Unlike wheat, corn, and sugar, legumes aren’t generally associated with “junk food” or processed food products. It’s easy to conjure up hyperbolic images of Twinkies and Wonderbread to demonize wheat, but lentil soup and hummus just don’t have the same effect. Some legumes, like soy, are even widely considered to be health foods, and marketed as nutritionally superior alternatives to animal products. But that doesn’t make them optimal foods for human beings – just because you can’t find them at McDonald’s doesn’t make them healthy.

Phytic Acid

Like grains and pseudograins, legumes contain phytic acid. Phytic acid binds to nutrients in the food, preventing you from absorbing them. It doesn’t steal any nutrients that are already in your body, but it does make that bowl of lentils a lot less nutrient-dense than the Nutrition Facts panel would have you believe. For this reason, it’s usually cited as a major downside of these foods, but the truth is clearly little more complicated, because some Paleo-acceptable foods like nuts also contain relatively high amounts of it. Per unit of mass, most nuts actually have a little more phytic acid than most grains and beans. So why are nuts fine to eat, but lentils are problematic?

Rather than labeling any amount of phytates as harmful, it’s more precise to say that the effects on the body depend on how much you eat. In fact, phytic acid may even have some health benefits in small amounts, so it’s not accurate to dismiss it as nothing but a toxin to avoid. The key is in how much you eat: this is why nuts are fine in moderation, while legumes and beans are discouraged. The difference is that nuts and kale aren’t staple foods in most people’s diets – if you were relying on almonds as a chief source of nutrition, which hopefully you aren’t, you’d suffer from the same problems.

Beans and legumes, unlike nuts and vegetables, are the primary source of calories for many people around the world, and eating foods so rich in phytic acid as nutritional staples is quite unhealthy. If you replace meat and animal fat with soy and lentils, you’re drastically decreasing your nutrient intake – these plant proteins are less nutrient-dense in the first place, the phytic acid prevents your body from getting even the nutrients they do contain, and unless you eat them with another source of fat, the lack of dietary fat will also stop your body from absorbing and using them. Thus, basing your diet on these foods can lead to severe nutritional deficiencies. In terms of phytic acid content, eating a handful of lentils as a snack every now and again probably wouldn’t be any more problematic than eating a handful of cashews, but that’s just not the way people eat lentils.

Other problems with beans and legumes

In addition to their phytic acid content, legumes are also FODMAPS, meaning that they contain a type of carbohydrate called galaco-ligosaccharides that can cause unpleasant digestive problems for some people, especially people who already have IBS or similar digestive problems. This isn’t necessarily a reason for anyone else to avoid them (any more than you would avoid other FODMAPS foods like onions or mushrooms if you aren’t sensitive to them), but it’s definitely a concern for anyone with pre-existing digestive troubles.

Another drawback of these foods is their lectin content. Lectins are proteins found in almost all kinds of foods, but not all lectins are problematic. Different people react to different lectins, which is why, for example, some people are fine with eating members of the nightshade family, and other people react to them. Potentially toxic lectins are highest in grains, legumes, and dairy. In the body, lectins damage the intestinal wall, contributing to leaky gut, with all its associated digestive and autoimmune problems. While many lectins can be destroyed by proper preparation methods (more on this below), most people find these cooking methods irritatingly laborious, and it’s almost certain that any beans or legumes you buy in a restaurant won’t be cooked this way. Thus, making beans and legumes a regular feature in your diet can significantly contribute to gut irritation and permeability.

Anyone trying a lower-carbohydrate version of Paleo should also beware the carb content of many beans and legumes: vegetarians might tout them as a “protein source,” but this is only really true relative to foods like bread and vegetables, which have no protein at all. One cup of black beans, for example, has approximately 230 calories, with around 170 of those being from carbs. Only around 53 of the calories in this “protein source” are actually from protein. While there isn’t anything wrong with the inclusion of safe starches in the diet, eating beans as a staple source of calories will quickly deliver many more carbohydrates than your body needs. In the long term, this can contribute to weight gain and metabolic problems like insulin resistance.

