Toxicity in humans by ingestion of colocasia esculenta elephant ear
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Toxicity in Humans by Ingestion of Colocasia esculenta (Elephant Ear). Audrey Medina Barry Sandall Loucia Jose Biology 445 May 04, 2007. What is Colocasia esculenta ?. Herbaceous, flowering plant of the family Araceae. Commonly referred to as ‘Elephant Ear’

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Toxicity in humans by ingestion of colocasia esculenta elephant ear l.jpg

Toxicity in Humans by Ingestion of Colocasia esculenta (Elephant Ear)

Audrey Medina

Barry Sandall

Loucia Jose

Biology 445

May 04, 2007

What is colocasia esculenta l.jpg
What is Colocasia esculenta?

  • Herbaceous, flowering plant of the family Araceae.

  • Commonly referred to as ‘Elephant Ear’

    because of its large leaves

    resembling elephant ears.

  • Grown in tropical areas as a staple food resource (taro) by many indo-asian countries

Description l.jpg

  • Perinnial monocot

  • Large, arrowhead-shaped leaves can grow to be 3’ X 2’

  • Long stalk

  • Flowers are arranged in a spadix with green or yellow spathe

  • Tarocorms present in the root

    • similar in appearance to a yam or potato

Distribution l.jpg

  • Native to tropical Polynesia and southeastern Asia

  • Grows naturally in tropical and subtropical areas but will grown in temperate climates as well

  • Introduced to United States, considered an invasive species in some areas

Slide5 l.jpg

  • Grown primarily as a vegetable food for its

    edible corm

  • Taro corms are used most

    famously in the Hawaiian

    dish known as poi.

  • Also grown as a leaf vegetable for food.

  • Popular in the United States for its foliage and used mainly for aesthetic purposes.

Toxic parts of plant l.jpg
Toxic Parts of Plant

The entire plant is toxic!

Leaf, stem, and root.


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Signs and Symptoms

If Ingested Raw:

  • Intense burning and irritation of lips, mouth, tongue, and throat.

  • Vomiting

  • Diarrhea (Uncommon)

  • Base of tongue swells and can be fatal if swelling is large enough to block the air passage of the throat.

  • Death by asphyxiation!

Toxic agent l.jpg
Toxic Agent

  • Elephant ear contains calcium oxalate crystals which are needle-shaped and arranged in compact bundles.

  • When chewed the crystals are ejected from specialized explosive ejector cells.

  • Needles get lodged in the lining of the mouth, tongue, and throat leading to local inflammatory reactions.

Toxic principle l.jpg
Toxic Principle

Calcium oxalate crystals-Raphides

  • Oxalate is an unstable salt of oxalic acid

  • Oxalic acid is soluble in water, alcohol, and ether.

  • Composed of:

    2 carboxyl groups

  • Creates dangerous

    free-radicals in body.

Mechanism l.jpg

  • Needle fibers induce inflammatory response and edema in oral cavities and mucous membranes.

    • Can lead to aphyixiation

  • Calcium oxalate dissolves in the stomach to form oxalic acid.

    • more readily absorbed into the

      blood and circulation system.

    • Very dangerous if ingested in large amounts

Toxicity l.jpg

  • Oxalic acid can binds with calcium in the body resulting in hypocalcemia.

    • Can lead to muscle cramps, hypotension, bradycardia, and cardiac arrhythmia.

  • Binding of oxalic acid with calcium in the body can induce crystallization of calcium oxalate.

  • Calcium oxalate can build up in the body.

    • Major cause of kidney stones.

    • Can lead to liver and kidney failure and cause permanent damage.

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Treatment and Other Precautions

  • Calcium chloride and calcium gluconate should be administered for large ingestion of plant…why?

    • Calcium chloride and gluconate act by replenishing the calcium in the circulation, thus reducing the toxic effects.

    • Providing extra calcium reduces the toxic danger of the

      free oxalic radicals.

  • As a precaution, Elephant Ear

    should be eaten with milk or

    other foods rich in calcium.

Summary of toxicity l.jpg
Summary of Toxicity

  • Oxalate crystals on plant cause extreme inflammatory immune response which may lead to death.

  • Minor gastrointestinal distresses to serious heart conditions can be caused by low calcium levels due to oxalic acid ingested from Colocasia esculenta.

  • Kidney stones, major organ failure,

    and tissue damage can also result

    from deposits of calcium oxalate,

    formed by oxalic acid binding

    calcium in the body.

Conclusions l.jpg

  • Colocasia esculenta (Elephant Ear, taro) can cause many toxic effects in humans with potential for serious damge or death.

  • Colocasia esculenta should NEVER be eaten raw.

  • Proper cooking methods and precautions should be followed closely.

  • Calcium should be taken appropriately when ingesting.

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Conclusions cont…

  • Taro must be the most delicious dish in the world.

  • Because, really, why the hell is anyone eating this thing?

  • Yummy!

References l.jpg

Beaulieu, David. 2007. Elephant Ear Plants. About: Landscaping.


Kuhlken, R. 2002. Intensive Agricultural Landscapes of Oceania. Journal of Cultural Geography. 19: 161-195.

Plant Profile: Colocasia esculenta . USDA Natural Resources Conservation Services. 2007. <>

Tagwireyi, D. and Ball D.E. 2001. The management of Elephant’s Ear

poisoning. Human & Experimental Toxicology. 20: 189-192.

Wagner, W. L., D. R. Herbst, and S. H. Sohmer. 1999. Manual of the Flowering Plants of Hawai‘i. Revised edition. Vol. 2. University of Hawaii Press/Bishop Museum Press. p. 1357.