Black Beans

Health Benefits
(Source: World's Healthiest Foods, George Mateljan)

General Fiber and Protein Benefits from Black Beans

Among all groups of food commonly eaten worldwide, no group has a more health-supportive mix of protein-plus-fiber than legumes. Black beans are no exception. From a single, one-cup serving of black beans you get nearly 15 grams of fiber and over 15 grams of protein. Moreover, black beans rank in our Top 10 foods for fiber and our Top 25 foods for protein. A single one-cup serving of this legume will provide you with 60% of our WHFoods recommended fiber intake and 30% of our WHFoods recommended protein intake. Legumes are the only food group that can provide you with such a strong fiber-protein combination.

Both fiber and protein can help regulate the passage of food through our digestive tract and can help steady the flow of digestion. This steadied digestive flow can result in benefits for regulation of blood sugar and overall digestive tract health. However, as we will see in the upcoming paragraphs of this Health Benefits section, both the fiber and the protein in black beans have special qualities not present in all fibers or all proteins and these special qualities add even greater potential to the unique health benefits provided by black bean proteins and black bean fibers.

Specific Fiber and Protein Benefits from Black Beans

It's not only the impressive total amount of fiber in black beans (about 15 grams in a one cup serving) or the total amount of black bean protein (also close to 15 grams per one cup serving) that provides us with health benefits. It's also the specific type of fiber and protein that we get from this legume that has excited health researchers. On the fiber front, scientists have determined that black beans are a valuable source of resistant starch. The one-cup serving of black beans on our website provide about 41 grams of total carbs, and about 15 of these grams are classified as fiber. If these 15 grams of fiber are subtracted from the total carb amount, we still end up with a lot of carbs—about 26 grams—and included in these 26 grams is a large amount of starch. Ordinarily, this high starch content would raise the glycemic index value for a food and make them a food of concern in terms of their blood sugar and insulin impact. However, in the case of black beans, these concerns are not raised because a large amount of the starch in black beans fits into a category called "resistant starch." Like this name suggestions, much of the starch in black beans is not broken down in our upper digestive tract because it "resists" digestion. In the absence of this starch breakdown, we don't get an increase in simple sugars (the breakdown products of starch) and so our blood sugar level isn't hit with an unwanted degree of increase. Similarly, our insulin response can also stay moderate. It's the resistant starch content of black beans that provides them with a value of "low" on the glycemic index.

In addition to these upper digestive tract benefits, we also get black bean benefits in our lower digestive tract. When the resistant starch in black beans finally reaches our large intestine, it gets broken down by bacteria and provides an increased fuel supply for the cells of our large intestine in the form of short chain fatty acids, or SCFAs. The great likelihood is for these combined digestive tract benefits to eventually translate in reduced risk of colorectal cancer in individual who regularly consume black beans and other legumes.

On the protein front, recent studies show black beans to contain unique peptide components (small sequences of amino acids that are used to form proteins) that further improve regulation of blood sugar and insulin levels. Most of these unique peptides consist of 5-6 amino acids, and they act to inhibit the production of glucose transport molecules like GLUT-2. By interfering with GLUT-2 production, these black bean peptides can help lower glucose absorption from the digestive tract and thereby help steady blood sugar levels.

Unique Phytonutrient Support from Black Beans

Many people assume that black beans are nowhere close to vegetables and fruits in terms of their phytonutrient content. But there are areas in which black beans supply us with important amounts of phytonutrients. Myricetin, quercetin, and kaempferol are among the flavonoids provided by this legume, along with phenolic acids like hydroxycinnamic acid, ferulic acid, sinapic acid, and chlorogenic acid. Saponins like soyasaponin and phaseoside I are also included among the black bean phytonutrients. (Saponins are a subgroup in the larger phytonutrient category known as triperpenoids.) The outer surface of blacks beans—called their "seed coat"—is the most concentrated location for many of these phytonutrients. Particularly important in the seed coat of black beans are its anthocyanins. This flavonoid subgroup is largely responsible for the deep black color that is so striking in this legume. The chart below shows how some of the key anthocyanins in black beans compare in quantity to key anthocyanins found in other anthocyanin-rich foods.