Beans and legumes also don’t have much to make up for this: they can’t match the micronutrient content of animal foods, so there isn’t any compelling reason why we should eat them. If chickpeas or kidney beans were extremely high in some vital and rare nutrient, they might be worth eating once in a while as a kind of supplement food, but the reality is that they don’t have anything you can’t get in a more potent and healthier way from animals or vegetables. Vegetarians love them for the protein, but on a Paleo diet, you have plenty of better protein options: you don’t need to rely on rice and beans.

Special case: Peanuts

Peanuts are probably the sneakiest type of legumes, if only because of their name. Like other legumes, peanuts are problematic because they contain lectins and phytic acid, but peanuts also bring a new guest to the party: aflatoxins. Aflatoxins aren’t actually part of the peanut itself; they’re produced by a mold that tends to grow on peanuts (as well as other non-Paleo crops like corn). This mold thrives on crops stored in warm, humid places, and it’s so difficult to eliminate that the FDA has declared it an “unavoidable contaminant.” Organic or all-natural brands of peanuts and peanut butter aren’t any better, since the peanuts still have to be stored and transported. Unless you’re picking your peanuts directly from the farm, you’re probably getting some aflatoxins with them, and they’re not something you want: some research has linked long-term consumption to aflatoxins with risk for diseases like cancer and hepatitis B, especially in countries where peanuts are a staple food. Especially in people with mold sensitivities, peanuts are a particularly concerning type of legume.

Unlike many other types of lectins, peanut lectins are also very difficult to destroy by cooking. As discussed further below, proper cooking methods can destroy many of these sneaky gut irritants, but peanut lectins are very heat resistant, so roasting or otherwise cooking the nuts doesn’t help.

Special case: Soy

Another type of legume that deserves special mention is soy. Some vegans seem to subsist entirely on soy products – soy milk with their cereal in the morning, edamame salad for lunch, and tofu stir-fry for dinner. Soy is beloved by the modern diet industry because it’s cheap to grow and incredibly easy to flavor and process into almost anything. But in the long run such a “cheap” crop comes at a steep price: the health of the soil it grows in. And the “convenient” additive suddenly starts looking a lot less appetizing when you understand the health costs of eating it.

As well as the same lectins and phytic acid as other legumes, soy has one particular nasty downside: phytoestrogens. Like environmental estrogens, these chemicals mimic the action of estrogen in the body. The problem with this is that their imitation of estrogen only goes far enough to trick your body into thinking that’s what they are. They don’t actually perform any of the vital functions that real estrogen does. The exact mechanisms by which they do this are very complex, but the upshot is that they tend to produce hormonal problems because they tell your body it has enough estrogen, even though it actually doesn’t.

In men, this hormonal imbalance can cause the development of typically “feminine” traits like breasts and fat deposits on the hips; in women, it can impair fertility and lead to all kinds of menstrual and other reproductive problems. Most alarmingly, phytoestrogens have been linked to breast cancer and disruption of normal thyroid function. It’s not necessary to be alarmist (eating soy products alone is unlikely to cause extreme problems), but in the context of a world full of other environmental estrogens and hormone-disrupting chemicals, soy adds one more straw to the camel’s back – and unlike many environmental pollutants, it’s a straw that’s completely avoidable.

As well as hormones, soy also contains trypsin inhibitors, which interfere with protein digestion, and it increases the body’s needs for several important micronutrients, including Vitamin B12 and Vitamin D. Soy protein powder is even worse: this is a completely processed, artificial non-food that shouldn’t be part of anybody’s diet. Skip the post-workout shake and boil yourself up a few eggs or grab a can of sardines instead: there’s no reason why anyone needs to gulp down a massive dose of processed soy product every day, and there are plenty of reasons not to.

