• Your life and health are your own responsibility.
• Your decisions to act (or not act) based on information or advice anyone provides you—including me—are your own responsibility.


Anti-Nutritionism, L-Canavanine, And The Limitations of N=1 Self-Experimentation

What Is Nutritionism?

While I disagree with Gyorgy Scrinis (and the popularizer of the concept, Michael Pollan) on their proposed solution, I believe Scrinis’ concept of “nutritionism” as an error in dietary thinking has merit—and I doubt anyone in the paleo community would disagree.

Reducing food to its nutrient components could be called “nutritionism”, and it has probably become the dominant way of thinking about food and health, and of constructing healthy diets.

The nutrition industry has implicitly, if not explicitly, promoted nutritionism by continually framing most research studies and dietary advice in terms of these chemical-nutrient categories.

The rise of nutritionism is clear in one of the well-known sayings promoted by the food industry and some nutritionists: “There is no such thing as good and bad foods, only good and bad diets.” According to this argument, all types of foods, including junk food, have a place in a “balanced” diet.

Marketing foods and diets on the basis of their nutritional composition tends to take attention away from the quality and the type of foods being promoted.

Processed foods, for example, are often fortified with vitamins and minerals, or stripped of some of their fat, to enable such nutrient-content claims to be made. Nutrient claims on the labels of processed foods and drinks conceal the fact these foods are typically high in added fat, sugar, salt, chemical additives and reconstituted ingredients, and have often been stripped of a range of beneficial micro-nutrients and food components.”

High in protein, low in fat and too good to be true, Gyorgy Scrinis, Sydney Morning Herald, April 7, 2006

Nutritionism makes several unspoken assumptions:

  • We already know all the important nutrients and their functions.
  • The function of an isolated nutrient (even in a synthetic form not occurring in nature, e.g. folic acid) is exactly the same as its function in food, because…
  • There are no competitive or synergistic effects between the thousands of chemical compounds found in one bite of real food.
  • The effect of a food on health is reducible to its effects on the numbers obtained from cheap, easy tests like “BMI” and “total cholesterol”.
  • Therefore, so long as our diet contains the proper “nutrients”, we will be healthy and happy.

I doubt anyone in the paleo community disagrees with Scrinis (and Pollan) that nutritionism, in its modern form, is bunk. A diet of chicken nuggets, Twinkies, and Diet Coke is not nutritionally equivalent to a diet of fresh meat, fruits, and vegetables no matter how many supplements we take.

What Is Anti-Nutritionism?

Unfortunately it’s possible to fall into an analogous trap when pursuing a paleo way of life…a trap I call “anti-nutritionism”. Anti-nutritionism also makes several unspoken assumptions:

  • We already know all the important anti-nutrients and their functions.
  • The function of an isolated anti-nutrient is exactly the same as its function in food, because…
  • There are no competitive or synergistic effects between the thousands of chemical compounds found in one seed, sprout, fruit, or bite of plant or animal tissue.
  • Herbivorous, seed-eating mice—especially genetic knockout mice—are metabolically and biochemically the same as humans, and are excellent models for human digestion and metabolism.
  • Therefore, if I eat a food for six months and I don’t get any fatter or suffer obvious health problems, I can recommend it to others as healthy—and perhaps even paleo-compatible.

Food Doesn’t Want To Be Eaten

It’s tempting to believe that if a food we like doesn’t contain gluten, excessive omega-6 fats, or excessive fructose, that it’s fine to eat. However, all food has defenses against being eaten—because any plant or animal that was eaten before it reproduced failed to leave descendants!

This leads us to a tautological but astonishing conclusion. Every living thing on this Earth is the descendant of millions of generations of successful ancestors—not a single one of which was eaten, trampled, gored, poisoned, burned, drowned, starved, fell from a tree, killed by parasites or infection, or otherwise died before it managed to reproduce at least once.

“Being eaten” certainly qualifies as a reproduction-limiting event. Animals can hide, run away, or counter-attack—but plants cannot. Therefore, we might expect their defenses to involve being disgusting, poisonous, or indigestible—particularly for seeds, their agents of reproduction.

