Understanding Lectins in Your Diet - Ask a Nutritionist

April 18, 2024

What are lectins and nightshades, and why have they become such a buzzword in nutrition circles, lately? This episode, hosted by Britni Vincent RD, LD, explains what these are, how they affect your health, and what foods have them.

Join Britni for expert advice to help you make informed dietary choices about consuming nightshades and foods with lectins. If you are just learning about lectins or want to learn a bit more...don't miss this episode!

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BRITNI: Welcome to Dishing Up Nutrition's “Ask a Nutritionist” podcast brought to you by Nutritional Weight and Wellness. I am Britni Vincent, a Registered and Licensed Dietitian. And we at Nutritional Weight and Wellness are thrilled to be celebrating 20 years on air discussing the connection between what you eat and how you feel while sharing practical real life solutions for healthier living through balanced nutrition.

I just want to say thank you so much for your support and listenership throughout the years and I want to get started on today's topic. I will be answering a nutrition question that we've received from one of our Dishing Up Nutrition listeners today. And the question is, “Can you address lectins and nightshades? Also, what are your thoughts on legumes causing inflammation? Should we be consuming these foods or avoiding them?”

I want to first start by saying this is not a straightforward answer and there are a lot of variabilities that come into play here. And I know that lectins have been a huge buzzword in the nutrition world for the last several years. And I don't think a lot of people actually understand what lectins are.

What are lectins?

So I want to first start by giving some background information. So lectins are a large class of carbohydrate binding proteins found in animals, humans and plants. And I think the role of lectins in plants is really what pertains to this person's question.

In plants, lectins act as a natural defense mechanism and are important for their survival. Lectins help to prevent insects and other animals from eating them. They may taste bitter and in some cases even be poisonous. And plant lectins are found in legumes, grains, nuts, fruits and vegetables. Some of the foods that contain the highest amounts of lectins are legumes, grains, and nightshades.

So nightshades and legumes were specifically called out on this question. So I'm going to address them more later in this episode. And it is important to note that there are different types of lectins found in these foods. And not all of them affect you in the same way.

Are consuming lectins recommended?

And there have been some claims the last several years that everybody should avoid lectins. And if you avoid them, then your health is going to improve. I do not agree with that statement at all. And the research really doesn't support that either. There may be some people that react to lectins, but I think complete avoidance for most people just really isn't necessary. And by avoiding them unnecessarily, you're missing out on some great tasting food and also some nutrient rich foods as well.

I am going to touch on that later when it might be worth exploring an elimination of some of these foods that do have high lectins. I want to talk about why lectins might be problematic. What's the concern here? So they have the potential to, and I want to really highlight the word potential because they're not going to cause these reactions in every person.

So they have the potential to be difficult to digest, may contribute to leaky gut, which you might have heard us talk about on previous episodes, but leaky gut is when little holes develop in the lining of your intestinal tract. So food, toxins, pathogens can escape from your intestinal tract into your bloodstream. So that's what leaky gut is.

Lectins may stimulate the immune system, which then increases inflammation. And for those that have autoimmune conditions, this may mean that lectins increase your autoimmune response. Certain lectins can prevent your body from absorbing other substances that have nutritional value. And in some cases, high amounts of lectins may cause nausea, vomiting, bloating, and diarrhea.

What does the research say? Many of the research studies that have been done on lectins, they've been done on animals and are not well applied to humans. And some of the studies include a much larger amount of lectins than what the majority of humans with a varied diet would ever consume. So again, not applicable.

And studies have used raw lectin containing foods, such as raw beans. And I don't think anybody eats raw beans that, that I'm aware of, so that research really does not apply because cooking beans does reduce lectins.

Do lectins have benefits?

There is actually some research suggesting that lectins may have some benefits. They might be antibacterial, antifungal, and antiviral. Lectins may also have the potential to improve blood sugar and insulin levels. So clearly there's a lot more research that needs to be done on lectins and how they actually affect the human body.