Of course, any argument that soy is unhealthy tends to raise the “Asian objection:” if people in Asia are so much healthier and longer-lived than Americans, and they eat a lot of soy, how could it be so bad? One difference is that traditional Asian cuisine relies much more on fermented foods: as described below, it’s possible to make legumes much more digestible and less harmful by fermenting them. Also, the soy products eaten as part of traditional meals were not industrially processed, and were served in addition to a very nutrient-rich diet that also includes lots of organ meats, bone broth, and vegetables. There is a world of difference between a small amount of fermented tofu in a big bowl of broth and a huge scoop of soy protein isolate in a protein shake full of food coloring and sugar.

Tofu and soy milk are easy enough to avoid (who wants to eat tofu when they could eat real meat instead?), but one soy product poses a particular challenge on Paleo: soy lecithin. This particular form of soy is an ingredient in most brands of dark chocolate, a common Paleo indulgence. Soy lecithin is actually a byproduct of the production of soy oil, and it’s not any better than any other kind of soy. In a moderate serving of chocolate, the dose of soy lecithin is small enough that some people might not have any problems tolerating it, but it isn’t doing anyone any favors, and it’s not difficult to find a brand of chocolate without it.

Sneaky legumes: Soy and peanut oils

One way that many people ingest beans and legumes (sometimes without even being aware of what they’re eating) is through oils. Peanut oil (a staple in many Asian restaurants), soybean oil, and other similar vegetable oils are very common cooking ingredients, on the mistaken belief that since they don’t contain animal fat, they must somehow be “heart-healthy.” But these seed oils might be even worse for you than the plants they come from. Even naturally produced seed oils contain high levels of PUFAs and Omega-6 fatty acids, both of which are inflammatory. Since PUFAs are very unstable fats, these oils can easily oxidize, a process that produces harmful molecules called free radicals. When you cook with the oil, this process accelerates, producing even more. These free radicals are a major driver in inflammation and oxidative stress, the main culprit behind aging and many chronic degenerative diseases.

Even if you don’t buy or cook with vegetable oil, you can still get it if you buy peanut butter. If you’ve ever brought home a jar of all-natural PB, you’ve probably noticed how the oil floats to the top of the jar, requiring you to stir it before you dig in. When you stir that oil back into the peanut butter, you’re loading down your afternoon snack with an extra dose of rancid oxidized fats. This is actually why some people prefer to also pour the oil off the top of jars of almond butter: to get a creamier texture, they just add in healthier saturated fats like coconut oil. In general, nut butters aren’t an ideal food because they make it very easy to overindulge, but if you enjoy them, swapping out the PUFAs for saturated fats is always a more nutritious choice.

Peanut oil is bad enough even though it’s the product of a fairly simple procedure. Soybean oil is even more concerning because of the way it’s processed. From start to finish, soybean oil is a product of modern monoculture farming. Socrates and Plato could sit down to olive oil at dinner time, but soy oil would have been a completely foreign concept to them because the technology for making it simply didn’t exist. To produce this particular food product, the oil company first extracts the oil from the beans using a chemical called hexane, a byproduct of the process that refines crude oil into gasoline. If that isn’t unappetizing enough, the beans are then washed and purified with various other chemical solutions, heated to very high temperatures in the process, and then bleached to remove unwanted color and smells.

For products like margarine, which need to be solid rather than liquid, the soy is then hydrogenated. Hydrogenation solidifies the oil by pushing bubbles of hydrogen through it. This changes the oil from a liquid to a solid by changing the fats from naturally occurring PUFA to something even worse: artificial trans fats. These industrial trans fats should not be confused with the trans fats that are naturally found in animal products: nobody is putting trans fat in beef by forcing hydrogen bubbles through a cow! While naturally occurring trans fats are perfectly healthy, the industrial Frankenstein foods are not. The body can’t make heads or tails of these artificial fats, so they’re highly inflammatory, and contribute to all kinds of problems as diverse as weight gain, atherosclerosis, and infertility.