Fruit is the exception to the rule, but there’s an unspoken bargain involved: “eat this delicious, sweet fruit, but don’t digest the seeds…poop them out somewhere else.” As we’d expect, the seeds of most sweet fruits range from bitter to frankly poisonous.

Many books, websites, and scientific papers explore the biochemistry of anti-nutrients like gluten and gliadin (found in wheat and its relatives) and lectins (found in just about every plant seed), and I won’t rehash the biochemistry here. But just as our knowledge of the nutrients in food and their function is incomplete, our knowledge of anti-nutrients is, if anything, far more incomplete.

A Partial List Of Plant Toxins

Lectins, trypsin inhibitors, antigenic proteins, cyanogens, tannins, quinolizidine alkaloids, glucosinolates, saponins, phytoestrogens, non-protein amino acids…

Today’s Unsung Anti-Nutrient: L-Canavanine

To illustrate the limitations of the paleo community’s understanding of anti-nutrients, here’s an example I’ve never seen mentioned by any paleo source: L-canavanine.

(Update: Though it makes no appearance in the literature, apparently Dr. Loren Cordain has indeed been discussing L-canavanine in his speeches and presentations. Thanks to Pedro Bastos for the correction.)

“L-canavanine is a common non-protein amino acid found naturally in alfalfa sprouts, broad beans [also known as “fava beans”], jack beans, and a number of other legume foods [including sword beans] and animal feed ingredients [1] at up to 2.4% of food dry matter. This analog of arginine (Figure 1.) can also block NO synthesis [2-5], interfere with normal ammonia disposal [6,7], charge tRNAarg, cause the synthesis of canavanyl proteins [8], as well as prevent normal reproduction in arthropods [9] and rodents [10].

Canavanine has also been reported to induce a condition that mimics systemic lupus erythematosus (SLE) in primates [11,12], to increase antibodies to nuclear components and promote SLE-like lesions in auto immune-susceptible (e.g., (NZB X NZW)F1) mice [13].” (Brown 2005)

Stated plainly: canavanine “looks” like arginine, and is incorporated into our tissues like arginine…but the resulting proteins don’t function properly. And did I hear someone say “lupus”?

Arthritis Rheum. 1985 Jan;28(1):52-7.
Effects of L-canavanine on T cells may explain the induction of systemic lupus erythematosus by alfalfa.
Alcocer-Varela J, Iglesias A, Llorente L, Alarcón-Segovia D.

Alfalfa sprouts can induce systemic lupus erythematosus (SLE) in monkeys. This property of alfalfa sprouts has been attributed to their non-protein amino acid constituent, L-canavanine. Occurrence of autoimmune hemolytic anemia and exacerbation of SLE have been linked to ingestion of alfalfa tablets containing L-canavanine. In this report we show that L-canavanine has dose-related effects in vitro on human immunoregulatory cells, which could explain its lupus-inducing potential.

Rheum Dis Clin North Am. 1991 May;17(2):323-32.
Dietary amino acid-induced systemic lupus erythematosus.
Montanaro A, Bardana EJ Jr.
“In this article, we detail our experience with a human subject who developed autoimmune hemolytic anemia while participating in a research study that required the ingestion of alfalfa seeds. Subsequent experimental studies in primates ingesting alfalfa sprout seeds and L-canavanine (a prominent amino acid constituent of alfalfa) is presented. The results of these studies indicate a potential toxic and immunoregulatory role of L-canavanine in the induction of a systemic lupus-like disease in primates.”

L-canavanine, being an amino acid, is not deactivated by heat or cooking. So when we hear statements like “Beans are fine so long as you soak or sprout them”, it’s worth reminding ourselves that this isn’t even true according to the tiny fraction of legume biochemistry we understand—let alone the overwhelming majority we don’t.

