Green bean is the popular name for the protective pods and immature seeds of several types of cultivated beans. They are also known as snap beans and the most common varieties are the unripe fruits and pods of Phaseolus coccineus (runner bean), Lablab purpureus (hyancinth bean) or Vigna unguiculata subsp. Sesquipedalis (known as the yardlong bean).
Only the seeds of beans are normally consumed when they are fully ripe, the mature pods and are edible and have to be discarded. By contrast, green beans are eaten with their pods, which actually make up most of their mass since the fruits inside are small and immature. Unripe peas can be consumed in a similar way, when harvested young these are known as sugar snap peas or snow peas.
The origin of beans is lost in the mist of time, the English name of the plant comes from the old German languages. It is one of the oldest plants cultivated and eaten by humans and has been domesticated for thousands of years. In the wild, it is always a climbing plant. When cultivated, it can be a climbing variety (known as the pole beans) or not (bush beans). There are a huge variety of cultivated types and they come in all sizes and colors. The most common are the broad bean (Vicia faba), the runner bean (Phaseolus coccineus), the pinto bean, the wax bean, the kidney bean and the navy bean.
Green beans are very flexible plants, found on all continents and adapted to numerous climates. The cultivated pole climbing types can grow vines with a length of 2 to 3 m. Bush types will not exceed a height of 60 cm but can stay as low as 20 cm. Regardless of the variety, green beans have leaves with three leaflets with a width of 3-11 cm and a length of 6-15 cm. Leaves can be green or with a purple hint and are always alternate. The flowers have a size of around 1 cm and can be pink, white or sometimes purple. They develop into pods with a length between 8 and 20 cm but very thin, no wider than 1.5 cm. Their color also varies, from purple, yellow, green to black. Each pod houses 4 to 6 seeds, in the shape of a kidney, normally about 1-1.5 cm in diameter. There is a huge variety of colors, from white to black, some beans can have more than one.
The most useful compounds found in green beans are flavonoids, being one of the richest sources in nature for them. These are polyphenolic antioxidants are found in small amounts in many fruits and vegetables and can greatly decrease the risk of heart diseases. Besides, flavonoids have proven anti-inflammatory effects, especially in high doses like those encountered in beans. Researchers have made experiments with big amounts of flavonoids, revealing that blood clots stopped forming in arteries. High levels of flavonoids thus provide important anti-thrombotic benefits. Thrombotic activity is one of the most common causes for heart attacks, strokes and other heart diseases. As a result, constantly eating green beans to provide a big amount of flavonoids can potentially prevent these issues.
It was known for a long time that green beans have a high content of antioxidants but recent studies suggest the quantity is far greater than previously thought. Antioxidants are a key area of focus for modern medicine because they might be key in the treatment of many diseases. The human metabolism produces some compounds named free radicals, which are normally neutralized by our internal defence mechanisms. When these fail, the free radicals can cause irreparable damage to tissues and cells, antioxidants are the only way to destroy them.
Free radicals are considered to be one of the main causes of cancer, so antioxidants could be a way to fight this lethal disease. According to some scientists, eating green beans can stop the growth of pre-cancerous polyps that can later develop into colon cancer. However, other studies have found no connection between beans consumption and a lower risk of cancer. The latest results seem to show a direct link between a green beans diet and reduced occurrence of colorectal cancer and cancerous adenoma. This promising breakthrough has led to new research on the topic.
Beans are a great food choice for the very useful flavonoids and carotenoids, until recently the high content of these compounds was ignored. Beta carotene and lutein are the two main carotenoids found in green beans, both with significant antioxidant properties. Beta carotene is particularly beneficial, being thought to have a positive effect on a number of diseases. Flavonoids include many antioxidants, from simple types such as quercetin and keampferol to more complex ones like catechins and epicatechins. Catechins are good for heart issues because they weaken the consequences of strokes.
