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Alfalfa (Medicago
sativa)
General Description
Alfalfa (also known as lucerne or purple medic) is a perennial legume of the pea
family, native to western Asia and the eastern Mediterranean region and
cultivated throughout much of Europe, North America, and South America. The
plant has an erect stem growing 40 to 90 centimeters tall, and grayish-green,
clover-like leaves. Alfalfa flowers throughout much of the summer, bearing
clusters of small, blue or purple flowers, which produce coiled pods containing
multiple seeds. Perhaps the most remarkable attribute of alfalfa is its
extremely deep root system, which may reach depths as great as 15 meters in
porous subsoil. After just five months of growth, the tap root may reach as deep
as two meters. Cultivated primarily for hay and silage, alfalfa has a remarkable
capacity for rapid regeneration of stems and leaves after cutting, allowing
several crops of hay in one growing season.
Health Applications
- General nutrition
- High cholesterol
- Diabetes
History and Traditional Use
Alfalfa is believed to have originated near Iran, but it has been naturalized
thoughout much of the world. As early as 490 B.C., Roman writers described
alfalfa's value as feed for horses and other animals,1 and it remains
an important component in the diets of dairy cattle, horses, beef cattle, sheep,
and goats. Alfalfa is the oldest cultivated forage crop in the US, introduced
into eastern North America by colonists in 1736.1 The leaves and
seeds of the plant have been used for a variety of medicinal purposes ranging
from diabetes, poor appetite, urinary and bowel problems, water retention, and
arthritic complaints.2,3 However, there is little scientific evidence
to support these traditional applications. Chemical Composition
A rich source of protein, fiber, and vitamin K, alfalfa also contains
carotenoids (especially lutein), saponins, isoflavonoids (including glycosides,
genistein, and diadzein), triterpenes, coumarins, glycosides, fatty acids, and
betaine.4
Diabetes/High Cholesterol
While the effects of alfalfa on animals have been studied extensively, very few
studies have examined the herb's effects on humans. Most studies on the
medicinal properties of alfalfa have centered on its purported
cholesterol-lowering and antidiabetic properties. Studies conducted on
diabetic-induced mice indicate that compounds in alfalfa may help stimulate
insulin secretion and lower blood sugar levels.5,6 Alfalfa saponins
were found to inhibit cholesterol absorption in rats,7 and
preliminary human studies indicate that alfalfa seeds may lower both total
cholesterol and LDL (the "bad" cholesterol) levels.8,9
However, no large-scale studies have been conducted to confirm these preliminary
findings.
Dosage/Toxicity
No therapeutic dosage of alfalfa has been established for humans. Consumption of
alfalfa leaves and seeds have not been associated with any toxicity. Alfalfa
sprouts have induced symptoms of systemic lupus erythematosus (SLE) in lab
experiments, apparently due to the action of L-canavanine, an amino acid found
in alfalfa seeds and sprouts. In vitro studies indicate that L-canavanine
influences the activity of immunoregulatory cells, which may account for
lupus-inducing activity.10 Consequently, many herbalists recommend
that people with SLE avoid alfalfa products. In recent years, consumption of
fresh alfalfa sprouts, a popular ingredient in salads and sandwiches, has been
associated with outbreaks of Salmonella and E. coli infections. Until effective
measures are found to prevent sprout-associated disease, people who wish to
reduce their risk for food-born illnesses (in particular, the elderly, children,
people with compromised immune systems, and others at risk for severe
complications of E. coli or salmonella infection) should not eat raw sprouts.11
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