, neutralize or eliminate the lectins from specific lectin-rich foods if you are dealing a lot with digestive problems, food intolerances, or notice any side effects after eating lectin-rich foods. It could be that you have a sensitivity to certain components of those foods. Consider reducing the amount of them, avoiding them altogether, or cooking them adequately instead of eating them raw (this is often the case with tomatoes). 

     

    How to reduce lectins 

    Introducing daily practices like soaking grains and legumes will not only reduce potential lectin side effects, but also release nutrients for better absorption. Adverse reactions to certain kinds of toxic lectins are avoided by adequate cooking. 

    Furthermore, this is our list of food practices that will reduce or deactivate lectins in your food prior to eating: 

    1. Soaking and sprouting for ~ 12h (legumes like all types of beans, lentils, oats, barley, wheat grain varieties). Soaking or sprouting foods in the legume family will also release nutrients and overall make this food group easier to digest.
    2. Tip: Add a pinch of baking soda to the soaking water (and renew the water as often as possible) - this may help neutralize and reduce the lectins further.
    3. Cooking and pressure cooking (legumes and certain vegetables)
    4. Deseeding (e.g. tomatoes and cucumbers)
    5. Peeling (e.g. tomatoes and cucumbers). Tip for peeling tomatoes: Add them to boiling hot water for 30 sec followed by an ice bath (add ice cubes to a bowl with cold water). Now, the peel is easily removed by hand. 
    6. Fermenting
    7. Eating refined (choose white grains over whole grains). Tip for choice of bread: Buy or make your own sourdough bread with white flour instead of whole wheat bread fermented with commercial yeast.

     

    Be aware that some of the above practices may reduce the overall nutritional value and fiber content of the foods (like removing the peel and choosing white over whole grains). Indeed, having a fiber-rich diet and eating whole grains will not only stimulate your gut bacteria and give you regular bowel movements, but studies also show that eating whole grains are associated with reduced risk of heart disease, diabetes, and various cancers. Therefore, we recommend that you begin with introducing practices like soaking and sprouting your grains (e.g. prepare your oat porridge the night before so the oats can soak in water overnight) instead of avoiding them all together. If you have been advised by your healthcare provider to decrease the amount of lectins in your diet, you should balance your meals and choose white rice some days, brown rice other days, etc. 

     

    Examples of a lectin free diet 

    If you are curious about trying a lectin friendly diet, we have added our tips here below. Feel free to make your own moderations, depending on your food tolerability and personal goals.   

    What you can eat: 

      • Leafy greens and the following vegetables: Broccoli, brussel sprouts, cauliflower, bok choy (can replace cucumber), cabbage, collards, sauerkraut (fermented), kimchi (fermented), celery, carrots, beets, sweet potato, radishes, heart of palm, okra, asparagus, sea vegetables, garlic/onions, mushrooms, and avocado. 
      • Olive oil  (extra virgin, cold pressed)
      • Only eat fruits and berries when in season 
      • Fermented soy products are allowed like miso
      • Pasture-raised meats and eggs 
      • Mozzarella and parmesan cheese sourced responsibly
      • Monk fruit sweetener

         

        What you should reduce:

          • Whole wheat, brown rice, barley
          • Beans and lentils 
          • Nightshade vegetables (potatoes, eggplant, tomatoes, peppers)
          • Fruits

             

            What you should avoid all together: 

              • Soy (and edamame beans)
              • Corn
              • Dairy (avoid regular A1 cows milk - instead, look for other sources like A2 milk, goat or sheep milk)
              • Peanut

                 

                Some additional tips making it easier to go lectin friendly: 

                  • We have talked a lot about the difference between ripe (yellow) and unripe (green) bananas. We recommend you to eat unripe/green bananas or powder in order to increase the amount of the prebiotic resistant starch. If you are on a lectin friendly diet, you are also allowed to enjoy green bananas, but not ripe bananas as they contain lectins in addition to the high amount of sugar. 
                  • Sorghum is a great source of fiber (resistant starch) and low in lectins in comparison to barley, brown rice, quinoa, and whole wheat. 
                  • Avoid peanuts and peanut butter if you are on a lectin friendly diet. Go instead after blanched almond butter (almonds without peel), hazelnuts, macadamia nuts, pecans, pistachios, and walnuts. If you want to consume the nuts as butters, go for butters with no added sugar or vegetable oils like sunflower oil or palm oil (this is mentioned on the label). 
                  • If going lectin friendly, always reduce the amount of lectins in certain foods by soaking and cooking them adequately. 

                     

                    Our recommendations

                    We don’t want to warn you against eating plant-based foods rich in lectins, including some of the healthiest foods you can find, when we are dealing with so many chronic diseases linked to heavily processed foods and low fiber/low nutrient foods. Generally, lectins are beneficial and neutral in small doses.

                    When looking at other plant bioactive components like antioxidant polyphenols/phytonutrients, these are also considered mild stressors for our body when ingested in ‘normal’ amounts throughout the day (i.e. hormesis). Our body’s adaptation to this mild stress is actually good for us (like exercising) - so small and manageable doses of toxins can make you stronger, while too large doses will not. 

                    If you are on a vegetarian or plant-based diet, it will be difficult to obtain a healthy amount of daily proteins if avoiding beans, lentils, peas, and seeds. Furthermore, choosing a restrictive diet like the lectin free diet could lead to nutritional deficiencies if you are not a nutritional expert.  Going lectin-friendly can also be a costly (and restrictive) affair if you are consuming meat and dairy everyday (pasture-raised and A2 milk are expensive). 

                    However, some population groups may have been advised by their healthcare provider to reduce or avoid their intake of lectins. Especially, people with allergies to lectin-containing foods - grains/cereals, dairy, peanut, and soybean from the legume family are today the most commonly associated with digestive disorders, intolerances, and sensitivities. Though, for most people, a diet based around whole plant foods is a great way to optimize health and to fight disease.

                    As a final note, leafy greens and olive oil combined with seasonal fruits, vegetables, and beans (a daily dose) have been enjoyed by the longest-lived people on the planet and are defined as longevity foods. These people ate 4 times more beans than Americans do on average. So, beans cannot be that harmful after all. 

                     

                    References

                    Bad Bug Book (FDA)

                    Blue Zones

                    Dr. D’Adamo (blood type diet)

                    Dr. Gundry homepage 

                    Food Revolution Network

                    Gundry MD blog

                    International Journal of Molecular Science (Report 2017)

                    Journal of Immunology 

                    Medical News Today

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