Anthocyanin Content of Black Beans and Other Foods

(milligrams per 100 grams of food)

AnthocyaninBlueberriesRed CabbageRed OnionsBlack BeansMalvidin67.60010.6Delphinidin35.404.318.5Pelargonidin00trace0Peonidin002.10Petunidin31.50015.4Cyanidin8.5209.83.20

Source: Bhagway S, Haytowitz DB, and Holden JM. (2014). USDA Database for the Flavonoid Content of Selected Foods. Release 3.1. Nutrient Data Laboratory, Beltsville Human Nutrition Research Center, Agricultural Research Service, U.S. Department of Agriculture (USDA), Beltsville, Maryland.

As you can see in the above chart, the total quantity of anthocyanins in black beans is not as high as the total quantity in blueberries or red cabbage, yet it is still substantial and includes a variety of different anthocyanins.

The key take-away here is to think about black beans as a food that provides us with valuable phytonutrient support, including the anthocyanin support that we typically associate with fruits and vegetables.

Other Health Benefits from Black Beans

For beans and legumes as a whole (including all types of dried beans and dried peas), research shows potential health benefits in two key areas: (1) cardiovascular diseases, and (2) blood sugar problems, including type 2 diabetes. Reduced risk of all of the following cardiovascular diseases has been associated with overall bean and legume intake: coronary heart disease, ischemic heart disease, hypercholesterolemia, and atherosclerosis. And in addition to type 2 diabetes, better glucose tolerance and improved insulin sensitivity have both been connected to bean and legume intake. Specifically, for black beans, we have also seen several studies showing improvement in multiple lab indicators for metabolic syndrome, including lab values related to blood fat levels and blood sugar levels.

The relationship between black bean intake and risk of cancer is not as well documented as the other chronic disease relationships described above. In animal and lab studies, black bean extracts have been associated with decreased inflammation in the colon and lower risk of colitis, and studies point in the direction of the possibility of reduced colon cancer risk following routine intake of black beans. Also, worth noting in the context of colon cancer prevention are the general anti-inflammatory properties of black bean flours in animal studies. Mice fed this form of black beans have shown increased levels of anti-inflammatory messaging molecules in their blood including interleukin 10 (IL-10) as well as decreased levels of pro-inflammatory messaging molecules including interleukins 6, 9, and 17a (IL-6, IL-9, and IL-17a) as well as interferon gamma (IFN-gamma). These anti-inflammatory effects may turn out to be important for management of cancer risk, since the development of certain cancers may start out with underlying conditions of chronic inflammation and chronic oxidative stress. Still, it is important to remember that large-scale human studies in this cancer area have yet to be undertaken with a specific focus on black beans.

The American Heart Association estimates that approximately one-third of all U.S. adults have a set of chronic disease risk factors called Metabolic Syndrome. These risk factors include high blood sugar, high blood pressure, low blood levels of protective HDL cholesterol, high blood levels of triglycerides, and excess body fat around the waist. When taken as a group, this set of conditions associates with increases in our risk of type 2 diabetes, stroke, and several types of heart disease. In a recent study on a very small group of adults previously diagnosed with Metabolic Syndrome, researchers found that daily inclusion of soup that had been reconstituted from dried black beans helped steady blood sugar and insulin levels. Specifically, insulin secretion following consumption of black bean soup was decreased in comparison with a matched non-bean soup, as was blood sugar elevation. In addition, antioxidant capacity in the bloodstream was found to increase following consumption of black bean soup. Once again, this very small scale study cannot provide us with conclusive evidence about the role of black bean consumption for improved management of Metabolic Syndrome, but the results seem to be pointing in the direction of potential benefits.

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