Kidney beans are rich in protein
- One cup of boiled kidney beans (177 g) contains approximately 15 grams of protein, accounting for 27% of the total caloric content.
- Although the nutritional quality of bean proteins is lower than animal proteins, beans are an affordable alternative for many people in developing countries.
- In fact, beans are one the richest plant-based sources of protein, sometimes referred to as “poor man’s meat”.
- The most widely studied protein in kidney beans is phaseolin, which may cause allergic reactions in susceptible individuals.
Kidney beans also contain proteins, such as lectins and protease inhibitors.
Other Plant Compounds
Kidney beans contain all sorts of bioactive plant compounds that may have various effects on health, both good and bad.
- Isoflavones: A class of antioxidants found in high amounts in soybeans. They have all sorts of health effects and are categorized as phytoestrogens due to their similarity to the female sex hormone, estrogen.
- Anthocyanins: A family of colorful antioxidants found in the skin of kidney beans. The color of red kidney beans is mainly due to an anthocyanin known as pelargonidin.
- Phytohaemagglutinin: A toxic lectin (protein) found in high amounts in raw kidney beans, especially red kidney beans. It can be eliminated with cooking.
- Phytic acid: Found in all edible seeds, phytic acid (phytate) impairs the absorption of various minerals, such as iron and zinc. It can be reduced by soaking, sprouting and fermenting the beans.
- Starch blockers: A class of lectins, also known as alpha-amylase inhibitors. They impair or delay the absorption of carbs from the digestive tract, but are inactivated with cooking.
- Bottom Line: Kidney beans contain a variety of bioactive plant compounds, both good and bad. Phytohaemagglutinin is a toxic lectin only found in raw or improperly cooked kidney beans.
- Overweight and obesity are major health problems, associated with increased risk for various chronic diseases.
- Several observational studies have linked bean consumption with lower risk of overweight and obesity.
- One trial in 30 obese men and women on a weight loss diet, found that eating beans (and other legumes) 4 times per week for 2 months led to greater weight loss than a diet that excluded beans.
- A recent meta-analysis of 11 randomized controlled trials also found some evidence supporting this, but was not able to draw a firm conclusion due to the poor quality of the included trials.
- Various mechanisms have been discussed as an explanation for the beneficial effects of beans on weight loss. These include various fibers, proteins, and antinutrients.
- Among the most widely studied antinutrients in raw kidney beans are the so-called starch blockers, a class of proteins that impair or delay the digestion and absorption of carbs (starch) from the digestive tract.
- Starch blockers, extracted from white kidney beans, have shown some potential as a weight loss supplement.
However, boiling at 212°F (100°C) for 10 minutes completely inactivates starch blockers, eliminating their effect in fully cooked beans .
Even so, cooked kidney beans contain a number of weight loss friendly components, making them an excellent addition to an effective weight loss diet.