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The term "legume" refers both to a plant whose fruit is enclosed in a pod, and to the Leguminosae family to whom these plants belong. Legumes are a dry fruit which develops from a simple carpel and is contained in a seed pod that splits along both sides when ripe. When the seeds of a legume are dried they are known as pulses.
The Leguminosoae family is one of the three largest families of flowering plants and consists of appoximatley 690 genera and about 18,000 species. This family is also known as the pulse, legume, pea, or bean family.
- There are three major groups within the Leguminosae family which are categorized based on the difference in the appearance of their flowers:
- Mimosoids: Consist almost entirely of tropical flowers, have reduced petals and usually have conspicuous, long stamens that give color to the flower clusters. The mimosoids includes species of industrial, forage, browsing, and fodder plants such as Acacia spp., the Sensitive Plant and the Silk Tree (Mimosa) which is a widely planted ornamental in the southern United States. The Australian black-wood (Acacia melanoxylon) tree provides useful timber and gum arabic from the tree of the same name (Acacia senegal) and is used in an variety of industrial processes.
- Caesalpinioids: Are characterized by well-developed petals and includes ornamentals such as the redbud and honey locust in temperate regions and the orchid trees of the tropics. The useful products derived from this subfamily include edible fruits (Tamarindus indica), senna medicine (Senna spp.), hematoxylon red dye from the logwood tree (Haematoxylon campechianum), resins used in paints, varnishes, inks, plastics, adhesives, and fireworks derived from the copal (Copaifera spp.) tree.
- Papilionoids: are the largest group in this family. Its members bear a flower that resembles the sweet pea, with a big petal at the top, a wing on either side, and a “keel” of two fused petals that enclose the stamens at the bottom. Many important agricultural plants are members of the Papilionoid group, including: peanuts, garden beans, soybeans, garden peas, lentils, chickpeas, cowpeas, clovers, and alfalfa.
Legumes can also be sub-categorized as either temperate or tropical based on their origin.
- Primary temperate legumes originate in humid, subhumid, subtropical, semiarid and temperate areas in areas around the world as far reaching as Southeast Asia and Guatemala. The primary temperate legumes used as human food sources include:
- Garden pea (Pisum sativum)
- Field pea (Pisum arvense)
- Winged pea (Tetragonolobus purpureus)
- Green bean (Phaseolus vulgaris)
- Runner bean (Phaseolus coccineus)
- Butter bean (Phaseolus lunatus)
- Lima bean (Phaseolus limensis)
- Soybean (Glycine max)
- Lentil (Lens culinaris)
- Broad bean (Vicia faba).
- Common tropical legumes are grown in areas that are humid, subtropical and tropical and originate primarily in Southwest Asia, Ethiopia, West Africa, China, Japan, India and South America. The tropical legumes commonly consumed by humans include:
- Winged bean (Psophocarpus tetragonolobus)
- Jicama (Pachyrhizus erosus and Pachyrhizus tuberosus)
- Chickpea (Cicer arietinum)
- Black-eyed pea (Vigna unguiculata unguiculata)
- Peanut (Arachis hypogaea).
- Legumes contain the plant compound phytosterol which works to inhibit the absorption of cholesterol, enhance immune function and exhibit anti-cancer effects.
- Legumes contain many vital nutrients such as calcium, and magnesium and provide a good source of thiamine, folic acid, vitamin E, iron, copper and dietary fiber.
- Legumes work to slow down carbohydrate absorption which helps to stabilize blood glucose levels.
- Legumes contain numerous essential amino acids and provide 2-4 times the amount of protein found in grains.
The cotyledon of the legume (which is comparable to the endosperm in grains) determines the nutrition content of the seeds and provides the nutrition necessary for the sprout to grow and develop. The root nodules of legumes are inhabited by Rhizobium bacteria which helps to preserve the nitrogen balance in soil.
- Adzuki Bean: These beans have been cultivated in Japan for hundreds of years are an important part of a macrobiotic diet.
- Alfalfa: Despite common perceptions alfalfa is actually a member of the pea family and therefore considered a legume.
- Carob: Carob is the fruit pod of the carob tree and is also known as the locust bean, locust pod or St. John’s bread.
- It is typically dried or roasted and often used in food preparation as an alternative to chocolate as it is mildly sweet.
- The seeds (locust beans) are used as animal feed, and are the source of locust bean gum which is a widely used food thickening agent.
