Lectins and Eat Right 4 Your (Blood) Type

I’ve had an email in my inbox for a long time asking me about lectins. Lectins are one of those topics that are pretty hard to research because there are so many people saying so many different things with mostly animal and in vitro research to back them up. There are few studies on humans to really make any definitive claims. So, an article on lectins is almost tantamount to just taking a poll and seeing what most people who are talking about them think – not the best way to do a review. In any case I have spent a number of hours over the last week reading up on lectins and here is what I’ve found, about which I am relatively confident:

Lectins are proteins found in many plants that can attach themselves to carbohydrates on other proteins. The biggest concern is their ability to attach to the proteins on the lining of our digestive tracts causing acute digestive problems. Uncooked legumes contain the largest amount of and most potent lectins.

Personal example: I once ate a bowl of blended, uncooked black beans, while experimenting with raw foodism long before I was a dietitian, and the result was remarkable to say the least – I don’t recommend it.

Another example is ricin, a lectin from castor beans that can be deadly due to its ability to bind proteins involved in the synthesis of other proteins.

Most lectins are not quite as problematic and can be deactivated by cooking. However, cooking will not necessarily deactivate all of the lectins commonly found in plant foods such as legumes, grains, and night shades.

In his book, Eat Right For Your (Blood) Type, Peter D’Adamo takes the idea of lectins a step further and suggests that lectins that happen to get absorbed into the blood attach to blood cells and cause them to clump together leading to clogging of the arteries and resulting in heart disease. There does not seem to be any significant evidence for this and given how much atherosclerosis has been studied, it would seem that by now we’d know lectin-clumping was a problem if it really was part of the etiology of heart disease. Even after 15 years, Dr. Michael Klaper’s article on the blood type diet is still, to my knowledge, the best response to this theory:

Challenges to the Plant-Based Diet in the 90’s: “The Zone” and “Blood-Type” Diet Fads

A 2013 thorough review of the literature found that there have been no clinical trials published that have tested the Eat Right For Your (Blood) Type diet (1).

Aside from heart disease, should you be worried about lectins? Doubtful. But if you have regular digestive problems, particularly something akin to irritable bowel syndrome, it might be worth considering which foods you might be eating that are high in lectins such as legumes (especially if not thoroughly cooked), whole grains, or night shades, to see if limiting such foods can give you some relief. And although I think it’s much less likely than for digestive problems, if you have unexplained arthritis, lectins might be worth considering.

I happen to be a big fan of vegans eating plenty of legume products for the protein, zinc, and, for women, iron. So if you do cut back on legumes, please make sure you replace nutrients you might be missing from them. See VeganHealth.org for more info on protein, iron, and zinc.

Here are the best articles I found on lectins, starting with an article from Mark’s Daily Apple, a paleo blog. While I am not the biggest fan of the paleo movement, I thought his article was pretty decent:

The Lowdown On Lectins

Fellow veg RD, Ryan Andrews, from Precision Nutrition weighs in on lectins:

All About Lectins

Boring, but the most scientifically detailed article (that I trusted):

Plant Lectins – Cornell University College of Agriculture and Life Sciences

The End

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1. Cusack L, De Buck E, Compernolle V, Vandekerckhove P. Blood type diets lack supporting evidence: a systematic review. Am J Clin Nutr. 2013 Jul;98(1):99-104. | link

4 Responses to “Lectins and Eat Right 4 Your (Blood) Type”

  1. Kathleen Says:

    Thanks for the laugh, Jack! I too tried some sprouted beans when I was raw, and OH BOY! 😉

  2. Mike Says:

    Anything to worry about wrt lectins and phytates in tofu and soy milk or have these compounds been removed/deactivated during production?


  3. Jack Norris RD Says:


    Phytates are nothing to worry about assuming you have a varied diet and are not prone to iron deficiency. As for the lectins, I wrote everything I know about them in my post above.

  4. EIYLTEM-type visitor Says:

    Hi Jack,

    Thanks for continuing this great work you do! I haven’t read all your links, but I was reading a related article and wanted to see if you agree — I’d warn people not to rely exclusively on slow cookers to cook their beans! Ya want them to BOIL at least some of the time… Slow-cooking chili w/at-least-partially-cooked beans might still work, but anyhow: that’s my top takeaway from the news about legumes and lectins.

    The generalizations about prehistoric societies offered at the beginning of the blood type book are embarrassing, or they would be if he’d ever taken an anthropology class.

    That anyone finds use in the diet to me lends support to claims from K. Fine (for example) that gluten sensitivity may be way more prevalent than previously thought. But that’s just me extrapolating.

    Do cook your beans nice and hot, though!

    Best wishes to you.


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