Soaking, sprouting, cooking, and fermenting

As with pseudograins, you may be able to make beans and legumes much more digestible by preparing them in various traditional ways. This is one reason why Asian cultures see fewer ill-effects from eating traditional foods like natto: proper preparation (as opposed to industrial processing) can make these foods much less problematic. This obviously depends on your level of tolerance for them – and peanuts and soy should still be avoided no matter what cooking method you use – but it’s useful to understand how you can at least minimize the danger from these foods.

Many traditional cooking methods go quite a long way in reducing phytic acid content, for example. Soaking is a good first step – it can help reduce some of the phytic acid but doesn’t completely eliminate it. Sprouting is the most effective method for legumes, reducing phytic acid by 25 to 75 percent. The process of sprouting a batch of beans or legumes is actually fairly easy: all you really need to do is keep them moist and give them access to the air. Fermentation also greatly reduces the phytic acid of many different types of food – and it gives your gut flora a boost as a bonus. Note that the phytic acid in soy is particularly hard to reduce: this is another reason to avoid it if at all possible.

After any soaking or fermentation, you still have to cook your legumes before you can eat them – this adds another layer of protection because heating most beans and legumes (with the exception of peanuts, which have lectins that survive the cooking process) will destroy most of the lectins in them. Since nobody eats raw beans or legumes, this significantly reduces the concern about their lectin content.

These traditional methods of cooking won’t turn lentils or beans into a magical health food. But if you do need to eat them for some reason, they can help reduce their more dangerous aspects. Paleo isn’t about perfection, so if you have to stretch $20 into grocery money for the week, a few bags of lentils or black beans, properly prepared, will do a lot less damage than ramen and peanut butter.

If it looks like a bean and it sounds like a bean…

…it might not be one! In the same way that peanuts aren’t actually nuts, coffee beans, cocoa beans, and vanilla beans aren’t actually beans. Coffee can be problematic for some people for other reasons, but it’s actually a seed, not a bean. Vanilla and vanilla bean extract are also fine, as are cocoa products. Of course, if you react poorly to these foods for other reasons, there’s no reason to include them in your diet, but there’s also no reason to deprive yourself of them because you’re worried about the dangers of legumes.

Green beans are also somewhat of a special case. When we eat green beans and similar vegetables like snow peas, we eat the pod with the seeds – the seed contains the vast majority of the problematic elements, so a serving of green beans already has much less phytic acid than a serving of soybeans. Also, like nuts, most people don’t eat green beans as a staple food – most of us might have a serving once a week or so, but we don’t rely on them as a major source of energy. Since they contain comparatively fewer problematic elements, and since they aren’t a major component of anyone’s diet, green beans are often regarded as an acceptable Paleo side dish, just like nuts. If you’re very sensitive, you might need to eliminate them, but most people can eat them once in a while without worrying about it.

Conclusion

In conclusion, the main problem with most beans and legumes might be negative, rather than positive: when eaten as a staple food, they simply crowd out more nutritious foods like animal products. Combined with the phytic acid and lack of fats in the legumes themselves, this can lead to a perfect storm of nutritional deficiency. Peanuts (which contain aflatoxins and heat-resistant lectins) and soy (which contains phytoestrogens) are particularly problematic; these are definitely foods to avoid strictly. Other legumes might not cause such serious problems, but that doesn’t make them good staple foods for a healthy lifestyle: a diet based on high-quality animal foods is much more nutritious without requiring all the annoying and time-consuming preparation of soaking, sprouting, and fermenting – and it tastes better.

If you were used to eating a fairly healthy diet before they switched to Paleo, you might occasionally miss your lentil soup or hummus. After properly preparing the lentils or chickpeas, a small amount of these foods probably won’t do a lot of damage, but think of it as an occasional indulgence rather than a dietary staple. Alternatively, you could try more Paleo-friendly recipes like baba ghanoush or a thick, hearty “lentil” soup (this recipe uses cauliflower and plenty of spices to get the same texture). Experimenting with these new recipes is a great way to brush up on your cooking skills and enjoy making something tasty without the digestive stress of eating unhealthy foods.