- Chickpea (Garbanzo bean): The seeds of this bean are high in protein and often used in Indian and Middle Eastern cuisine and in vegetarian diets.
- Fava Bean: Fava beans are one of the oldest plants under cultivation, and despite their name are actually a member of the pea family.
- These beans are also known as broad beans, pigeon beans, horse beans, and windsor beans.
- Fava beans are rich in L-dopa, which is used to help control hypertension and in the treatment of Parkinson's disease.
- Fava beans are rich in tyramine and consequently should be avoided by anyone taking monoamine oxidase inhibitors.
- Raw broad beans contain the alkaloids vicine, isouramil and covicine, which have the potential to induce hemolytic anemia in patients with the hereditary condition glucose-6-phosphate dehydrogenase deficiency. This condition is potentially fatal and known as “favism”.
- Lentil: Lentils are one of the oldest cultivated plants in the world.
- Lentils are a good source of dietary fiber, folate, vitamin B1, and iron.
- They are a rich source of essential amino acids including lysine and isoleucine and have the third-highest level of protein by weight of any other nut or legume (30%).
- Lentils have been shown to prevent a spike in blood glucose levels after consumption of a meal and as such are beneficial in the dietary management of blood-sugar disorders.
- Lima Bean (Butter bean): Like many other legumes, Lima beans are a good source of dietary fiber, and a low-fat source of high quality protein.
- Peas: Fresh green peas are high in fiber, protein, vitamins, minerals, and lutein and are a good source of vitamin C, carotenes, calcium and phosphorus].
- Soybeans: Soybeans are the most widely grown and utilized legume and are considered to be one of the world’s most important foods.
- Soybeans are rich in vitamins A, E and B, calcium, folic acid, phosphorus, magnesium and potassium.
- Soy is one of the few plant source of alpha-linolenic acid, is chosterol free, low in saturated fat and provides a complete and rich source of protein.
- Soy products are packed with isoflavones including genistein and daidzein, which are powerful phytoestrogens.
- Depending on the type of estrogen receptor on the cells, isoflavones may reduce or activate the activity of estrogen, or compete with estrogen for the same receptor sites and thereby decrease the health risks of excess estrogen.
- Genisten appears to block tumor-cell growth, and studies indicate that consuming soy may reduce the risk of developing breast and prostate cancer, and have the ability to stabilize existing prostate cancers by decreasing PSA levels.
- The fiber contained in soybeans has been shown to provide numerous actions including: increasing fecal bulk and water content, decreasing intestinal transit time, reducing blood cholesterol and triglyceride levels, increasing insulin sensitivity and improving glucose tolerance.
- String Beans (Green beans, Snap beans): String beans are a good source of lutein, beta-carotene, violaxanthin, and neoxanthin.
- They contain very few calories per serving and provide excellent nutrition and dietary fiber therefore making them a beneficial food for weight-management.
Legumes and Flatulence
- Legumes contain oligosaccharides which are comprised of 3-5 sugar molecules linked together in a way that is hard for the body to absorb or digest.
- Once consumed these molecules pass into the intestines where they are broken down by bacteria who release a gas as they digest the oligosaccharides.
- The risk of gas production and subsequent flatulence can be reduced by properly cooking or sprouting legumes. 
- Soy can be difficult to digest which can result in a number of gastrointestinal problems.
- Soy has the potential to promote hormone-sensitive cancers in some individuals.
- Soy has been shown to demonstrate toxicity in estrogen-sensitive tissues, such as the endometrium while also effecting testosterone levels.
- In one study, treatment of 150mg/day (high dose) of soy isoflavones for five years also resulted in the development of endometrial hyperplasia in 3.9% of women.
- Moderate to high levels of soy consumption have been shown to lower testosterone levels and sex drive in men.
- Some soy products (specifically soy isolate) have been shown to inhibit levothyroxine and iron absorption.
- Soy has been shown to demonstrate toxicity in estrogen sensitive tissues and the thyroid.
Storing and Cooking Legumes
Following are some rules of thumb regarding storing and cooking legumes: 
- It is best to store dried legumes in dry airtight container in a cool dark spot. If stored properly dried beans and peas can last up to a year or more.
- Most dried legumes must be soaked before cooking as this reduces their cooking time, preserves their vitamins and minerals and reduces gas-related problems.
The recommended intake varies based on age and health status. To determine what your specific requirements are talk to your naturopathic doctor or other trained medical professional.
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