Like many other legumes, green beans are a great source of fibers. Fibers are excellent for digestion because they add bulk to the stool and decrease the speed of movement through the bowels. This reduces the pressure on the intestines and allows the digestive system to extract more nutrients from our food. Again, this appears to reduce the risk of colon cancer but the connection between a high fiber consumption and this disease has not been conclusively proven yet.
Another very common disease of today's world is diabetes. Diabetes requires constant monitoring of the level of sugar in the blood because high quantities can have disastrous consequences. The combination of bioactive compounds inside green beans have the power to regulate glycemic levels in many diabetes patients. Lab research has validated this claim, showing obvious hypoglycemic effects after eating green beans. Even if many internet sources claim otherwise, natural food that reduces blood sugar is actually very rare, so the beans are a must have for people with diabetes.
A special type of antioxidants from the carotenoids family found in green beans have the ability to protect vision. Lutein and zeaxanthin stop macular degeneration, the main cause for damaged vision that comes with aging. The two compounds protect the eye macula from free radicals and shield the internal mechanism of the eye from damage. They are rare in nature, so eating green beans can provide high levels of carotenoids and limit vision degeneration to a minimum.
Of course, fibers are a major benefit of green beans as well. This legume has a massive amount of fibers, which provide many health bonuses. Their main role is in digestion, a plentiful daily dose of fibers can cure or alleviate a wide range of related issues. Some of the digestive problems are mere irritants but others can be lethal. Some examples of digestive problems that can be directly influenced by the quantity of fibers in our diet are ulcers, acid reflux disease, hemorrhoids or chronic constipation. Green beans are some of the best vegetable sources of fibers. A single portion of beans, or just around 110 grams, provides 15% of the daily necessary amount of fibers.
Another key bioactive compound that can be rare in nature but is a part of green beans is folic acid, which is especially critical for women. Research has proven it plays many roles inside the human body but by far the most important one is to protect unborn children inside the womb. The development and health of the fetus is directly linked with the level of folic acid of the mother and high levels prevent issues related to the neural tube. This makes beans an awesome food choice during pregnancy, being both delicious and packed with folic acid and other useful vitamins.
The other nutrients in beans are known to fight osteoporosis and other bone degeneration diseases, thanks to a potent combo of calcium and vitamins. The action of calcium is boosted by the presence of silicon, as well as vitamins A and K. These bioactive elements usually work together and low levels will cause the weakening of the bones, which lose their weight, strength and structure. Silicon in particular is rarely found in important quantities in other foods, despite being one of the key building blocks of human bones. Green beans are thus a major resource in the fight against bone deterioration.
Green beans are generally safe and very few side effects have been identified. However, caution is always advised and the long history of consumption has revealed several potential risks.
A compound found in green beans that can sometimes cause problems is phytic acid. Eating too many beans will cause an overdose, which in turn leads to decreased nutrient intake. The problem is the acid reacts with some of the most important minerals, like zinc, and stops them from being processed. There is not a lot of phytic acid in beans but it can still become dangerous if you already lack minerals, whatever the reason, so they should be removed from the menu just in case. However, cooked beans have a much lower amount of phytic acid and are generally safe, avoid eating them raw.
Lectins are widespread compounds present in most food types. However, beans have a particularly high concentration. Of all bean varieties, the green ones have the lowest amount of these carb-binding proteins but their presence is still significant. The problem is lectin can combine with the intestinal flux and cause severe digestive issues, when their level becomes too high. Just like in the case of phytic acid, the lectin content can be decreased by cooking or simply soaking the legumes in water.
Another potentially dangerous compound in green beans is oxalic acid. Despite being a natural substance present in a number of vegetables, oxalic acid can turn into urinary stones in some people. If you've had such stones in the past, it would be better to exclude all vegetables from the Brassica and Fagaceae families from your diet. In general, people with kidney and urinary tract problems are advised to drink plenty of water in order to reduce the risk of stones forming by keeping the flow of urine at a healthy level.
Any food in the world can cause allergies to a small number of people, for reasons that have so far eluded modern science. If you are allergic to other legumes and feel any discomfort after eating green beans, it would be best to ask your doctor for advice.