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Science over Sciencey-ness: Is it safe to indulge in beans? What about the Lectins?

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Talking about the Paleo Diet always feels dangerous.  It never made sense to me.  When I first brought that up at our CrossFit Box I was warned by a CrossFit trainer not to speak publicly about it.  “They will destroy you.” were her exact words.  Not being sure exactly who “they” were, I’ve written about it, pretty much as delicately as I can, a few times.  I don’t intend to offend anyone, or threaten anyone’s sense of self or loyalties.  But, as a professor and toxicologist (and hopefully responsible citizen) I feel compelled at times to discuss issues of logic and incomplete information when they are potentially damaging to people’s health.    So, in advance, to my Paleo friends . . . I only wish you well.

The Paleo Diet basics.

Most people on the Paleo Diet are trying to lose weight and become healthier.  The paleo diet eschews refined food and junk food.  It also eschews a number of other foods.  Grains are on the “not paleo” list as are beans and peanuts.  The rationale centers around gut inflammation.  Gluten, a plant lectin, is on the “not paleo” list because it causes inflammation in people who have celiac disease.  The paleo diet treats all people as though they have celiac disease.   It is a perfectly normal conclusion to make when immediate experience is the only source of information.    It makes sense on a primitive level.   A gut level.  For most paleo experts the  “medical establishment” and the FDA are misguided at best and are often seen as enemies.   For paleo advocates, there is very little information that can be trusted.  Paleo diet advocates do rely on selected papers published in scientific journals to support their hypotheses.  For a more articulate discussion watch the video below:

lectin Quinoia Paleo? CrossFit Social after CrossFit WOD

Fear of Lectins and anti-nutrients can make people neurotic. Maybe its just fear that makes people neurotic.  Either way its not good for you. Relax and enjoy life.

The Paleo Diet and Lectins and What are Lectins?

Lectins are binding proteins.   Humans, like other organisms, use binding proteins to protect and control various substances in the blood.  Binding proteins help protect hormones from being degraded before they can reach their targets.   Binding proteins can also serve to limit the amount of an active substance in the blood stream.  Binding proteins help the body maintain control of itself and its operations.  Lectins are binding proteins that bind to sugars.  In humans lectins play important roles in

  • Cell communication
  • Cell differentiation
  • Movement of cell vesicles

Why do Paleo Diet Experts think lectin is an anti-nutrient?

The rationale may be that

  • Gluten can harm the gut of people with celiac disease.
  • If some people cannot tolerate gluten, then gluten is probably bad for everyone
  • Gluten is a lectin, therefore lectins are bad for people


Much of the belief that lectins are anti-nutrient seems to come from a single paper published in an open-access online journal called BMC Endocrine Disorders.    It is a “hypothesis paper.”  The authors of the paper make associations between obesity and other diseases of affluence and cereal-based diets.  The paper was published in 2005 and has two citations.   Citations by other researchers are a way to judge the impact of the paper on other scientists.  If your paper gets cited it means that other scientists have referenced your work to support their research.  Two citations in 8 years is not a huge amount . . . and both citations were self-citations. Interestingly, neither of the citing papers discussed lectins.  Hypothesis generation is a worthy endeavor.  A lot of good comes from hypothesis generation.  Hypotheses can be fun and interesting.  And they can inspire research.  But unless the practice of noting associations goes beyond hypothesis generation to hypothesis testing the ideas should stay in the fun and interesting pile and not become a foundation for a diet for millions of people.

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It seems to be true that some lectins can cause intestinal distress.  The Miyake et al. (2007) paper (below) was an investigation of the mechanism by which uncooked lectins cause acute gastrointestinal distress.  Fortunately, cooking breaks lectins down.  Unless you are a big fan of raw beans you will probably have no problem with lectins.   Most people cook beans.  And most people will get a huge stomach ache it they eat them uncooked.  If you do get a huge stomach ache after eating something (a lectin or not) you should probably not eat it anymore.  Our ancestors ate grains.  We are, in most likelihood, well adapted to their consumption.  Uncooked beans are probably another story.  Eat them after they have been cooked.  They are a good source of protein, minerals, vitamins and anti-oxidants.

Science over sciencey-ness

Reasonableness over rigidity



Miyake K, Tanaka T, & McNeil PL (2007). Lectin-based food poisoning: a new mechanism of protein toxicity. PloS one, 2 (8) PMID: 17668065

Jönsson T, Olsson S, Ahrén B, Bøg-Hansen TC, Dole A, & Lindeberg S (2005). Agrarian diet and diseases of affluence–do evolutionary novel dietary lectins cause leptin resistance? BMC endocrine disorders, 5 PMID: 16336696

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