Clinically, though, what I have found is there are some people that negatively respond to these foods that contain lectins. And I think in a lot of cases, it's difficult to know if this person is reacting to the lectins themselves in these foods, or they might have the inability to tolerate the fiber in the foods, or maybe they're tolerating a food sensitivity.

Clinically, I have found that some people do negatively respond to foods that contain lectins. It is difficult to know if the person is reacting to the lectins themselves, or if they have the inability to tolerate the fiber in the foods, or maybe they're experiencing a food sensitivity to that food item. It's difficult to know what the cause of the reaction really is.

Methods to reduce lectins in foods

I want to touch again on there are some methods to reduce lectins in foods. Soaking prior to cooking, sprouting, boiling, pressure cooking, all can reduce the amount of lectins in these foods. Now it is time for me to take a short break. And when I get back, I'm going to dive deeper into legumes and nightshades.


Digging deeper into legumes and nightshades

All right, welcome back. Let's talk more about legumes and nightshades. Both groups do have lectins and the listener did ask about them specifically. The legume group, I think it's a lot larger than what people realize. So here are some foods that are in the legume group: lentils, peanuts, rooibos, soybean, beans, like black bean, kidney beans, all of those;

Peas, chickpeas, green beans, snap peas, snow peas. And the legumes that do have the edible pods, they are less likely to be problematic because they naturally contain lower amounts of lectins. And again, the good news is, is soaking and cooking your legumes may almost completely get rid of all the lectins.

In addition to the legumes containing lectins, many legumes also contain phytic acid, which has the potential to be problematic as well. Phytic acid is a storage form of phosphorus found in various different types of plants. Humans can't digest it, but other animals can, but the negative with phytic acid is it can bind the minerals and prevent absorption of them.

It does not leach minerals that are already stored in the body, which is good news, and phytic acid has the potential to interfere with enzymes needed for digestion. I did want to mention that part of legumes as well.

Again, there can be various different reasons why people may negatively react to a food. It may not be the lectins themselves. But I do think if you are having some of these legumes and, you know, maybe one serving a day, then it's, the phytic acid part is probably not going to be an issue. I do have some clients that negatively react to legumes, and it's not always the entire legume group.

It may be that they react to peanuts, or maybe they negatively react to beans. There again is a lot of variability there. Sometimes they trigger digestive symptoms, trigger autoimmune symptoms, or increase pain. But soaking them, pressure cooking them does, again, reduce the amount of lectins. There's a brand of canned beans out there called Eden that does soak and pressure cook their beans before canning them.

But I can think of a client offhand, she doesn't tolerate those either. So, that tells me that she’s not reacting to the lectins in beans; something else about the beans does not agree with her.

Let's move on to the nightshade group. Foods that fall into the nightshade group are white potatoes, not sweet potatoes, tomatoes, eggplant, peppers And this does include a lot of spices like chili powder, cayenne, paprika. This does not include black pepper; tomatillos, goji berries, okra, ashwagandha; all of those also fall into the nightshade category.

And the nightshades, they are a group of botanicals that only contains a small amount of plants that are safe to consume. A lot of plants in the nightshade group are actually very poisonous. Nightshades contain alkaloids, which are lectins. And for the majority of people, again, these alkaloids, they're harmless. They're not going to create an issue.

Specifically, looking at some different types of lectins or alkaloids in this night shade category, solanine and tomatine, they are types of lectins that are produced by the potato and tomato plant. Unripe tomatoes, like green tomatoes and potatoes that have green areas or are sprouting, they have higher amounts of this solanine. So maybe for some people, it's avoiding those types of potatoes or the unripe tomatoes.

There's another molecule in nightshades called saponins that can cause an overreaction of the immune system in some individuals and they may contribute to more autoimmune disease symptoms. But again, I do want to point out eliminating nightshades, that cuts out a lot of different foods and a lot of different dishes. So you're missing out on some delicious, healthy vegetables with fiber and other beneficial nutrients.

I do believe, unless you react to these foods, I would not recommend a complete avoidance of them. I do have some clients, again, kind of similar to the legume group, they may react to some of these foods in the nightshade group and not others. I have some clients that don't tolerate raw tomatoes well, but cooked tomatoes or tomato sauce is much better tolerated.