Further Reading

J. Agric. Food Chem. 2003, 51, 2854−2865
Nonprotein Amino Acids of Plants: Significance in Medicine, Nutrition, and Agriculture
E. Arthur Bell

“Much more needs to be learned of the biological activity, the relative toxicities of these compounds to different organisms, and their nutritional value if we are to make the best use of them and the plants in which they are synthesized.”

Autoimmun Rev. 2006 Jul;5(6):429-35. Epub 2005 Dec 29.
Role of non-protein amino acid L-canavanine in autoimmunity.
Akaogi J, Barker T, Kuroda Y, Nacionales DC, Yamasaki Y, Stevens BR, Reeves WH, Satoh M.

Am J Clin Nutr November 1995 vol. 62 no. 5 1027-1028
Reply to NR Farnsworth
Victor Herbert

Also note that you’ll find a much-copied reference on the Internet claiming that canavanine toxicity is irrelevant to humans. Don’t be misled: it’s an article from a 1995 vegetarian journal which makes a host of blatantly false claims, such as “There is NO canavanine at all in other legumes that are commonly used as human food.”

Favism: A Postscript to the Fava Bean/Broad Bean Issue

Canavanine toxicity is distinct from vicine toxicity. Vicine (and its analogs covicin and isouramil) is a poison in fava beans that causes hemolytic anemia in susceptible people—a sometimes-fatal condition known as favism. Favism is caused by G6PDH deficiencies, common X-linked mutations which affect over 400 million people worldwide, mostly in Africa, the Middle East, and southern Asia.


The Limitations Of Self-Experimentation and N=1

Self-experimentation is very important, and we can learn much that is useful from it. For instance, trying to dial in carbohydrate intake can be a balancing act between weight loss, mood, and physical performance. People have found solutions to their own individual health issues via anything from egg yolks to beef liver to coconut oil to magnesium supplementation. And just coming up with a new repertoire of healthy, paleo-compatible foods to replace the pantry full of junk we used to eat involves extensive N=1 with new recipes—with immediate success not guaranteed.

However, there are limits to the knowledge we can accumulate. Stated plainly:

N=1 self-experimentation can tell us what works best for ourselves—within the limits of healthy eating, as defined by biochemistry and evolutionary context.

However, self-experimentation alone cannot tell us which foods are healthy to eat, because even a dramatic increase in lifetime risk is vanishingly unlikely to manifest itself during a few months of self-experimentation.

For instance, here’s a seemingly reasonable statement:

1. “I ate corn for six months, and I didn’t gain weight or feel worse. Therefore corn is healthy to eat.”

It’s certainly tempting to make these sorts of statements—but I find that temptation is best resisted. To illustrate why, here’s an equivalent statement that we can all agree isn’t reasonable:

2. “I started smoking six months ago, and I feel fine. Therefore smoking is healthy.”

Permit me to drive the point home with force:

3. “I started eating strontium-90 six months ago, and I haven’t got cancer yet. Therefore radiation exposure is healthy.”
4. “I started shooting heroin six months ago. It’s solved all my anxiety issues, and I’ve lost twenty pounds! Therefore shooting heroin is healthy.”
5. “I started having unprotected sex with Tanzanian hookers six months ago, and I feel great! Therefore unprotected sex with high-risk strangers is healthy.”

The reason we can identify the second through fifth statements as false is because we don’t trust the results of our own self-experimentation. We know that long-term observations show that smoking greatly increases our risk of several forms of cancer and heart disease; each Sievert of radiation exposure causes a 5-10% increase in cancer deaths (Strom 2003); heroin addiction is almost never a controllable vice; and HIV infection takes longer than six months to produce symptoms of AIDS—no matter how we feel in the short term.

No, I’m not directly comparing eating corn to smoking or unprotected sex with high-risk strangers! I’m demonstrating that even a substantial increase in lifetime risk is vanishingly unlikely to manifest itself within any period of self-experimentation. This is why anecdotes are useless when evaluating risk.

