To Bean Or Not To Bean, That Is The Question (Legumes, Lectins, and Human Health)
Posted on February 15, 2011
by J.D. Moyer
With apologies to Shakespeare.
These days, many people across the world are wondering if they should eat beans, or not.
Right now, this very minute, there are two powerful, but opposing, dietary trends speeding towards a potentially explosive head-on collision.
On the one side the paleolithic (or “Stone Age“) style of eating, a dietary/lifestyle system that eschews grains, legumes, sugar, and all processed foods in favor of quality meats, poultry, fish, vegetables, fruit, and healthful fats. This is the anti-bean side.
On the other side is the fad-diet du jour, Tim Ferriss’s “slow-carb diet” as described in the bestselling The 4-Hour Body. Ferriss unabashedly recommends legumes. Indeed, he suggests eating beans or lentils with every meal (but forbids grains, fruit, and dairy products — except on the once-per-week “binge day,” during which all foods are allowed).
Ferriss must be acknowledged as a cultural force in his own right; he is a master marketer with legions of supportive blog readers (myself among them). His efforts have propelled both of his books to the #1 spot of the New York Times nonfiction bestsellers list. He has recently appeared on both The View and Dr. Oz pushing his slow-carb diet, sleep gadgets, and anatomically precise better-sex tips.
Especially among the California/Silicon Valley/San Francisco/young techy professional set, 4-Hour Body is extremely influential. Just the other night at Ignite SF, a friend mentioned she was “going home to eat some beans.” When Ferriss says eat beans, people eat beans. Ferriss constitutes the current vanguard of the pro-bean side.
Before we evaluate the evidence for and against legumes, let’s see who all is taking sides:
Tim Ferriss (4-Hour Body)
Dan Buettner (Blue Zone)
Andrew Weil (drweil.com) Pythagoras (Ionian philosopher)
Loren Cordain (The Paleo Diet)
Robb Wolf (The Paleo Solution)
Each link goes to a discussion of the health advocate’s recommendation for or against legumes.
Other health gurus take a more nuanced stance. Mark Sisson, from whom I take my own dietary cues, is generally against eating beans and legumes, but acknowledges possible health benefits from eating nattō (a fermented soybean paste with is extremely high in vitamin K2). PāNu blogger Kurt Harris, M.D., another advocate of the paleolithic diet, suggests eliminating beans but gives it a low priority (#11) on his 12 steps to improving health.
The Evidence Against Beans
Contrary to conventional dietary wisdom, paleo diet advocates say you should NOT eat beans. Why not?
1. Beans are hard to digest (the musical fruit).
Beans that are not properly soaked, drained, boiled, drained-again, and slow-cooked can result in severe digestive stress. Even under the best of circumstances, beans can you make fart more.
2. Beans can aggravate auto-immune diseases.
All legumes (beans, but also tofu, soy-milk, peas, lentils, and peanuts) contain lectins. Some of these lectins are implicated in IBS, Crohn’s disease, arthritis, multiple sclerosis, peptic ulcers, allergies, and Type 2 diabetes.
3. Beans are high in starch and carbohydrates.
Beans are a starchy food, high in carbohydrates. Eating significant amounts of beans may interfere with weight loss.
4. Beans contain estrogen mimics, which can be harmful to health.
Beans, especially soybeans but also fava beans and other beans, contain phytoestrogens — weak estrogen mimics that can interfere with hormone function. Phytoestrogens evolved in plants as a defense mechanism, a way to disrupt the reproductive success of predators. Red clover (a legume) has been shown to disrupt reproduction in animals.
Male infants and toddlers are probably the most vulnerable to the negative effects of a high legume diet, as is discussed in this article by Kaayla Daniel of the Weston Price Foundation. From the article:
Every week I get agonized letters from parents who fed their sons soy infant formula and who report estrogenized boys who are flabby, lethargic, high strung and/or embarrassed by breasts and underdeveloped genitals. These parents want to know, “What can we do now?”
