Black beans are a healthy addition to both vegetarian and non-vegetarian diets. These nutritious and tasty legumes are available dried or canned, and both types provide the same health benefits. The benefits of beans come from a few different components, including protein, fibre, antioxidants and micronutrients.


Black beans are high in protein, so they are an especially good choice for vegetarians and others with diets low in protein. Even people who eat meat can benefit from the protein in black beans. Unlike animal products, black beans contain only trace amounts of saturated fat and no cholesterol. Black beans and rice are ideal because when they are paired, they provide all of the essential amino acids that you need. These amino acids are used to repair and replace the amino acids in your organs as they are broken down over time.


Eating black beans can boost your iron intake because these legumes contain 3.6 milligrams of iron per cup. Maintaining healthy iron levels is essential for preventing iron-deficiency anemia. Black beans are also a good source of calcium, with 46 milligrams per cup, and of potassium, with 611 milligrams per cup. Calcium is essential for building and maintaining bones, and potassium helps regulate your blood pressure and heart rate. Other micronutrients in black beans include magnesium, folate, zinc and phosphorus.


Black beans are high in fibre, containing 15 grams in a cup of cooked beans. Black beans contain both insoluble fibre, which helps improve digestive-tract functioning and prevents constipation, and soluble fiber, which lowers cholesterol and blood-glucose levels. Women need 21 to 25 grams of fiber daily and men need 30 to 38 grams for optimal health.


It has been found that black beans have more antioxidant activity than other types of beans. The level of antioxidants in black beans is about the same as the levels found in apples, grapes and cranberries. Antioxidants neutralize cell-damaging free radicals and may help lower the risk of heart disease, cancer, and other diseases. However, the actual effects of antioxidants in the human body are still under study.


All legumes, including black beans, contain a compound called phytohenagglutinin, which can be toxic in high amounts. This is a major concern with red kidney beans, which contain such high levels of this compound that the raw or undercooked beans may be toxic when consumed. However, the amount of phytohenagglutinin in black beans is typically much lower than the levels in kidney beans, and reports of toxicity have not been linked to this type of bean. If you still have concerns about phytohenagglutinin, cooking beans thoroughly breaks down the toxin and lowers the levels in the beans. It is recommended to boil beans for a minimum of 10 minutes before consuming them. Also recommend against cooking dried beans in a slow cooker because these devices typically cook food at temperatures that do not break down phytohenagglutinin and may actually raise the levels of this toxin.

I’ve been cooking black beans for many years and have never gotten sick. But they do need long soaking (12 hours) with a rinse or two. That alone releases toxins.

Then after draining and rinsing, bring the beans to a boil and skim the foam before covering and simmering until tender.

The beans will stay at boiling point for long enough that you will meet the minimum boiling recommendations.

* The toxic compound phytohaemagglutinin, a lectin, is present in many common bean varieties, but is especially concentrated in red kidney beans. White kidney beans contain about a third as much toxin as the red variety; broad beans (Vicia faba) contain 5 to 10% as much as red kidney beans.

* Phytohaemagglutinin can be deactivated by boiling beans for ten minutes; the ten minutes at boiling point (100 °C (212 °F)) are sufficient to degrade the toxin, but not to cook the beans. For dry beans it’s also recommend an initial soak of at least 5 hours in water which should then be discarded.

* If the beans are cooked at a temperature below boiling (without a preliminary boil), as in a slow cooker, the toxic effect of haemagglutinin is increased: beans cooked at 80 °C (176 °F) are reported to be up to five times as toxic as raw beans. Outbreaks of poisoning have been associated with cooking kidney beans in slow cookers.

* The primary symptoms of phytohaemagglutinin poisoning are nausea, vomiting, and diarrhea. Onset is from one to three hours after consumption of improperly prepared beans, and symptoms typically resolve within a few hours. Consumption of as few as four or five raw, soaked kidney beans can cause symptoms.

* Beans are high in purines, which are metabolized to uric acid. Uric acid is not a toxin as such, but may promote the development or exacerbation of gout. For this reason, people with gout are often advised to limit their consumption of beans.

* I slow cooked beans for many years (including kidney beans), but I always soaked them, and brought them to a full rolling boil before adding them to the slow cooker. My family never got sick, but maybe we were just lucky.

* For the last couple of years, I’ve been cooking all beans in a pressure cooker, which maintains a cooking temperature well above boiling for the cooking time and during the slow pressure release time. Pressure cooking also greatly shortens cooking time.