Polar bear livers are edible, but eating them can be very dangerous due to their extremely high vitamin A content. Consuming more than 75g of polar bear liver can result in hypervitaminosis A which can lead to liver damage, bone pain, headaches, vomiting, bleeding, and even death. Polar bear livers contain the highest concentration of vitamin A found in any food.
Are Polar Bear Livers Toxic?
Yes, polar bear livers are toxic due to their extremely high concentration of vitamin A. Specifically, they contain massive amounts of retinol, which is the animal form of vitamin A.
Retinol is fat soluble, meaning it gets stored in the body’s fat deposits. Polar bears rely on their large fat reserves and vitamin A-rich diet of seals to survive the Arctic winters. This allows them to build up toxic levels of vitamin A in their livers.
For humans, consuming as little as 75-150g of polar bear liver can deliver a fatal dose of vitamin A. This level is many thousands of times higher than the recommended daily amount.
Symptoms of Vitamin A Toxicity
Consuming polar bear liver can rapidly lead to vitamin A toxicity called hypervitaminosis A. Symptoms may include:
– Severe headache
– Blurred vision
– Clumsiness due to decreased coordination
– Pain in bones and joints
– Itchy or cracked skin
– Abnormal softening of skull bones in infants
In high doses, vitamin A acts as a neurotoxin. It can alter cell membranes and gene transcription, leading to widespread physiological disturbances.
Without treatment, hypervitaminosis A leads to extensive liver damage. Ultimately it can cause bleeding disorders and coma as the liver loses its ability to manufacture clotting factors.
Fatal Doses of Polar Bear Liver
It only takes 75-150g of polar bear liver to deliver a potentially lethal dose of vitamin A to an adult human. This equates to just 2.6-5.3 ounces.
To put this in perspective:
– An average polar bear liver weighs 600-1,000g
– Recommended daily vitamin A intake is just 700-900mcg
So a whole polar bear liver contains around 1-1.5 million units (mcg) of vitamin A. This is over 1,000 times the recommended safe daily dose.
Even a small 150g piece would provide 300,000mcg of vitamin A, quickly leading to toxicity.
World Records for Eating Polar Bear Liver
Despite the dangers, there are some crazy records for consuming this toxic delicacy:
– In 1956, Canadian Eskimo hunters in Tuktoyaktuk consumed polar bear liver and fell ill, but survived the ordeal.
– In 1960, Australian Antarctic explorer Lincoln Ellsworth ate a full pound (450g) of polar bear liver, narrowly surviving vitamin A poisoning.
– But Norwegian explorer Roald Amundsen holds the record, having consumed 500g of polar bear liver in 1897 without apparent ill effects.
While a very small number of people have survived eating an entire liver, most would be killed by ingesting such a large amount.
Vitamin A Content of Polar Bear Liver
Here is the vitamin A content found in just 100g of raw polar bear liver:
|Vitamin A (IU)
|Vitamin A (mcg RAE)
|750,000 mcg RAE
To put this into context:
– 100g provides 150 times the recommended daily vitamin A intake.
– 100g could deliver a lethal dose for an adult human.
Safe consumption would be limited to just a few grams, rather than a whole liver.
How Do Polar Bears Tolerate Such High Vitamin A?
Polar bears have evolved to tolerate levels of vitamin A that would rapidly poison humans and other animals. Here’s how they manage to survive:
– Liver enzymes – polar bears have specialized cytochrome P450 enzymes that help them break down and excrete excess vitamin A.
– Fat reserves – polar bears store large amounts of vitamin A in their fat reserves and liver, releasing it slowly over time.
– Adapted receptors – the vitamin A receptor (RAR) in polar bear livers has adapted to bind less tightly to retinol, reducing its toxicity.
– Dietary habits – polar bears balance their vitamin A intake by alternating between seal meat and blubber in different seasons.
So while a whole liver would overload a human’s system, polar bears have adapted to handle their own naturally high-vitamin A diet.
Can You Make Polar Bear Liver Edible?
There are some methods that may make polar bear liver safe to eat in moderation:
– Cook it – Heat denatures the vitamin A, reducing toxicity. However, this can decrease nutrients.
– Soak it – Soaking raw liver in water leaches out some of the excess vitamin A.
– Freeze it – Freezing and thawing repeatedly may allow large vitamin A crystals to precipitate out.
– Ferment it – Bacteria used in fermentation like yogurt may help digest and reduce the vitamin A content.
However, these methods can’t remove enough vitamin A to make a whole liver safe to eat. At most, they may allow consumption of a small 30-50g portion.
Risks of Eating Polar Bear Liver
Despite potential techniques to reduce toxicity, eating polar bear liver still poses serious health risks:
– Liver damage – High vitamin A causes extensive liver injury that can be fatal. Recovery may require a liver transplant.
– Bone loss – Hypervitaminosis A accelerates bone resorption, leading to fractures and osteoporosis.
– Birth defects – High vitamin A causes severe developmental disorders in unborn children if eaten during pregnancy.
– Nerve damage – As a neurotoxin, vitamin A can irreparably damage nerves controlling arms, legs, breathing, and heart function.
– Kidney stones – Excessive vitamin A increases the risk of painful calcium oxalate stones in the kidneys.
Given the myriad of risks, polar bear liver should never be consumed except in tiny amounts. Hypervitaminosis A is extremely dangerous.
Alternatives to Polar Bear Liver
Instead of risking your health over polar bear liver, there are much safer ways to obtain vitamin A:
– Cod liver oil – Offers modest levels of vitamin A without toxicity risks.
– Liver from other animals – Has far less vitamin A than polar bears. Beef liver has 15,000IU per 100g.
– Carrots – Just one medium carrot provides over 200% your daily vitamin A needs.
– Sweet potatoes – An excellent source, with a single medium sweet potato providing over 700% vitamin A.
– Spinach – Leafy greens like spinach are packed with beta carotene, which your body converts to vitamin A.
– Cheese – Provides retinol, the active pre-formed vitamin A your body can use directly.
– Fortified milk – Many brands have vitamin A added, providing 30-40% of your needs per cup.
A balanced diet with vegetables, liver in moderation, and fortified foods can easily meet vitamin A requirements safely.
While polar bear liver is the most concentrated source of vitamin A in the world, it is simply too toxic for humans to eat in more than tiny amounts. Consuming a whole liver would be extremely dangerous and potentially fatal due to hypervitaminosis A. A few early Arctic explorers narrowly survived eating large amounts, likely aided by freezing or fermentation. However, the myriad health risks including liver failure and birth defects make polar bear liver unsuitable for consumption except in tiny thoroughly cooked quantities. Instead, vitamin A can be easily obtained from safer dietary sources like cod liver oil, carrots, sweet potatoes, and fortified dairy.