Disturbing. Do not feed your infant soy formula.
5. Beans can shrink your brain.
An even more heinous side-effect of eating soybean products frequently may be brain shrinkage.
Tofu turns your brain to jello.
I kid you not. One study looked at autopsies of nearly 4000 Hawaiian men, and compared brain weight results with dietary habits. The men who had eaten the most tofu and soy had smaller brain sizes and a higher chance (more than double) of developing Alzheimer’s disease. The linked article mentions a possible mechanism; phytic acid in soybeans interferes with vitamin B12 absorption (which is independently associated with brain shrinkage and dementia). In most beans, phytic acid can be greatly reduced by soaking, draining, and boiling, but soybeans retain high amounts even when cooked.
6. Lentils might make you fat.
Tim Ferriss recommends eating generous portions of legumes as a part of his “slow carb” weight loss diet. In The 4-Hour Body he mentions lentils as being one of his favorite legumes.
But can lentils make you fat? There is some evidence that the lentil lectin binds weakly to the insulin receptor, setting cells to “always on” for fat production. That’s Peter J. D’Adamo’s hypothesis in Eat Right For Your Type. Though many of D’Adamo’s ideas are speculative and not supported by the evidence, he should at least be credited with bringing lectins into the public consciousness.
7. Many brands of canned beans have bisphenol A in the can lining.
People who eat beans don’t necessarily have the time or inclination to properly soak them, drain them, boil them, drain them again, and then slow-cook them. Canned beans are the logical alternative to time-consuming preparation.
The problem with canned foods is that the plastic can linings often contain bisphenol A (BPA), a powerful endocrine disruptor. BPA is strongly associated with heart disease, prostate cancer, breast cancer, miscarriage, erectile dysfunction, and abnormal reproductive development in children. We should all be staying away from the stuff. For most people, canned food, soda, and plastic bottles/cups are the main sources of BPA.
Trader Joe’s states that their canned beans are BPA-free (though their canned tomatoes and soups do contain BPA). Eden Organic beans are also BPA-free.
Tim Ferriss's "freak to geek" snapshots from his (pro-bean) book The 4-Hour Body.
The Evidence in Support of Beans
1. Beans are high in protein and fiber.
Not everyone enjoys a high-meat diet. For people who prefer to not consume animal protein at every meal, beans provide a decent amount of protein. Because they’re high in fiber, they’re also quite filling.
2. Beans provide a steady source of glucose for energy.
Consuming high amounts of fructose (the sugar found in fruit, corn syrup, and agave nectar) is associated with gaining belly fat, poor insulin sensitivity, increased risk of heart disease, and higher LDL levels. Table sugar is not exempt — sucrose is half glucose and half fructose.
Ferriss recommends eliminating fructose entirely (except on cheat days), and using legumes as a carbohydrate source. The starch in beans breaks down into glucose. Too much glucose can still make you fat, but the fat will be subcutaneous (under the skin) fat, which isn’t associated with disease as much as abdominal fat.
Ferriss claims his “slow-carb” diet has a high rate of compliance, and that one reason for this is the steady energy provided by legumes. It’s true that switching too quickly to a low-carb diet can result in energy crashes; the body needs a few weeks to adjust to using different kinds of fuel (including dietary fat, stored body fat, glycogen, and even lactic acid).
However, most “carb withdrawal” has nothing to do with blood sugar levels. Except in cases of diabetes, the body regulates blood sugar within a tight range, via insulin and glucagon. Most “carb withdrawal” symptoms are in fact exorphin withdrawal symptoms. Beans, which do not contain food opioids, will not protect you from the aches, fatigue, and flu-like symptoms some people get when giving up wheat and dairy.
3. Beans are high in folate and iron, and have appreciable amounts of magnesium, manganese, copper, selenium, molybdenum, and antioxidants.
Beans are not nutritionally empty. Depending on the legume, beans can provide decent amounts of a few vitamins and many minerals.
