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Alfalfa: a hazardous food?
Can any plant be more politically correct than alfalfa? It’s almost obligatory in greenie circles to eat alfalfa sprouts in as many ways as possible. Alfalfa sprouts, however, provide a dramatic demonstration that the real hazards from food come from natural sources, not man-made ones.
Canavanine: a toxic arginine analogue
Small-seeded legumes like alfalfa and broom have developed a protective chemical called canavanine. Alfalfa seeds are about 0.5% canavanine, compared with 13% in seeds of the tropical legume Dioclea megacarpa. Just 0.02% canavanine can harm insect larvae. Any animal that ingests canavanine makes incorrect proteins that malfunction as enzymes. The damage is non-specific and widespread, affecting RNA and DNA metabolism, as well as a key enzyme for destroying alcohol. Because it messes up so many aspects of metabolism, canavanine is a highly toxic chemical to animals. Pigs refuse to eat feed containing too much canavanine.Although we humans are not immune to canavanine, we don't seem to taste it.
Canavanine causes lupus-like disease
Canavanine poisoning is particularly dangerous for people with systemic lupus erythematosus (SLE), an autoimmune disease in which the person’s defence systems inadvertently attack the body itself. Mild cases produce fatigue and aching joints, similar to arthritis, but severe cases can be lethal. SLE comes and goes, but canavanine may be able to produce another attack. When rhesus monkeys were put on a diet containing “dried alfalfa (‘lucerne’ to Europeans)”, some of them exhibited an SLE-like disease, which slowly receded when they went back to ordinary monkey chow. There are medical reports of people who took large quantities of alfalfa pills and who thereby reactivated systemic lupus erythematosus. Canavanine poisoning is a real possibility!
Should you throw away the alfalfa sprouts in your refrigerator? Even though some of the canavanine from the alfalfa seeds has been converted into other amino acids, the sprouts contain detectable levels of canavanine. However, these levels are low, and even a lupus sufferer can probably consume a single portion of an alfalfa-sprout salad. It takes quite high doses to produce recognisable symptoms of canavanine poisoning. Nevertheless, if you unexpectedly develop arthritic symptoms, it might be time to re-evaluate your consumption of alfalfa sprouts.