For example, my grandfather smoked two packs of cigarettes a day for over sixty years, dying in his 80s of a non-smoking-related illness…but that doesn’t change the fact that smokers contract lung cancer 15-20x more often than non-smokers (Thun et.al. 2008), and also suffer from all types of heart disease, many other cancers, renal damage, and impotence at a far greater rate than non-smokers. And while I’ve spent plenty of time making fun of weak associations extracted from known-bad data, I do find the evidence for negative health effects from regular smoking reasonably convincing—though perhaps of smaller magnitude than claimed by typical sound-bites.

In conclusion, it’s clear that anti-nutritionism makes it easy to fall into the trap of extrapolating N=1 beyond its limits. By assuming that we already know all the important anti-nutrients, we can easily convince ourselves that a clearly Neolithic food is healthy (or, at least, harmless) just because we don’t feel any obvious harmful effects from consuming it in the short term.

To answer such questions, we need to apply science, not N=1…

…and it is very likely that the answer will not be authoritative. Scientific answers are much more likely to be of the form “There are a lot of potential toxins, but we don’t know how bad they are for humans, either singly or in combination” or “It’s analogous to something that quickly causes pancreatic cancer in rats—at 10 times a realistic dietary dose.”

That’s where evolutionary context comes in, and where I use my general rule of thumb, previously seen here:

Eat foods you could pick, dig, or spear. Mostly spear.

The Takeaways: Now What?

My intent is not to encourage anyone to become overly fearful about eating the occasional bowl of ice cream or tarka dal! I understand that even functional paleo can feel somewhat limiting at times, and that nothing will make a fresh, hot Krispy Kreme not taste delicious.

What I’m doing is cautioning my readers that no interesting or useful information comes from arguments about whose N=1 is more authoritative; I’m reiterating my own commitment to careful, rational inquiry; and, most importantly, I’m hoping to communicate my own respect, humility, and awe as one infinitesimal part of our huge, beautiful and dizzyingly complex world and the multi-billion year history of life upon it. As I said nearly a year ago:

“There is an important difference between “We don’t know all the answers yet” and “Do what feels right, man.” These questions have answers, because humans have biochemistry, and we should do our best to find them and live by the results.”

The Paleo Identity Crisis: What Is The Paleo Diet, Anyway?

Meanwhile, I will continue to do my best to find interesting and useful information at the intersection of biochemistry and evolutionary context, and I will continue to explain it as best I can to you, my readers, here at gnolls.org.

And since I like to leave my readers with a few practical takeaways, here are some useful thoughts for when you start finding even functional paleo limiting or monotonous.

  • Consider what you’ve gained, not just what you’ve lost. Sure, you can’t just binge on half a dozen crullers anymore…but you can eat all the prime rib you want without any form of guilt. How cool is that?
  • If you’re stuck in a rut of monotonous food, try some new recipes. Yes, it’ll take some time and several tries to find and perfect a new dish you like as much as your current favorites. Here’s an endless source to get you started.
  • Cheat proudly. For the most part, the dose makes the poison…so unless cheating will start you on a binge, it’s better to say “I am going to eat these street tacos because they’re delicious and I want some” than to try to convince yourself that corn is paleo.
  • Cheat intelligently. Think of a cheat as dessert: once you’ve satisfied yourself with a complete meal, you can think about a Coke or a Reese’s. Otherwise you run the risk of your cheat replacing an entire meal—and once you’ve been paleo for a while, 1200 calories worth of Krispy Kremes will most likely make you feel like you’ve contracted Ebola Zaire.
  • Live in your body. The pleasure of junk food lasts until it slides down your throat: the pleasure of good health manifests itself 24/7 in better sleep, less pain, greater mental clarity and capacity, and greater physical ability. The strong, sleek, healthy body of an apex predator is a great place to be. Instead of medicating it into passivity or becoming a sessile peripheral to your computer and television, go outside. Climb a tree, kick balls, shoot baskets. Learn a new skill. Explore somewhere you’ve never been.

    There’s a big, bright, beautiful world out there: what are you waiting for?

Atop a Sierra peak that shall remain nameless

Live in freedom, live in beauty.


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