Bento with beans -- how could something this cute be bad for you?
As for the anti-nutrients, phytic acid and lectins, most can be soaked/drained and cooked out. If you don’t mind having a frothing bowl of beans on your counter (I do), then you can effectively remove most of the anti-nutrients. Soaking is most effective for getting rid of phytic acid, and boiling is most effective for reducing lectin levels. Do not slow-cook beans without boiling first. Slow cooked kidney beans and red beans (often in the form of chili) lead to dozens of cases of lectin poisoning in the U.S. every year.
4. Beans are associated with reduced risk of colon cancer.
If the evidence holds up, this is a pretty big win for beans. Colorectal cancer is a relatively common, very serious disease (second only to lung cancer in lethality).
One clinical trial that looked at over 2,000 adults with precancerous colon polyps found that those people who ate more beans over a four year period had fewer “advanced” polyps and less cancer. Those that increased fruit and vegetables in their diets, but not beans, did not enjoy the same protective effects.
If eating beans actually does reduce the chance of colorectal cancer, what’s the mechanism? One theory is that the nondigestible carbs in beans are broken down (by gut flora) into the short-chain fatty acid butyrate, which has anti-inflammatory and anticancer properties. Various phytonutrients in beans may act synergystically to prevent cancer in other ways.
One interesting possibility, for which there is strong evidence, is that a lectin in broad beans forces colon cancer cells to differentiate. Could it be that not all lectins are bad?
Beans vs. Meat
I think some members of the “paleo community” are guilty of unsophisticated categorical thinking (meat is GOOD — grains & beans are BAD). Instead of looking at the evidence regarding specific foods and the possible benefits of drawbacks of those foods (from all perspectives, including health effects, ease of preparation, taste and culinary possibilities), they eliminate entire food groups and exalt others.
Bacon bias -- wishing something to be health food does not make it so.
Take bacon, for example. Love for bacon has reached fetishistic heights among paleo bloggers. Mark Sisson and Kurt Harris are both on the pro-bacon bandwagon (otherwise, I agree with 90+% of what both these guys recommend). This salt and nitrite-laden meat-product is delicious, but please don’t try to claim that it’s good for you. Processed meats (including bacon) are implicated in colon cancer and other diseases. While saturated fats are not to be feared, nitrites, and to a lesser extent salt, should be.
Unprocessed red meat may also slightly raise the chance of colon cancer, but the risks are less than those incurred by obesity or lack of exercise. And before you smack me in the face with your copy of The China Study, please read this detailed critique by nutrition blogger Denise Minger.
Maybe the solution is to eat some beans with your bacon.
Beans vs. Fruit
Back to fructose for a minute — Ferriss’s book recommends cutting out all fruit. While it makes sense to limit fructose, let’s consider how many blueberries a person would have to eat to get the same amount of fructose delivered by a regular 12oz can of Coke (36g carbs mostly from HFCS). By my rough calculations, that’s about the same as two cups of blueberries. Three whole grapefruit would also do it. I really don’t see a good reason for not eating half a cup of blueberries or a half grapefruit with breakfast — it’s just not that much fructose, and both fruits are high in vitamins and other phytonutrients. On the other hand, a large banana, or 12oz of orange juice, delivers about as much fructose as the can of soda.
For steady weight-loss, Ferriss may be on to something when he recommends beans over fruit. But you’ll probably get the same benefits if you eat some beans and some less-sweet fruit (tart apples, berries, grapefruit, kiwis, etc.).
The Bottom Line — Who Should Eat Beans
The way I see it, there’s no reason to fear properly cooked beans. There is also no reason to force yourself to eat them.
If you don’t like beans, but still want to avoid colon cancer (who doesn’t?), there are many ways to reduce risk. Stay lean, exercise regularly, don’t eat processed and cured meats, keep your vitamin D levels high, and eat broccoli, cauliflower, and cabbage. Raw sauerkraut may be especially beneficial.
