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10 Reasons to Avoid Eating Legumes

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Paleo why legumes are badHave you ever stopped to reflect on the ways that we talk about beans?

Take the most famous beans in history, for example…

Young Jack was on his way to town to sell his family’s only cow, when a stranger talked him into trading the cow for a handful of “magic” beans. When Jack got back home, his mother was so furious about having only the worthless beans, that she threw them out the window. (The rest of that story took a more fantastic twist, of course.)

And even today, you might off-handedly note that something isn’t worth a “hill of beans,” indicating that it’s practically worthless.

However, if you spend 2 minutes on Google right now, you can find hundreds of articles about the health virtues of beans. Many sites praise their nutritional value, their high-fiber content, their ability to help prevent cancer, and even the amount of protein you can get from legumes.

They’re such darlings in the vegetarian and vegan world that you might think beans actually lead to bags of gold, golden-egg-laying hens, and magical harps.

And yet, you’re Paleo. You avoid legumes at all costs. Are you missing out???

First of All, What is a Legume???

To over-generalize, a legumes is a bean, pea, lentil, or peanut.

To get a bit more specific, here’s a list of the most common legumes (check out this site if you want a really comprehensive list):

Paleo why beans are badblack bean
Boston bean
chili bean
fava bean
field pea
frijole negro
green beans
green and yellow peas
kidney beanpaleo why beans are bad
lima bean
Mexican black bean
Mexican red bean
mung bean
pinto bean
red bean
small white bean
split peas
soy bean (read this article for soy specific issues)

Should You Eat Legumes?

Most Paleo folk steer clear of legumes, but do you really know why?

While I don’t think legumes are the worst thing you can eat – things like pizza, milkshakes, and donuts are far worse – here are 10 reasons to avoid legumes:

1. Legumes are Low in Nutritional Value

Proponents of legumes list nutritional values that are based almost entirely on the legume in its raw state, but once a legume is cooked, it loses much (though not all) of its nutritional value.

Legumes are often praised for being a great source of protein, and while they do contain a decent amount, they’re still nowhere near as good as most animal sources, particularly when you account for the quality of the protein.

Legumes are also often high in iron, magnesium, potassium, and calcium. Unfortunately, these are the primary minerals that don’t get absorbed due to high phytate levels (see #2 below).

The Takeaway is that legumes have some nutritional value, but they are not providing you anything that you can’t get more easily and better from other foods.

2. Legumes Contain Phytates

Paleo why beans are badPhytates – for the most part – just prevent minerals in a particular food from being absorbed. They’re not stealing minerals out of your body.

Phytates are not a major concern on their own. But if you’re planning on eating beans or lentils as a large portion of your diet, then it’s worth knowing that you’re not actually absorbing a lot of the minerals. This is particularly important if you’re considering replacing meat and animal fat with legumes, since meat and animal fats are some of the most nutritious foods you can eat.

In addition, phytates also inhibit the functioning of certain enzymes that are critical to digestion, such as pepsin and amylase. This explained a bit more in point #4 below. For a really thorough discussion of phytates, see this Weston A. Price Foundation article.

3. Legumes Contain Lectins

paleo stomachLectins are a class of proteins that plants produce partially in order to protect themselves from predators. (You can read more about lectins here.) Some lectins (such as Wheat-Germ-Agglutinin – found primarily in wheat) are terrible and definitely cause problems.

The 2 main effects of lectins are that they cause “Leaky Gut” and they lead to increased inflammation in your gut.

Both of these things may not cause any immediate problems when you eat lectins, but they often lead long-term to all sorts of problems, such as not being able to properly absorb vitamins and minerals, food allergies, arthritis, and a variety of other issues. Here’s a post from Sarah Ballantyne that explains more.

Some of the most well-known lectins are Peanut Agglutinin, Phytohaemagglutinin, and Ricin, all of which are found in legumes such as peanuts, kidney beans, and castor beans.

Now, most lectins are deactivated by heat, meaning that when you cook these foods, most of the lectins become harmless. There are exceptions to this (including both Wheat Germ Agglutinin and Peanut Agglutinin), but this is one of the main reasons that lectins are not as big of a problem as some people make them out to be.

Still, it’s something to consider. In particular, if you have any existing gut issues (IBS, for instance) or any auto-immune conditions (like Crohns or Hashimotos), then lectins are probably going to be far more problematic for you.

4. Legumes are High in Protease Inhibitors

Proteases are enzymes that break down proteins. So Protease Inhibitors are molecules that stop proteases from doing their job.

In your body, because protease inhibitors keep proteins from being properly broken down and absorbed, your body starts producing too much of certain enzymes. When this happens, it can lead to all sorts of problems like Leaky Gut, chronic inflammation, and allergic reactions.

Soy is particularly bad about this, but most legumes are quite high in protease inhibitors.

5. Legumes Have Carbs and Can Stall Weight Loss

I don’t think that carbs are necessarily “bad” for you.

That said, many of us have damaged our bodies and our metabolisms through decades of eating crap and not moving around very much.

If you are such a person – particularly if you are overweight, or worse, have Diabetes – then carbs are probably not your friend the way that they might be for someone who is healthy and not metabolically damaged.

