Geschatte leestijd: 6 minutenAn remarkable assertion by an American heart surgeon: The lectins in certain vegetables, nuts, and whole grains are, according to him, the greatest danger in the Western diet. Remarkable because we normally receive advice to eat more of these.
Complete confusion over whole grains
Well, last week I wrote an article about the benefits of replacing refined grains with whole grains. By refining grains, you also discard many important nutrients such as fibers, vitamins, and minerals. But your mother probably already told you that whole wheat bread is healthier than white bread.
As always, nothing regarding nutrition is simple. Just when I thought I had nicely explained why Mom was right, some clown comes along with a book warning about the dangers of certain vegetables and whole grains. You’re supposed to replace whole grains with refined grains. Well, ‘clown’, Dr. Stephen Gundry is a heart surgeon. You might consider surgeons as the cowboys among doctors, but the title makes it difficult to dismiss his opinion outright. Moreover, what this surgeon claims in the book “The Plant Paradox” is not entirely baseless. There is a theoretical basis for his assertions, but this is no reason to follow his dietary advice.
“Revolutionary diet”
I’m always wary of these types of publications. When people pinpoint one type of food or nutrient as the source of all evil on Earth, I’m skeptical. In reality, nutrition and metabolism are complex. A simple explanation within this complex process is almost always incorrect or incomplete and aimed at the public’s need to have complicated matters presented simply. For credibility, a fixed protocol is often followed: You take one or several demonstrable facts and build a theory around them that is less or not at all substantiated. Then you figure out how to cash in on it.
In the case of Dr. Stephen Gundry, lectins are the antichrist. The fact that they can have a toxic effect is one of the demonstrable facts. That they are the greatest danger in the Western diet is subsequently the theory for which there is insufficient scientific basis.
The latter doesn’t matter for commercial success either. What works is a ‘revolutionary new insight’, preferably one that radically contradicts established knowledge about healthy nutrition. This is evident from the subtitle of the book: The Hidden Dangers in “Healthy” Foods That Cause Disease and Weight Gain. Convenient, of course, to mention body weight in the title as well. There are enough people who are not so much concerned about their health but do want to be slimmer. Better book sales then.
As long as you sprinkle enough snippets of scientific data and carry the title of doctor, this is enough for many. If you link this new insight to extreme dietary recommendations, celebrities are eager to capitalize on the latest trend, and the rest of the world quickly follows. Finally, you introduce a line of supplements that counteract the effects of the public enemy No. 1 you discovered hiding in vegetables, fruits, and whole grains. After all, you earn more from the crowd buying your supplements than from boycotting healthy food. Why stop at book sales revenue?
Lectin
Dr. Gundry identifies lectins as the source of many health problems and diseases. Lectins are a type of protein that binds to large carbohydrates. Over the past years, many different types of lectins have been found in various plants, vegetables, and fruits. It’s often the seeds that contain many lectins. Legumes, in particular, can contain a lot of lectins.
Dr. Gundry explains that evolutionarily, lectins form a plant’s defense system against insects. Because humans have many more cells, the damage from lectins would only manifest over the course of years. This would result in allergies, autoimmune diseases such as rheumatoid arthritis, ‘brain fog’ (clouding of consciousness), acne, eczema, and irritable bowel syndrome, among other things.
He goes on to say that they can penetrate our joints, nervous system, and blood vessel walls, causing inflammation and autoimmune diseases. They may even be the cause of most cardiovascular diseases. Here again, a mix of facts (the first part) with an associated unfounded assumption.
According to Dr. Gundry, you should immediately stop eating all kinds of fruit. Although, avocado is allowed. That’s not normally the first thing you think of for your two pieces of fruit a day. The new recommendations for more legumes in the “food pyramid” were a total blunder. Legumes such as peas, soy, and kidney beans, cashews, and peanuts should all be avoided. But also the seeds of tomatoes, red peppers, and eggplants should be avoided according to Dr. Gundry.
And of course, the word I mention here with great reluctance: Gluten. Gluten, as in whole grains, contains traces of a type of lectin (wheat germ agglutinin). A type of lectin that cannot be reduced by cooking or other processing like the lectin in beans.
But that’s precisely the brilliance of Dr. Gundry’s theory. You can hardly avoid lectins because they occur in so many plant and animal foods, averaging 30% of the food people consume. So, to counteract the harmful effects of lectins that you still consume, you can buy his supplements for about 65 euros a month. Ka-ching!
Lectins are toxic
In Breaking Bad, ricin played a few nice supporting roles as Walt’s poison of choice. Just a bit of ricin in powder form the size of a few grains of salt can be lethal to an adult. Lectins were first identified in 1888 by the German microbiologist Peter Stillmark. He isolated and distilled the proteins in the seeds of the castor bean (Ricinus communis, the source of castor oil). This yielded ricin, a form of a certain type of lectin (hemagglutinin).
