Blog | Friday, September 8, 2017

Do we dare to eat lectins


In The Love Song of J. Alfred Prufrock, T.S. Eliot's protagonist asks, chewing on mortality and the pangs of senescence, if he dares to eat a peach. We can all thank Dr. Steven Gundry for upping the ante, and asking if any of us dares to eat chickpeas or eggplant; apples or oats; beans or lentils; or for that matter, almost any fruit, many vegetables, and most beans, legumes, grains, and certain nuts. His answer is: no. His reason is: lectins.

What are lectins? I am tempted to suggest to all Harry Potter fans that they are to us muggles what Nargles are to witches and wizards: an enigmatic if not imaginary threat in unexpected places, of concern only to the eccentric.

But I suppose a bit more explanation is in order. Lectins are a family of proteins found in many plants, dairy, yeast, eggs, and seafood that can bind to other molecules, notably sugar and carbohydrate molecules, that are present both in foods, and in the membranes of our cells. The case made in The Plant Paradox is that the binding of lectins from plant foods to our cells is a major cause of ill health, and thus we must all fear and avoid lectins, and the rather dire foods like apples that sinisterly serve as their delivery vehicles. (For whatever it may be worth to you and Prufrock, peaches happen to be a negligible source.)

This, of course, is utter nonsense.

For starters, the reality of lectins is far more nuanced than the sound bites, scapegoats, and silver bullets of formulaic best sellers in the diet category. The scientific literature raises theoretical concerns about the potential toxicity of lectins in certain contexts, but also suggests the possibility of unique health benefits related to cancer prevention, and gastrointestinal metabolism. Lectins are far more active in binding to our cells when consumed at high concentration and in isolation, as they are in experiments, than when consumed in food, as they generally are by actual humans. Cooking often attenuates the binding action of lectins, or causes them to bind to other compounds in food.

In that regard, perhaps a new dietary fad predicated on misguided lectin-phobia has one redeeming characteristic: it serves up an argument against another faddish concept, nearly as silly. The fiercest proponents of raw food diets contend, falsely, that raw is always better. While some foods are more nutritious raw, others, like chickpeas, beans, and lentils, to name just a few, are decisively so when cooked. The raw food argument, in other words, is itself overcooked, and the lectin scare perhaps does us the modest service of shining its little light there.

As for all the rest, it is instead propagating shadows of doubt where none are warranted.

This is not the first time we have been warned away from fruits and vegetables, beans and legumes, nuts and grains. Both low-carb and gluten-free diet advocacy foreswear whole grains, despite overwhelming evidence of the health benefits they consistently confer on all but the constitutionally intolerant. Both low-GI and fructose-is-toxic dietary platforms have caused people, intentionally in the first case and perhaps unintentionally in the second, to abandon fruit, despite overwhelming evidence of its role in defending us even against the very concerns associated with high-glycemic foods and excess fructose, notably type 2 diabetes. We abandoned nuts in the throes of misguided applications of advice to reduce dietary fat intake, somehow reaching the conclusion that Snackwells were good for us, while almonds were not.

This decades-long parade of dietary fads and fashions, an incessant sequence of nutritional misadventures demonstrate one thing above all others: there is more than one way to eat badly, and we the people of the United States seem committed to exploring them all. If you have a new version of dietary nonsense to sell, put it in a book, and we will buy it.

Our history is testimony to the triumph of naïve nincompoopery over experience, to the conclusion that desperation breeds gullibility. Sorry, I must be in a timorous mood today; next time, I'll tell you what I really think.

We have been talked into the claim that gluten and wheat are the source of our many ills, despite the salient presence of wheat in the human diet for 15,000 years or so, it's nominal role for 100,000 or more; despite the presence of whole wheat in the diets of the world's most vital and longest-lived populations; and despite a bounty of evidence of every description demonstrating the predominance of benefit. We have been talked into blaming our metabolic misfortunes on all grains, despite an even more compelling body of evidence linking whole grain intake to almost every health benefit imaginable, including marked reductions in the very degenerations of function and cognition for which whole grains have been falsely maligned.

An effort is afoot to talk us into dismissing the liabilities of excess salt consumption on theoretical grounds, even as a massive epidemiologic study looking agnostically at the associations between dietary components and death found salt to top the list. Personally, I don't think salt, per se, is public nutrition enemy number 1; rather, I think a high concentration of sodium is one of the most consistent indicators of hyper-processed foods that are bad for us in many ways. But that's a topic for another day.

For now, the new contention that we should avoid all of the most nutritious plant foods, including many vegetables, nearly all fruits, all beans, and all legumes because they contain lectins, takes nutritional nonsense to a whole new level. Following this advice will decimate the quality of your diet, and for anyone who actually sticks with such silliness over time (an unlikely eventuality with any diet), your health.

The case being made against most of the foods most reliably linked to vitality and longevity suffers from several fallacies common to all manner of nutritional nonsense. One is to prioritize a theoretical concern (or hope) over the prevailing pattern of outcomes among actual people.

Another is the conflation of a change in the dialogue about some threat with a change in the threat itself. In 2015, for instance, the International Agency for Research on Cancer (IARC), a subsidiary of the World Health Organization, declared processed meat, bacon, pepperoni, and such, a class I carcinogen. There was widespread media coverage, the customary hyperbole, and something nearing panic among the “I have never met a slice of bacon I didn't like” crowd.

But, of course, such a response made no real sense. Yes, processed meat is bad for you, and yes, you'd be better off not eating it. And yes, eating it is rather bad for our fellow creatures and the planet, too.

But the risk from one day to the next changed not at all. Whatever your risk for cancer had been all along, it remained exactly the same the day after the IARC determination was announced. All that had changed was the official position on the matter of that risk. Similarly, the lectins that are in your hummus this week were there last week, too.

The idea that you should renounce many of the foods most decisively and consistently linked to good health outcomes because they contain a compound that can be called a toxin may be the most egregious example of missing the forest for the trees I've ever seen, and I've spent my career scrutinizing, and repudiating, just that variety of nonsense. For the sake of false promises dangling from one gilded tree, this is a case of burning the forest down.

The answer to, “should you fear lectins now?” is, yes, if and only if you do the same for oxygen.

As I recently noted to a colleague, oxygen is not a theoretical toxin with theoretical harms in people; it is a known toxic with established harms. The atmosphere of our planet is thus highly analogous to the dietary sources of lectins: both contain compounds with potentially toxic effects, but net benefit is overwhelming both from eating plants, and breathing.

So, do you need to fear lectins now? Dr. Gundry, who reportedly will be happy to sell you supplements to replace the nutrients present in the foods he is telling you not to eat, says: yes.

I say: hold your breath, and count to a thousand while contemplating the theoretical toxicities of oxygen. Long before you finish, the truth will likely come to you in a gasp.

David L. Katz, MD, FACP, MPH, FACPM, is an internationally renowned authority on nutrition, weight management, and the prevention of chronic disease, and an internationally recognized leader in integrative medicine and patient-centered care. He is a board certified specialist in both Internal Medicine, and Preventive Medicine/Public Health, and Associate Professor (adjunct) in Public Health Practice at the Yale University School of Medicine. He is the Director and founder (1998) of Yale University's Prevention Research Center; Director and founder of the Integrative Medicine Center at Griffin Hospital (2000) in Derby, Conn.; founder and president of the non-profit Turn the Tide Foundation; and formerly the Director of Medical Studies in Public Health at the Yale School of Medicine for eight years. This post originally appeared on his LinkedIn account.