Nobody should eat large amounts of soy, in any form, though tiny cubes of tofu in miso soup won’t hurt you. Red beans and kidney beans are risky unless you know how they’ve been prepared. Canned beans may come with an unwelcome dose of BPA.
Anybody who has Crohn’s, ulcerative colitis, IBS, multiple sclerosis, or arthritis should avoid beans. Lectins can tear up the intestinal lining, causing “leaky gut.” Leaky gut, in turn, leads to autoimmune problems. In terms of lectins, dairy products, grains, peanuts and nightshade vegetables (tomatoes, potatoes, eggplant, peppers), are potentially as problematic as beans.
Beans and lentils aren’t an ideal fat-loss food unless you get lots of exercise, both because of starch content and possible lectin-insulin problems (at least with lentils). But properly prepared (soaked, drained, boiled, and slow-cooked) beans are probably a better choice than bread or bananas.
For many people, one of the joys of the paleo diet is that they don’t have to eat beans (or oatmeal, or any of a long list of bland, boring foods). Conventional wisdom (and Tim Ferriss), push beans as a kind of wonder food, but that’s just not the case. You don’t have to eat beans to achieve vibrant health. Many people, like this woman, respond very well to cutting out both grains and beans, but keeping some fruit in the diet (Mark Sisson’s “primal” diet).
Food Avoidance and The Great Carb Debate
I’m fascinated by how food affects health, but I also just enjoy eating. I hope to never get cancer or heart disease, but chances are very good that something will kill me eventually (ideally it will be something exciting, like a genetically engineered dinosaur, or a falling disco ball, or lightning, or an orgy). Dying from complications due to eating too many lectins, gluten, nitrites, or fructose does not strike me as a good way to go out, so I try to limit my intake of those substances.
I do eat beans once in awhile, usually canned pinto or black beans from Trader Joes, or white butter beans in a salad. If I go out to Mexican food I’ll usually eat some meat and refried beans but skip the tortillas and rice.
Dr. Kurt Harris writes the popular PāNu blog.
I agree with Kurt Harris that consuming some carbs is easier on the body than consuming zero carbs or lots of carbs. Going into ketosis now and then won’t hurt you, but long-term ketosis can deplete calcium and selenium, give you bad breath, cause a metallic taste in the mouth, and lead to mental dullness and sluggishness. It’s easy to stay out of ketosis by consuming some carbs. Wheat products, syrups, desserts, and sweet fruits are not ideal choices. Vegetables, berries, properly cooked beans, and even dark chocolate are good choices. Some rice is probably also fine for people who exercise a great deal.
I find the whole notion of avoiding carbohydrates altogether to be faintly ridiculous … somewhat akin to avoiding nitrogen or carbon. Avoiding a specific class of chemicals, like lectins, makes more sense, but even then you may be throwing out the baby with the bathwater. Some lectins may be good for us.
On the whole, I agree with the premises of the paleolithic diet — we’ll be healthier if we eat high quality meats, poultry, fish, eggs, vegetables, and nuts than if we eat “neolithic” foods (processed foods, sugary desserts, grains and legumes, fruit juice, etc.). What I’m skeptical of is the idea that observing any set of dietary rules strictly will make us healthier. We did, after all, evolve to be adaptable creatures, with a robustly flexible digestive system. We’re more like rats than we are like panda bears (who eat only bamboo), koala bears (who pretty much just eat eucalyptus), or lions (who just eat meat).
On the other hand, I’ve noticed that my enjoyment of food has only increased with a slightly more restrictive diet. The less sugar and fruit I eat, the sweeter all food tastes. Same thing goes for salt. Our palate can quickly adjust to a new “normal.” And since I’ve cut out grains for the most part, I eat a much wider variety of meats and vegetables, mostly cooked in pastured butter. It all tastes damn good. A more restrictive diet doesn’t necessarily correspond to less enjoyment of food.
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