Lupines, part of the Lupinus genus, are popular flowering plants grown as ornamentals and as an important agricultural crop. They are valued for their high protein content in the seeds, making them a viable food source and livestock feed. However, many varieties of lupine are naturally poisonous, and the level of toxicity depends significantly on the specific species and how it has been processed. Lupine toxicity is a serious concern for both home gardeners with pets and the agricultural industry, requiring a clear understanding of the chemical compounds involved. Careful identification and preparation are necessary before any part of the plant can be considered safe for consumption.
The Chemical Basis of Toxicity
The natural toxicity in lupines stems from a group of compounds called quinolizidine alkaloids (QAs), which the plant produces as a defense mechanism against grazing animals and insects. These nitrogen-containing molecules are present in all species of lupine, though the concentration varies widely. The primary alkaloids involved include lupanine and sparteine, which are known to affect the nervous system.
These toxic compounds are concentrated most heavily in the seeds and seed pods, but they are also found in the leaves and stems of the plant. The high bitterness of these alkaloids often serves as a natural deterrent, preventing consumption. However, the sheer concentration of QAs in certain wild varieties means that even a small amount can cause adverse reactions.
The level of toxicity is directly proportional to the total concentration of these quinolizidine alkaloids within the plant tissue. Sparteine is considered highly toxic to humans, though its presence is often low in commercially grown lupines. Because these alkaloids are synthesized in the leaves and stems before being transported to the seeds, the entire plant should be treated with caution.
Distinguishing Between Toxic and Edible Varieties
The difference between a poisonous lupine and one that can be safely consumed lies in its genetics and cultivation history, resulting in a clear distinction between “bitter” and “sweet” varieties. Wild and ornamental lupines are typically the “bitter” types, containing high levels of quinolizidine alkaloids. This high concentration makes them highly toxic and unsuitable for direct consumption by humans or livestock.
“Sweet” lupines have been selectively bred since the early 20th century to contain significantly lower concentrations of these alkaloids. Species like Lupinus albus (white lupin) and Lupinus angustifolius (narrow-leafed lupin) have been developed for agricultural use, allowing their seeds to be used for food and feed after minimal processing. However, even these sweet varieties still require a process called “debittering,” which involves soaking and rinsing, to remove the remaining trace alkaloids and make them palatable.
The high alkaloid content in bitter lupines presents a specific danger to grazing livestock, particularly sheep, which are highly susceptible to acute poisoning when consuming the seeds and pods. A serious condition known as “Lupinosis” is a liver toxicosis caused by a fungus that grows on lupine stubble, which is a separate but related risk in livestock management. Furthermore, cattle that graze on certain toxic species during specific stages of early pregnancy can give birth to calves with skeletal deformities, a condition known as “Crooked Calf Disease.”
Symptoms of Ingestion and Necessary Action
Ingestion of toxic lupine varieties, or insufficiently processed bitter lupine seeds, can lead to a condition characterized by anticholinergic effects, impacting the nervous, circulatory, and digestive systems. The onset of symptoms in humans is typically rapid, often occurring within an hour of consumption. Mild to moderate symptoms include nausea, vomiting, dizziness, and a pronounced dry mouth (xerostomia).
The alkaloids can also affect the nervous system, leading to blurred vision, dilated pupils (mydriasis), confusion, and loss of motor coordination. While human fatalities are rare, severe poisoning can escalate to life-threatening conditions, including respiratory depression, paralysis, or cardiac arrest. Children and individuals with lower body weight are more susceptible to severe reactions from smaller quantities.
In animals, signs of lupine poisoning include lethargy, nervousness, loss of appetite, and lack of muscular control leading to a staggered gait. Livestock, especially sheep, can exhibit frothing at the mouth, convulsions, and difficulty breathing. If there is any suspicion that a human, pet, or livestock animal has ingested any part of a bitter or wild lupine, immediate action is necessary.
The first step is to immediately contact a poison control center or emergency medical services. Attempt to identify the specific type of lupine ingested if possible, as this information is helpful for medical professionals determining the severity of the exposure. Medical intervention is often required to manage symptoms, and in cases of severe poisoning, detoxification measures may be necessary.