Red in colour and shaped just like the kidneys of an animal or human, red kidney beans are commonly added to soups, stews, salads and other meals in most countries. You can buy them fresh, canned, or dried, and the nutrition they deliver means they should always be part of a healthy diet.
Nutrition facts of red kidney beans
100 grams (3.5 ounces) of boiled beans contains:
- Water… 67%
- Calories… 127
- Protein… 8.7g (8.7%)
- Fat… 0.5g (0.5%)
Carbohydrates… 22.8g (22.8%) of which;
- Sugar… 0.3g (0.3%)
- Fibre… 6.4g (6.4%)
As you can see, with moderate calories and very small amount of fat and sugar, as well as loads of fibre, these beans are an ideal part of a diet for diabetics. In addition, red kidney beans contain lots of beneficial micronutrients such as folate, iron and manganese.
Protein … these beans are rich in protein. A 100g has nearly 9 grams of protein, which is 27% of the total calorie content.
Carbohydrates… starchy carbs account for about 72% of their total calorie. Bean starch is a slow-release carb (ie, it has a low GI). It causes a lower and more gradual rise in blood glucose compared to other starches. Thus, red kidney beans are especially beneficial for those of us who have type 2 diabetes.
Fibre… these beans are particularly high in fibre, including substantial amounts of resistant starch, a prebiotic. Prebiotics move through you colon until they reach you colon where they are fermented by beneficial bacteria. This fermentation results in the formation of short-chain fatty acids, which may improve the health of your colon and reduce your risk of colon cancer.
Micro-nutrients… the beans are rich in various vitamins and minerals. These include… molybdenum… folate (aka vitamin B6 or folic acid)… iron (but the phytate in these beans may mean that iron is absorbed poorly)… copper… manganese… potassium, and… vitamin K1, which is important for blood coagulation.
Health benefits of eating red kidney beans
By incorporating these beans in your diet, you can experience substantial health benefits. These include:
- Reduced risk of developing type 2 diabetes
- Better control of blood glucose levels
- Protecting cells from damage
- Helping to prevent and treat some cancers
- Reduced risk of obesity
Reduced risk of developing type 2 diabetes… these beans have a much lower GI (glycemic index) than other carb-rich foods, probably due to the fibre and resistant starch they contain. The glycemic index is a measure of the speed with which individual foods increase blood glucose levels after you eat them.
A 4-year study of 3,349 people found that consuming large amounts of legumes and lentils was associated with a lower risk of developing type 2 diabetes. The study also found that eating half a serving of legumes a day instead of a similar sized serving of eggs, bread, rice or baked potatoes was linked to a lower risk of developing diabetes.
It seems obvious that eating red kidney beans instead of other high-carb foods can reduce blood glucose levels in both those who are and who are not type 2 diabetic.
Better control of your blood glucose levels… according to a review published in the American Journal of Clinical Nutrition, adding pulses to your diet, such as beans, could reduce your fasting blood sugar and insulin, thus supporting control of blood glucose in the long-term.
Protecting cells from damage… these beans are a great source of antioxidants, compounds that help neutralise free radicals, thus reducing inflammation and protecting cells from damage and disease. Foods high in antioxidants may also help prevent chronic conditions such as heart disease, cancers and autoimmune disorders.
Improving heart health… research suggests that eating plenty of legumes, such as these beans, as part of a healthy diet can reduce levels of total and LDL (bad) cholesterol, both of which are major risk factors for heart disease.
In addition, other studies have shown that eating legumes can reduce markers of inflammation, many of which contribute to chronic conditions such as heart disease.
Other research indicates that eating plenty of legumes as part of a healthy diet can reduce levels of total and LDL (bad) cholesterol, both of which are major risk factors for heart disease.
Helping to prevent and treat some cancers… eating kidney beans is a good source of flavanols, plant compounds that act as antioxidants. According to a study published in 2009, consuming higher amounts of flavanols is linked to a lower risk of advanced adenomas (a type of tumour from which cancer of the colon can develop).
In vitro research published in the International Journal of Biological Macromolecules found that certain compounds in white beans were able to block the growth and spread of cancer cells. This suggests that kidney beans may be a powerful food for fighting cancer.
Reduced your risk of obesity… several observational studies have linked the consumption of beans to a lower risk of being overweight or obese. A 2-month study of 30 obese adults on a weight loss diet found that eating beans and other legumes four times a week led to greater loss than a bean-free diet.
Another study published in the Journal of American College of Nutrition stated that increased consumption of beans may be linked to improved nutrition, lower body weight and reduced belly fat.
Kidney beans are high in dietary fibre and protein. Fibre moves through the body slowly thus prolonging feelings of satiety. Protein has been shown to reduce levels of ghrelin, a hormone that stimulates feelings of hunger.
Risks and side-effects from eating red kidney beans
Eating these beans is not all dietary heaven… problems include:
Flatulence… when eating beans some people experience unpleasant side effects such as flatulence, bloating and diarrhoea. These effects are due to alpha-galactosides, ie insoluble fibres. Alpha-galactosides can be removed, at least partially, by soaking and sprouting the beans.
Toxicity… raw kidney beans contain large amounts of phytohemagglutinin, a toxic protein. Though this protein is found in many beans, it is particularly high in these beans. Symptoms include diarrhoea and vomiting.
To get rid of this toxin, soak and cook the beans… soak them in water for at least 5 hours (or overnight, preferably) and boil them for at least ten minutes at 1000C (2120F). Properly prepared red kidney beans are safe to eat and very nutritious.
Antioxidants… are substances that reduce nutritional value by impairing the absorption of nutrients from your digestive tract. The main antinutrients in red kidney beans are:
- Phytic acid… aka phytate… impairs the absorption of minerals such as iron and zinc.
- Protease inhibitors… aka trypsin inhibitors… inhibit the function of various digestive enzymes, impairing the digestion of protein.
- Starch blockers… aka alpha-amylase inhibitors… impair the absorption of carbohydrates from your digestive tract.
All these antinutrients are completely or partially inactivated when beans are soaked and cooked properly. Fermenting and sprouting the beans may reduce some antinutrients, eg phytic acid, even further.
How to cook red kidney beans
Red kidney beans come in three basic forms… fresh, dried and canned.
You must not eat raw kidney beans unless you want to experience the heady joys associated with bouts of vomiting and diarrhoea.
Ideally, raw beans should be soaked overnight for at least eight hour before cooking. If they are soaked and sprouted before cooking, this will improve digestion and the absorption of nutrients.
Cook for a minimum of one hour to one-and-a-half hours using 3-parts water to 1-part beans.
Rather than cook your own beans, you can buy canned (tinned) beans which have already been cooked. The canned beans are just as nutritious as the raw beans except that they are often much higher in sodium. You should be able find low sodium varieties. If not, you can drain and rinse the beans… this will get rid of up to 41% of the sodium content.
But note that draining and rinsing canned beans could remove other micro-nutrients, such as vitamin C or the B vitamins. You can get around this by adding other healthy foods, such as carrots, onions, bell peppers and celery, to your meal to boost its nutritional value.
So, once you have the beans ready, what can you do with them?
Find out in the next article in this series… Recipes using red kidney beans