Legumes – although they have more protein and fiber than most highly processed junk food like potato chips or cookies, still have quite a few carbs.

This is probably one of the last reasons that most people should avoid legumes (after all, they’re not really doing very much for you to begin with), but if you need to lose weight or control your blood sugar, then cutting legumes out of your diet can help immensely.

6. Legumes Can Contain PhytoEstrogens

Paleo why beans are badPhyto means “plant,” and you generally know what estrogen is. So it’s not too difficult to figure out what a phytoestrogen might be.

Phytoestrogens are not actually estrogen, but they act like estrogen. Inside your body, phytoestrogens bind to the same receptors that estrogen binds to, but phytoestrogens give a much weaker signal than estrogen. Because the signals are weak, your body will often over-produce estrogen, which will disrupt your entire hormonal system.

This can lead to a variety of problems, such as disrupted reproduction and infertility, bladder cancer, asthma, and increased incidence of Alzheimers.

7. Cans of Legumes Contain BPA

BPA is a chemcial found mostly in plastic. It is strongly associated with heart disease, prostate cancer, breast cancer, miscarriage, erectile dysfunction, and abnormal reproductive development in children.

Legumes don’t naturally have BPA, of course, but the lining of many cans contains BPA.

If you’re eating fresh legumes that haven’t been canned, then this isn’t a concern. Also, there are suggestions that BPA may not be so harmful actually (see Chris Kresser’s article here).

8. Legumes have some Protein and Fiber

This is not actually a reason to avoid legumes, but it’s important to know.

Legumes tend to have more protein and more fiber than most other plants. This is particularly important for vegetarians, since protein can be hard to come by. In addition, much of the fiber in beans is soluble, which promotes – rather than disrupts – gut health.

Like I said, there are some positive qualities to legumes.

However, if you’re not vegetarian, the argument for protein is a fairly weak one, since legumes pale in comparison to most animal sources of protein, both in amount and in quality.

In terms of fiber, legumes are a good source, but contrary to popular belief, fiber is not particularly vital to one’s health, and in any case, if you’re eating enough vegetables (and maybe some occasional fruits), you’re going to get your fiber.

9. Legumes Contain Saponins

Legumes are extremely high in saponins. Ok…but what the heck are saponins???

Saponins are compounds that are found in many plants, including most legumes. They have a particular chemical structure that allows them to bind to the surface of your intestinal cells.

Once saponins bind to your intestinal walls, they often cause the cells lining your intestines to either “open up” or else to die. In either case, the effect is a Leaky Gut.

Once that happens, saponins, bacteria, and other things start leaking into your bloodstream. An immediate effect is that saponins start destroying the cell membranes of your red blood cells (as well as leading to general inflammation in your body). After that, all sorts of other bad things start happening.

10. Legumes Contains FODMAPs

FODMAPs are a type of carbohydrates. They’re not a problem for everyone, but for many people, they cause a variety of digestive problems.

Pretty much all legumes contain Galactins, which are a particular type of FODMAP.

If you know or suspect that you have digestive issues like Irritable Bowel Syndrome, then legumes are one of the first things that you should cut out.

Here is a great post from Chris Kresser on FODMAPs, if you want to learn more.

So Should You Eat Legumes??

paleo why beans are bad
Despite all of the possible negative effects that I’ve pointed out, I can’t really say that you should definitively avoid legumes. Aside from peanuts and soy, they’re typically better than grains, and if I were vegetarian, I’d almost certainly eat legumes in order to get more protein.

And yet, I can’t ever imagine recommending legumes as a nutritious part of a healthy diet. There is far too little to gain from eating beans versus the potential for digestive and hormonal side effects.

However, if you are going to eat legumes, then it makes sense to eat them the same way that humans have for about 10,000 years (by soaking and sprouting them).

The process of soaking, sprouting, and/or fermenting can break down many of the lectins and phytates, and if you’re fermenting, you’ll also get some bacteria in there that is very good for your gut.

Personally, I tend to follow the lead of Jack’s mom and toss my beans out the window, hoping that something more magical will come of it. (Cheeky. But true.)

Images: Copyright (c) 123RF Stock Photos.

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  • Emily

    What I don’t understand about this whole idea is the promoting of eating animal flesh rather than a legume, which grows from the ground. Think of all of the harmful effects of eating any non-organic meat and/or dairy products. Here you are picking apart something that grows from the earth, when you could be elaborating on foods that really are horrible for your health – like all non-organic meats and dairy items.

  • John

    LOL…… diet trends…. so dumb

  • yelloww2

    You might want to research protein and cancer, also with all the bad foods you shouldnt eat, beans arent likely on the top of the list

    • jmhendon

      This is probably a useless reply, but let me know if you’d like to discuss any particular cancer research. I’ve read far too many papers on cancer and diet, and while you are correct that beans are nowhere near the top of the list (it’s something I point out in the article above already), my assumption (rightly or wrongly) is that your reference to “protein” is based on a vast misunderstanding of the research. One could make a good argument that the Prolamin class of proteins (found predominantly in grains) are one of the primary contributors to incidence of cancer, and I’d agree, although there are a variety of factors (excess energy intake, micronutrient deficiencies, imbalances of polyunsaturated fats, etc.) that appear to also play significant roles. Unfortunately, much of the reporting of the research has been shoddy at best, often focusing on things like casein – a protein that is linked in vitro and apart from whole foods to cancer but not in vivo or as part of whole foods like raw dairy.

