Many people eat legumes — like beans and lentils — as a cheap and shelf-stable form of nutrition.
However, it can be tricky to know how to prepare these foods from scratch, and some types of legumes require some advanced preparation in the form of soaking.
Why is it necessary to soak beans before cooking?
The first reason that soaking is a necessary step in cooking dried beans is that this step rehydrates the beans, allowing them to cook more quickly and evenly.
This will allow for the optimal texture of the final product — it means less split-open and burst beans, and an overall softer and smoother texture.
It also reduces cooking time — depending on the type of bean, it may reduce cooking time by up to 75%.
According to food scientist Harold McGhee in this Taste of Home article, you should soak your beans in salted water at a rate of 2 teaspoons per quart of water.
The salt will displace the calcium and magnesium in the cell walls of the bean, causing the outer skins to soften and ultimately allowing for more even cooking.
There is also good reason to believe that soaking beans prior to cooking will be beneficial from a nutritional and digestive perspective.
This is an important consideration, as many people are consuming beans for the nutrition they provide, and beans are also notoriously hard on one’s digestion.
Beans contain antinutrients, such as phytic acid, that inhibit some enzyme processes in the body that are essential for digestion.
For example, phytic acid seems to disrupt the action of enzymes like pepsin (involved in the digestion of protein) and amylase (involved in the digestion of starch).
Phytic acid also interferes with the absorption of the nutrients present in the beans because it binds to minerals like iron and zinc.
However, according to functional medicine practitioner Chris Kresser, soaking beans for 18 hours at room temperature, or for 3 hours at 140 degrees Fahrenheit, eliminates between 30 and 70% of the phytic acid present in the beans.
This could improve both digestion and absorption of nutrients, with the caveat that soaking beans can also potentially degrade the water-soluble vitamins present in the beans (there’s always a trade-off!).
Beans also contain varying amounts of lectins, depending on the type of bean.
There has been some research that shows various negative effects from lectins in animals — effects such as impaired growth and development, damage to intestinal lining, interference with pancreatic function, and damage to skeletal muscle.
However, Kresser points out again that properly preparing beans goes a long way towards neutralizing the effects of lectin.
With lectins, it appears that simply cooking beans prior to eating them, even without the soaking step, almost completely deactivates the lectins in beans.
Finally, beans contain high amounts of FODMAPs — a category of carbohydrate that causes gas, bloating, and other uncomfortable digestive symptoms in many people.
Soaking beans prior to cooking leaches at least some of these gas-producing FODMAPs out of the beans and into the water, potentially reducing some of the negative digestive reactions.
What happens if you don’t soak beans before cooking?
Skipping the soaking step may be problematic from a cooking perspective.
Beans with thicker skins, like black beans or kidney beans, are especially in need of soaking in order to produce even cooking.
If your beans have thinner skins, however, you may safely skip the soaking step or reduce the soaking time without negatively impacting the texture of the cooked beans.
If you don’t soak beans before cooking them, it may also be detrimental from a nutritional or digestive perspective.
As noted above, soaking beans neutralizes some of the potentially harmful compounds in beans, such as phytic acid, lectins, and FODMAPs.
If you skip the soaking step, your body may be impaired in its absorption of the many nutrients present in the meal you’re eating — not just the beans, but also whatever nutrition is present in the other components of the meal, especially the minerals.
You also may be more likely to experience gas or bloating after the meal.
Are beans poisonous if not soaked?
The key principle to keep in mind when thinking about the toxicity of a substance is the phrase, “the dose makes the poison.”
This means that “a substance that contains toxic properties can cause harm only if it occurs in a high enough concentration.” Even water can be toxic if it is consumed in a high enough amount.
With beans, the potentially poisonous or toxic substance to be most concerned about is a type of lectin called phytohaemagglutinin (PHA).
This lectin is present in particularly high amounts in kidney beans, which is why consuming undercooked kidney beans is likely to cause food poisoning.
However, cooking kidney beans for as little as 15 minutes (or half that long in a pressure cooker) almost completely deactivates PHA and therefore almost completely eliminates the risk of food poisoning.
The caveat to this is that slow cooking beans fail to get cooking temperatures high enough to neutralize lectins — this is why there have been instances of food poisoning reported when consuming beans cooked in crockpots.
This is true even of unsoaked beans.
Thoroughly cooking your beans at a high enough temperature (by boiling or pressure cooking) should be your main concern when seeking to avoid food poisoning.
The takeaway from this is that your barebones approach to preparing beans should be to cook them thoroughly, either by boiling or pressure cooking.
You can skip the soaking method if you’re short on time and should not have to worry about food poisoning (soaking is still beneficial if you have time — see the section above).
Can you get sick from undercooked beans?
On one fateful day, the staff was fed a dish that contained kidney beans, which turned out to be undercooked.
Several people then suffered severe vomiting and diarrhea, which lasted for about a day.
Afterward, no pathogens were detected in the food, but it was discovered that the bean dish contained abnormally high amounts of phytohaemagglutinin (PHA), due to being undercooked.
Cases of food poisoning have also occurred from consuming beans cooked in slow cookers.
It appears that slow cookers do not reach sufficiently high cooking temperatures to neutralize the potentially problematic lectins in the beans.
How can you tell if beans are undercooked?
If you do try this method, make sure to spit out the bean if you detect an undercooked or overly firm texture.
You likely won’t get food poisoning from swallowing a single undercooked bean, but it’s better to be safe than sorry.