So once again, a lot of variability here. I do want to just briefly touch on grains. This wasn't part of this individual's question, but grains is one of the groups that does contain high amounts of lectins. Many grains also contain that phytic acid that I mentioned when I talked about legumes. Of course, wheat, you know, one of the most common grains has gluten as well. So does barley, rice, spelt, kamut.

So I think for a lot of reasons, many individuals do not tolerate grains. And something that should be limited or avoided in a lot of people's diets. I also see them spiking people's glucose quite a bit. I think as a whole, I probably see more people react to grains than I do the nightshades and the legumes.

Who might consider eliminating some of these foods?

Let's talk about who might consider eliminating some of these foods. Of course, if you've already recognized you don't tolerate nightshades, legumes, or grains, any of these foods that contain lectins, then avoid them. But, for the vast majority of people, they're probably not going to be an issue. You know, first and foremost, if you have symptoms, you're not feeling your best, I'd encourage you to focus on a diet full of real foods.

That would include protein like meat, eggs, dairy, if tolerated, seafood, fish, getting real carbohydrates like vegetables and some fruits, incorporating the healthy fats like olives, olive oil, butter, avocados, nuts, seeds, and then limiting or avoiding the processed food.

If you feel like you've already done that, but you're still experiencing arthritis pain, autoimmune symptoms, or maybe digestive symptoms, it may be worth exploring some of these foods that do contain lectins. I see these types of foods more likely to affect individuals that have arthritis, digestive symptoms, or autoimmune conditions.

If you are curious, the best way to determine if you're sensitive to a food is to completely eliminate it from your diet. So, eliminate the nightshades or the legumes or maybe both of them together for two or three weeks, then slowly reintroduce them back into your diet. Reintroduce them one at a time.

That's really important. Wait, I would say, three days in between introducing each food. When you do reintroduce them, pay attention to digestive symptoms, energy, pain, autoimmune symptoms, to see if you do have some sort of reaction.

And again, you might react to some nightshades, but not others. You know, I can think of one client in particular that at one point she reacted to all nightshades, but we really focused on healing her gut and she was able to reintroduce some of them. So that could be a possibility for you as well.

And I think, you know, over the last 12 years of being a dietitian, one of the biggest takeaways I have is everyone is different. What works to reduce inflammation or other symptoms in one person may not help the next person. Yes, I think foundationally everybody should be on a diet rich in real foods, getting that protein, carb, healthy fat, like I mentioned, but outside of that, there's just so much variability in what works best for you as an individual.

And that's what we help people to figure out. So if you are overwhelmed at this point, you're maybe unsure if it's worth exploring, eliminating one of these foods, or you want somebody to help you through that process, that is what we do. We would be happy to help you with that. And for more information about counseling, you can visit our website, weightandwellness.com.

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I do want to do a little bit of recap on today's topic, lectins. They are found in plants, and they act as a defense mechanism for the plants themselves. Legumes, grains, and nightshades are some of the foods that contain the highest amount of lectins. However, soaking, boiling, pressure cooking, sprouting, cooking processes can help to reduce the lectins.

For many people, I think it's unnecessary to avoid all of these foods, unless you know for sure that they do create a reaction. Individuals with autoimmune conditions, digestive symptoms, and arthritis, I think, are more likely to react to some of these foods, in my experience, and that is what other clinicians see as well.

So, first and foremost, switching to a real food diet, reduce, eliminate those processed foods, but if you're still having symptoms, maybe explore an elimination of those that, that I talked through how to go about that. And if you need additional help, then check out our website.

I want to thank you so much for listening to Dishing Up Nutrition's “Ask a Nutritionist”. If you happen to find this episode helpful, please be sure to leave us a rating or review on your favorite podcast app so we can help even more people discover the connection between what they eat and how they feel. If you yourself have a nutrition question you would like us to answer, we invite you to join our private Dishing Up Nutrition Facebook community by searching Dishing Up Nutrition on Facebook.

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