The common bean or kidney bean, Phaseolus vulgaris is one of the most widely and easily grown pulses. It is an economic and nutritious staple of many cultures and virtually found worldwide (Broughton et al., 2003). The bean was first found in the Americas (Central America and Mexico). It gained its name kidney bean, so called because of its resemblance to a kidney. It comes in many shapes and sizes, and colours, from ivory to dark red and even black. Whilst they might look different, all these beans are interchangeable in cuisine. Perhaps the most popular dish to find these beans is when they are added to chilli con carne.
These beans are rich in complex carbohydrates such as resistant starch and dietary fibre but low in fat. They also contain numerous vitamins and minerals, and various peptides and proteins. Look out for their range of polyphenols too (Reynoso-Camacho et al., 2006).
Eating beans generally as part of a balanced diet helps contribute to a healthy lifestyle, reduction in heart disease, cancer reduction, improvement in gut function and in the management of diabetes. There is a general impact in managing various chronic diseases associated with what is termed glycaemic stress (high insulin production and high blood sugar levels) (Hutchins et al., 2012).
Cooking With Kidney Beans
Red kidney beans must be boiled well for at least 20 minutes during their initial cooking as they are poisonous when raw or not cooked properly (Kumar et al., 2013).
Do Not Eat Raw Red Kidney Beans!
Cooking of red kidney beans is necessary to avoid being poisoned by a compound called phytoheamagglutenin. This is a lectin which is destroyed by cooking. It has been an issue for those following raw food and natural food diets where heat processing has been abandoned because of a misguided belief that eating all raw food is wholly safe.
In the early part of December 2020 there was a serious case of poisoning in Denmark that left 45 people very sick. A catering company operating in Copenhagen had used frozen but raw red kidney beans that had come from Turkey, via Sweden. The beans had been cooked but not long enough. Many of those who fell ill had eaten a kidney bean salad.
The symptoms of poisoning were sickness, vomiting and diarrhea within a few hours of eating the beans.
Only one or two beans consumed cause this sickness.
Canned pre-cooked beans are often more easily available than dried varieties. These are a very good choice for cooking with, saving hours of care, but should always be drained and rinsed before use.
Storage Of Kidney Beans
Dried beans last for years if kept in a dry, dark place, safe from pests. Canned cooked beans last as long and should be a basic in every store cupboard.
Of all the nutrients, resistant starch is one of the highest. the average content in raw beans is 24.7% although this is modified when these beans are cooked but the extent of the change depends on the type of processing adopted (Fuentes-Zaragoza et al., 2010).
Bioactive Compounds In Kidney Beans
Anthocyanins: these antioxidants are found in the skin of the bean. The red colour is due to a particular anthocyanin called pelargonidin
Phytic acid (phytate): A common compound in all seeds. It is regarded as a problematic component because it stops the absorption of various minerals including zinc and iron. The best way to reduce the presence of this anti-feeding factor is to soak, ferment and sprout the beans.
Starch Enzyme Inhibitors: Lectins are a class of proteins which inhibit the breakdown of starch by blocking the performance of alpha-amylase. This is a problematic in that it can impair or delay the absorption of carbohydrates in the gut. On the other hand some perceive this as a remedy for diabetes and obesity and further investigation is merited. The lectins are destroyed by cooking and boiling of the beans (Obiro et al., 2008).
Nutrition Of Kidney Beans
Kidney beans are especially valuable in nutrition especially in the developing countries where the availability of animal based proteins is limited. Too many in one go and they cause wind or flatulence. This effect is reduced in two ways:-
(1) By introducing small amounts of kidney beans slowly into your diet, then eating them regularly. The gut eventually adjusts to the load and stops fermenting them as vigorously.
(2) Dried kidney beans must be soaked to hydrate them before cooking. The secret is not to cook them in the water in which they have been soaked but to drain and then rinse them well before putting into fresh water. The soaking water has absorbed much of the ingredient that upsets the gut.
