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I just read this articale that shows in table 2 how food preparation effects Lectins. It is said that soaking, boiling, autoclaving, germination and fermentation reduces the concentration, while roasting and baking increases it. I understand that a preparation method can denature lectins. But how can a preparation method increas the concentration of a protein?

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The authors of the paper give no source for their claim that baking and roasting increase lectin content. I cannot find any other source that supports that claim. In general, the tables supplied with that paper lack sufficient citations, and it's just all around a bad paper. It's a "narrative review", whatever that is, and not a study of any kind.

As such, my answer for you is that it's simply wrong, and baking and roasting do not increase lectin content. I would also recommend against giving too much credence to any of the paper's other claims.

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    This is the right answer. One of the papers (Adeparusi 2001) referenced in the section above table 2 in the paper in question actually determined that baking removed lectins completely in Lima beans. Adeparusi published in a respected journal Nahrung/Food, now called Molecular Nutrition and Food Research. I don't see any information on baking in any of the other papers cited in that section.
    – bob1
    Feb 22 at 1:22
  • This is a very good point. I tried to trace where the claim came from in the paper and couldn't find it, and I was going to put a point about that in my answer, but I (wrongly, it seems) assumed it was somewhere.
    – Esther
    Feb 22 at 19:32
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Roasting and baking drive off moisture, therefore concentrating everything else in a food. If a cooking method doesn't significantly reduce the amount of lectins in a food, but it does significantly reduce the amount of water, then the resulting cooked product will have a higher percentage of lectins by weight than the raw product.

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    This is a good thought, but in practice if you look at the foods where lectins could be a concern, this wouldn't happen, and most of the lectins are going to be denatured anyway. It's too broad a statement with no proof or references, and if there is a case where there's more dehydration than denaturation per gram it's going to be an edge case, and you can't make a general statement that this cooking method always produces this result (or even usually).
    – myklbykl
    Feb 22 at 12:26
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First and foremost, lectins are proteins, and like all proteins they can be denatured by heat, cold, acids, bases, fermentation, salts, radiation, and other ways. So, if you cook lectins at a high enough temperature to denature the other proteins in your food (and all plant and animal-based foods contain proteins), then you're also going to denature and deactivate the lectins. There is no known mechanism where cooking would increase the lectin content by converting other molecules into lectins

Second, lectins are found in many foods, though we mostly hear about them in beans (particularly kidney beans (phytohaemagglutinin)). In addition to legumes, they are found in grains, vegetables (such as nightshade), nuts and seeds, dairy, and other foods.

Third, lectins are not as evil as people make them out to be. They can definitely cause problems if eaten in large quantities, and lectins vary in their health consequences. Some lectins (like ricin) are extremely dangerous, and some lectins have some therapeutic uses. But the normal amount of lectins that you eat is fine.

I looked at the table and it seems like nonsense to me. Baking does not generate new proteins magically. The only thing I could imagine is that maybe the authors have misinterpreted something or perhaps believe that lectins that are bound to other molecules that get "released," but that doesn't really make much sense either.

I'll try to do a little more research on this, but in general I can give some advice. I teach a lecture on nutritional epidemiology, and I have studied many theories and papers over the last 100 years, and there are an unbelievable number of mistakes, fraud, p-hacking, and other problems in many studies. And sometimes what looks like a piece of evidence as the result of the study may be true in a very small circumstance depending on how the testing was done, but in general, it's going to be just one piece of evidence in a much bigger picture of a very complicated field.

So, I would say, don't worry about it. I can pretty much guarantee that baking for an appropriate amount of time is going to significantly reduce the lectins in your bread (or whatever).

Since beans are most commonly cited as being sources of dangerous lectins, the advice I give my students is to first soak them for a number of hours (I change my water once but that's not necessary) and that will reduce lectins, phytic acid, and even some of the raffinose. Then boil them for a full ten minutes to denature the remaining lectins before turning down the heat and cooking for the remainder of time and a lower and more gentle temperature.

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  • The only thing I can think of is what Esther’s answer states; if they’re talking about lectin per weight, that could go up as the food dehydrates, but not the total content in a given batch of food. Assuming you’re not decreasing the amount via denaturing, of course Feb 22 at 9:29
  • @fyrepenguin — I thought of that too, but that's just silliness. In order to assert that baking a food increases lectins is if you're comparing against eating that food raw. So we're not talking about wheat or beans or rice. Maybe they're talking about something like a tomato. But still, there's no way that this would increase the number of lectins in it, even if you go by serving size. It is also too broad a statement. There are many ways to bake a tomato. Are you dehydrating it at a very low temperature over a long period of time or roasting it? These would have different results.
    – myklbykl
    Feb 22 at 12:23
  • +1 . And The comment of bob1 under another answer clarified it quite well
    – LulY
    Feb 22 at 13:06
  • @myklbykl I will say that the paper gave me a dim view of "Nutrients" journal's peer review process. Like, why are they publishing this trash? I've never heard of the journal before and I strongly suspect that it's pay-to-publish.
    – FuzzyChef
    Feb 22 at 20:00
  • @FuzzyChef — agreed. I have seen a lot of things published that are highly questionable or plain wrong, yet people trust the source so they believe it. I reached out to one of the authors of this paper and I'll post here if I hear back.
    – myklbykl
    Feb 22 at 21:03

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