The introduction of lectins in this extremely toxic form fits nicely into Dr. Gundry’s story, but since then, many other lectins have been found. We also now know some important functions of lectins in the body. Lectins play a role in cell binding, cell division, and interaction between cells and sugars.
In addition, lectins can also have harmful effects. A large portion of the lectins in our diet is broken down before they reach the bloodstream. Because they can bind with other nutrients (which can then not follow their normal path), they can theoretically lead to deficiencies in certain nutrients, disrupted digestion, and damage to the intestines. However, this only happens with very large amounts of lectins or with a lack of functional enzymes that counteract this effect. Moreover, the body also has antibodies against the effects of lectins. The absence of such antibodies (when proven in research) can be a concrete reason to avoid lectins.
Hunger makes raw beans sweet
The potential danger of lectins is not news. In 1988, a British hospital organized a “healthy eating day”. One of the dishes contained kidney beans, of which 31 portions were served. At 3 o’clock in the afternoon, an operating room assistant began vomiting in the operating room. In the next hour, this example was followed by 10 colleagues who began vomiting heavily and, in some cases, experiencing diarrhea. Everyone was recovered the next day. Research found none of the usual pathogens or toxic substances. Eventually, the search was narrowed down to the large amounts of a type of lectin, phytohaemagglutinin. Five raw beans can contain enough of this type of lectin to have a toxic effect and cause symptoms like those experienced on that day of healthy eating. However, by properly cooking the beans, the amount of this lectin is reduced by a factor of 200. There are many other types of food of which everyone knows that intake in raw form can be dangerous. Many of the dangers of large amounts of lectins can therefore be prevented by proper preparation. I wouldn’t test the saying ‘hunger makes raw beans sweet’ in practice.
There are many studies to cite that show positive and negative effects of lectins. There are also studies that show lectins can reduce the risk of tumors and cancer. Ultimately, the question is whether lectins and the foods they are in do more harm than good on balance. There are no studies pointing to this.
Oxygen can also be toxic under various conditions. Oxygen is necessary for many chemical reactions in the body. However, this ‘oxidation’ also produces by-products such as free radicals that can cause damage. Yet, no one is suddenly going to breathe their breath permanently. Whatever the potential downsides of oxygen may be, it is clear that the benefits are many times greater.
Lectins in the diet: The studies
The easiest way to investigate the disadvantage or advantage of lectins is by comparing the effect of a diet high in lectins with a diet low in lectins. This way, you also approach the practice better.
Some of these studies I’ve recently mentioned in the article about whole grains versus refined grains. From the studies discussed there, it appeared that replacing refined grains (low in lectins) with whole grains (high in lectins) had several benefits:
- Participants ate less and had lower weight
- Lower risk of diabetes
- Lower risk of cardiovascular diseases
- Lower risk of death
Most governments rightly advise choosing whole grains. We could also mention the benefits of sufficient vegetables and fruits here, but this article has already become too long to add dozens of studies that, let’s be honest, tell nothing new. One diet whose added value for health has been repeatedly demonstrated is the Mediterranean diet. Let that consist of many plant-based foods, whole grains, legumes, and nuts. The opposite of a lectin-free diet.
Dr. Gundry selectively highlights some potential effects of lectins but doesn’t put it in the right context and misses the bigger picture. This may be interesting for people with certain sensitivities or conditions, but it says little about the effect in healthy individuals. Avoiding lectins thus avoids a lot of the beneficial nutrients that foods containing lectins also provide. It’s very unfortunate that a doctor writes such a book because it causes confusion, ambiguity, and goes against generally accepted knowledge about healthy nutrition. So, keep eating your vegetables, nuts, legumes, and fruits.
References
- Kolberg J, Sollid L. Lectin activity of gluten identified as wheat germ agglutinin. Biochem Biophys Res Commun. 1985 Jul 31;130(2):867-72. PubMed PMID: 3839672.
- Vojdani A. Lectins, agglutinins, and their roles in autoimmune reactivities. Altern Ther Health Med. 2015;21 Suppl 1:46-51. Review. PubMed PMID: 25599185.
- Gilbert RJ. Healthy eating day. Communicable Disease Report. 1988;33:3–4.
- Dang L, Van Damme EJ. Toxic proteins in plants. Phytochemistry. 2015Sep;117:51-64. doi: 10.1016/j.phytochem.2015.05.020. Epub 2015 Jun 7. Review. PubMed PMID: 26057229.
- Jonnalagadda SS, Harnack L, Hai Liu R, et al. Putting the Whole Grain Puzzle Together: Health Benefits Associated with Whole Grains—Summary of American Society for Nutrition 2010 Satellite Symposium. The Journal of Nutrition. 2011;141(5):1011S-1022S. doi:10.3945/jn.110.132944.