Common beans provide reasonable nutrition levels because they are relatively high in good quality carbohydrates (Sathe and Despande 2003) and proteins (De La Fuente et al., 2011).
A one-cup serving size of cooked kidney beans contains about: (see article).
• 219 calories
• 39.7 grams carbohydrates
• 16.2 grams protein
• 0.2 gram fat
• 16.5 grams fiber (fibre)
• 131 micrograms folate (33 percent DV)
• 5.3 milligrams iron (29 percent DV)
• 0.6 milligram manganese (28 percent DV)
• 0.5 milligram copper (26 percent DV)
• 243 milligrams phosphorus (24 percent DV)
• 742 milligrams potassium (21 percent DV)
• 85.0 milligrams magnesium (21 percent DV)
• 0.2 milligram thiamine (15 percent DV)
• 117 milligrams calcium (12 percent DV)
• 1.5 milligrams zinc (10 percent DV)
• 0.6 milligram vitamin B6 (9 percent DV)
o milligram riboflavin (6 percent DV)
• milligrams niacin (5 percent DV)
• 0.4 milligrams pantothenic acid (4 percent DV)
• 2.1 milligrams vitamin C (4 percent DV)
• 2.1 micrograms selenium (3 percent DV)
The P. vulgaris cultivars are associated with several health benefits (Luna-Vital et al.,2014a, 2014b) such as reduction of risk of diabetes and cardiovascular disease attributed to the presence of polyphenols and bioactive peptides (Xu et al., 2007; Betancur-Ancona et al., 2014).
Lowering Cholesterol And Reducing the Risk Of Cardiovascular Disease
Heart disease is still a major killer and the cause of over a third of all deaths in the western world. Any changes to diet by reducing the number of risk factors helps to minimize heart disease, reduce stroke risk and heart attacks. Diet is one method of achieving a notable reduction in these risk factors, and known more so than eating fibre-rich foods like beans including kidney or common beans (Bazzano et al., 2011).
The study was a meta-analysis of nine studies which totalled 238 subjects (Bazzano et al., 2011). All those who consumed beans of one sort or another showed a reduction in their LDL cholesterol levels and in some cases an improvement in their HDL cholesterol levels. It is understood that the presence of a number of factors in beans generally help alter the cholesterol ratios and improve the excretion of bile acids.
The Dietary Guidelines for Americans suggest we should consume 3 cups of legumes, which are rich in soluble dietary fiber and vegetable protein, per week; however less than a third of the population meets this guideline (Guenther et al., 2006).
Beans contain soluble fibre and we tend to focus on resistant starch here (Fuentes-Zaragoza et al., 2010). Soluble fibre is fermented in the colon of the lower intestine producing short chain fatty acids (SFCAs) such as acetate, propionate and butyrate. These three molecules help decrease cholesterol synthesis by the liver which in turns reduces the production of LDL-cholesterol.
Another benefit is the reduction in inflammation.
Bean hydrolysates and peptides have the ability to inhibit angiotensin I converting enzyme (Luna-Vital et al., 2015). This is another key property in helping to reduce blood pressure (hypertension) and ameliorate the effects of cardiovascular disease.
Beans are always likely to be considered an integral part of any weight loss programme. The presence of plenty of resistant starch in the diet should be considered and the kidney bean may well offer that benefit.
It is known that a continued high blood sugar increases the risk of various chronic diseases including diabetes as well as heart disease. Reducing blood sugar levels especially to reduce the spiking following a meal is generally beneficial for health.
Beans figure greatly in diets which would be part of a blood glucose management programme and hence help with diabetes management. (Hutchins et al., 2012; Jenkins et al., 2012). Beans have a low GI value so the rise in blood glucose levels after a meal means that rise is more gradual and sustained rather than a sharp rise.
Revised from the original of the 23rd January 2015 by adding an important section on food poisoning by raw red kidney beans. Remember to always cook them long enough!
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