  • yelloww2

    It’s not a useless reply and it amazes me that humans (as a whole) still haven’t figured out our ideal diet. This is a well written article and I don’t want to detract from the research you have put in but I recently read “the China Study” and felt that the Macro type approach to analyzing human diet to be more substantial than analyzing individual nutrients within a food. The China study’ evidence of animal based products and cancer are compelling and recently have me wondering if vegetarians had it right all along… I recently joined cross-fit and they push the Paleo diet there which I have been embracing for over two months and am still learning…

    • jmhendon

      Thanks so much for the reply and the compliment. Very much appreciated. I try not to be dogmatic about very many things. I think that being a vegetarian can be fine and done well (I have a lot of vegetarian friends). However, just based on my own reading and his responses to critiques, I generally feel like T. Colin Campbell is not very nice and also intellectually dishonest in many ways. I think that Denise Minger’s critique (http://rawfoodsos.com/2010/07/07/the-china-study-fact-or-fallac/) is still the best. In the end, you’re still right, either way, about legumes. They most definitely are not at the top of the list of things to worry about.

  • neuruss

    As usual, any idea converted in religion ends up converting idiots in fanatics.
    I agree with most of the paleo diet principles, but I just can’t understand the banning of legumes, and all the reasons exposed sound lame to me, to say the least.

    For every single food group, you will hear thousands of experts in favor and against.
    Red meat is essential vs red meat in cancerous, egg is high in cloaks your arteries vs egg is good for you,etc, etc…

    When Paleo enthusiasts spell their gospel, they usually talk about an hypothetical cave man called “Grok”, and how would he have eaten in those days,and its way of life, etc… meaning that if Grok did it that way, we should do it too, because we sharethe same genes!

    Honestly, I just can’t imagine Grok saying to the starving tribe behind him “Watch out for those beans! They have lectins!!”.

    • jmhendon


      Yours is an excellent point. Pre-agricultural humans who couldn’t find enough food to eat would definitely have eaten anything they found that didn’t cause them to become sick. Not to take away from your point, but with many legumes, although they didn’t know it, the lectins are exactly what would have made them think twice. Raw kidney beans, for instance, will make you incredibly sick.

      Legumes are certainly not the worst things you can eat, and many cultures ate them for thousands of years with no adverse consequences. If you’re going to do it, though, I’d highly recommend soaking overnight, which most people don’t do any longer.

      We shy away from talking about “Grok” because I don’t feel like it advances the discussion very much, although evolutionary biology is necessarily the beginning point of modern nutritional science.

      Also, just because you have people on both sides of an argument, doesn’t mean that one side isn’t wrong. I think you have a great point of view, but my thought would be that just because humans ate a food when they had nothing else to eat does not necessarily mean that it’s optimal. The converse of that is if humans ate a food for millions of years (veggies, meats, seafood, fruits), then the likelihood of harm is very low.

      • neuruss

        I agree.One thing that makes me wonder (and I admit I don’t have an answer) is how much our “genes” are supposed to dictate what we should eat or not.
        2/3 of mankind is lactose intolerant, while most europeans and their descendants consume milk and derived products on a daily basis.
        Is it in our genes, or it’s our feeding habits that make us more tolerant to certain foods?
        Asians are known to be lactose intolerant (except mongols who have been raising horses and drinking their milk for ages).
        However, people of asian origin living in western countries eat exactly what we all eat, with no problem at all. How do we explain that?
        The same goes for amerindians. They are supposed to be lactose intolerant (same example).However, my country (Argentina) has a huge dairy culture and so far, nobody has died (as far as I know…), and there are a lot of people with amerindian genes. So how do we explain that?

        All this makes me believe that the argument about Grok’s genes has many weak points.

        • jmhendon

          Relying solely on genetics does have various weak points, as you pointed out. For instance, when humans first came down from trees onto the savannas, they weren’t “evolved” to scavenge and eat the brains and marrow that they started eating. However, it was highly nutritious and was what permitted the development of larger brains.

          Lactose persistence is interesting because it’s barely a genetic change. The distinction is so minor genetically (to allow for production of lactase into adulthood) that it’s almost an epigenetic shift. The fact that many people of asian origin eat dairy does not mean that there is no problem. Lactose intolerance doesn’t typically cause severe issues, but rather bloating, gas, and mild inflammation. I think you’ll find that those symptoms are pretty common among asian folks who eat dairy.

          In the end, I agree with you that we shouldn’t base what we eat entirely on genetics, but I’d still contend that it’s a very good starting point. For instance, genetically, humans produce zonulin when they eat gluten, which then causes the tight junctions in our epithelial cells to open up, leading to leaky gut, inflammation, auto-immune conditions, etc. It’s a genetic condition of all humans. We don’t usually die off because of it, but it’s not good.

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