What Are Lectins?
Lectins are a type of protein found in a range of foods.
Lectins are grouped together based on the fact they are all proteins that bind to carbohydrates. This feature protects plants in nature. Although it may actually cause issues with digestion as it makes lectins stable in an acidic environment.
The human stomach is acidic to facilitate the breaking down of foods. Lectins are resistant to being broken down in the gut due to being unaffected by this acidity.
There are many different kinds of lectins that all have different effects on the human body.
Ricin, for example, found in castor bean seeds is known to be toxic to humans when consumed, however, not all lectins need to be approached with the same amount of caution.
Some lectins are completely harmless and may even provide health benefits.
What Foods Are High In Lectins
Lectins are found in legumes, soy food, grains, vegetables (particularly nightshades), some nuts including cashews and peanuts, seeds, and some fruits.
Gluten found in wheat products is actually considered a lectin amongst many others found in a wide range of foods.
Lectins are even found in some dairy products (A1 protein is a lectin-like protein), eggs, and meat from animals that have been fed corn and soy.
What Is a Lectin Free Diet?
Dr. Gundry, a medical doctor from America, coined the term lectin-free diet.
He describes lectins as the main danger in the Western diet. That along with sugar, including naturally occurring sugar found in fruit and GMOs.
According to Dr. Gundry, going lectin-free helps people improve health and reduce body weight.
Below is a list of Dr. Gundry’s foods to avoid.
Some foods high in lectins can simply be prepared in a particular way (peeled, soaked, and/or pressure cooked) to reduce the lectin content whilst others need to be completely avoided on the lectin-free diet.
What Is The Issue With Lectins?
Some Lectins Are Poisonous
One of the most well-known and clear reactions in people eating lectins is red kidney bean poisoning. Even small amounts of raw or undercooked kidney beans can cause nausea, vomiting, stomach upset, and diarrhea. Milder effects include bloating and gas.
Red kidney beans contain phytohaemagglutinin, a type of lectin that can cause red blood cells to clump together. However, when these beans are cooked, the harmful lectins are denatured and no longer pose a threat.
Since red kidney beans and legumes, in general, are not consumed raw, their lectin content is nothing to be concerned about. All legumes are going to be difficult to digest unless cooked.
You Can’t Digest Lectins
One of the most cited reasons for removing lectins from someone’s diet is that you “can’t digest them”.
That in itself is true. As previously mentioned, lectins are somewhat immune to the acidic environment of our stomachs that are made to break down foods.
There are actually many kinds of nutrients that cannot be digested completely by the body.
Dietary fiber is a great example of this. Fibre actually stays intact as it moves through the digestive system and our bodies don’t technically digest fiber. This is why a sudden and drastic increase in fiber intake can cause gas, bloating, diarrhea, or constipation.
That does not mean fiber is damaging our digestive system though. Fiber is actually known for nourishing the gut and reducing the risk of chronic disease!
Another example would be FODMAPs.
FODMAPs are a group of carbohydrates also resistant to digestion. For some people who are particularly sensitive to certain FODMAPs, they may experience IBS-like symptoms after consuming foods high in FODMAPs.
But for most people, foods rich in FODMAPs will pose no issue despite not being “well digested” by the body.
For those experiencing gas, bloating and other digestive issues after consuming lectin-rich food there may be merit in reducing their intake. But not by cutting out foods. It could be recommended that they soak their nuts, seeds, and legumes and cook all other foods well to reduce lectin content.
Lectins Reduce Nutrient Absorption
Active lectins found in foods like grain, nuts, and legumes can interfere with the absorption of some nutrients including iron, zinc, and calcium.
This is because lectins bind to the lining of the digestive tract.
However, many plant-based foods contain an array of what we call anti-nutrients. For example, phytates and oxalates are also found in vegetables, grains, and legumes, and tannins in tea and coffee.
All of these nutrients are known to hinder the absorption of other helpful nutrients. But that doesn’t make the foods that contain these ‘anti-nutrients’ harmful to our health.
From a nutrient absorption perspective, there is some merit in increasing daily intakes of some nutrients affected by these anti-nutrients. Especially if plant-based foods are your main source of things like iron, zinc, and calcium.
For vegetarians and vegans, the recommended daily intake of iron is 80% greater than non-vegans and zinc intake should be 50% greater. These recommended daily intakes take into account the reduced absorption of these nutrients from plant-based foods.
But it is useful to note that it is not only lectins but a range of anti-nutrients that are responsible for this.
Nonetheless, if you do have a reasonable amount of animal products in your diets such as meat, seafood, and dairy, you do not have to worry as much about the reduced absorption of nutrients in some of your foods because you are also consuming sources with high absorption rates.
They Cause Weight Gain & Disease
In 2018, singer Kelly Clarkson stated in an interview that her 17kg weight loss and remission of a thyroid issue was due to taking on a lectin-free diet.
She had read Dr. Gundry’s book, The Plant Paradox which had just been published a year prior.
According to Gundry, lectins can cause weight gain, gastrointestinal disorders, autoimmune disorders, and allergies.
A large majority of the evidence he cites tends to be the anecdotal results of his patients and followers such as Kelly Clarkson.
When it comes to actual scientific evidence, research into lectins is pretty slim pickings.
Extrapolating this type of research to humans is a big leap of faith and is often more of a hindrance to nutrition science than it is helpful.
In fact, research (in actual humans) shows that those on a predominantly plant-based diet that is rich in whole grains, nuts, seeds, legumes, fruit, and vegetables tend to have a lower risk of obesity and chronic disease.
So if these anti-nutrient-containing foods were so harmful to our health, why do the people eating a larger amount of them have better health outcomes?
Doctor Gundry’s stance on lectins is controversial and is actually in opposition to current nutrition recommendations and population research.
Although interestingly, a 2019 review of studies highlighted the fact that a lectin-free diet may benefit people with inflammatory bowel disease and multiple sclerosis. This isn’t to say a lectin-free diet is the way to go for everyone with these conditions, particularly with only a small pool of research, but it could be a space to watch.
What Are The Health Benefits Associated With Lectins?
Lectins potentially have a number of health benefits.
Some lectins act as antioxidants that protect the body’s cells from damage.
They also slow the digestion and absorption of carbohydrates which can help you stay fuller for longer and prevent sharp increases in blood glucose levels.
There is some research into lectins as anticancer treatments but research here is still in its early days.
Furthermore, there is a wide array of research showing that lectin-containing foods such as legumes, whole grains, nuts, and seeds are associated with lower rates of type 2 diabetes, cardiovascular disease and are helpful for maintaining a healthy weight.
These foods are also great sources of many nutrients such as healthy fats, fiber, vitamins, and minerals.
Certain lectins can be harmful when consumed, therefore it is important to cook your legumes before consuming them. Especially red kidney beans.
But when it comes to lectin-containing fruits, vegetables, nuts, and seeds, there is nothing to worry about. In fact, diets rich in these foods have been shown to have great long-term health outcomes.
If you are struggling with digestive issues, there may be some merit in soaking, sprouting, fermenting, and cooking certain foods to reduce the lectin content.
These preparation methods can also reduce the contents of a number of anti-nutrients in foods, leading to better absorption of some micronutrients.
So even though Dr. Gundry has cooked up a compelling story, there is no need to take up a lectin-free diet.