They were participating in the rite of passage of many Arctic explorers. To supplement the tinned meat they carried with them, they had killed an animal, cooked it into a stew, and eaten it. This animal was a polar bear – an impressive catch given that they were known for surviving multiple gunshots at point-blank range. The explorers, surrounded by a frozen wasteland and knowing that they wouldn’t see their homes for many months, likely took comfort in a meal that would help them live another day.
Then their skin started to peel away from their bodies.
It didn’t happen immediately – first came the drowsiness, headaches, and vomiting. But in time, the skin around their mouths began to peel. For some of the more fortunate explorers, the peeling was limited to their faces. Others lost skin over their entire bodies.
The culprit was the polar bear’s liver, which had been cooked into the stew. Peter Freuchen, a member of the Danmark Expedition (1906-1908), wrote: “We had never heard the old superstition that bear’s liver is poisonous but in our case the superstition certainly proved true”. In other cases, explorers could have avoided their poisonings by listening to the advice of the local indigenous people. Elisha Kent Kane (Grinell Expedition, 1853) wrote:
“I satisfied myself that it was a vulgar prejudice to regard the liver of the bear as poisonous…But I find to my cost that it may sometimes be more savoury than safe. The cub’s liver was my supper last night, and today I have the symptoms of poison in full measure – vertigo, diarrhoea, and their concomitants [sic]”.
What these explorers couldn’t have known was the bear liver’s toxicity was due to extremely high levels of vitamin A, leading to a condition known as acute hypervitaminosis A – a vitamin A overdose. Vitamin A is important for vision, immunity, and reproduction, and, because of its roles in cell growth, is critical for the development and maintenance of organs – including skin. But it is possible to have too much of a good thing. When vitamins dissolve in water, as vitamins B and C do, any excess vitamins will leave your system when you go to the bathroom. But because vitamin A instead dissolves in fat, it gets stored in your body, primarily in your liver. Too much vitamin A disrupts the same processes that it usually maintains, leading to blurry vision, headaches, vomiting, birth defects…and peeling skin.
As with the arctic explorers, your vitamin A comes from your diet. When you eat plants, you get “provitamin A caretenoids”, the building blocks that our body will use to make vitamin A. When you eat animal products, you get “preformed vitamin A”. You can eat as many vegetables as you want without harm; once you’ve reached your ideal vitamin A levels, your body will stop transforming the provitamin A. But preformed vitamin A builds up in the livers of all animals. Polar bears have a high tolerance for vitamin A, which is good because seals (and all of the vitamin A-rich blubber that comes with them) make up a major part of their diet. Humans, however, have a much lower tolerance for vitamin A; the highest tolerable amount of vitamin A per day is 3,000 mcg. A single gram of polar bear liver can contain two times that amount.
Polar bears are not the only animals with toxic livers. The livers of seals, and even arctic sled dogs, have been known to cause hypervitaminosis A in humans. However, today the most likely cause of hypervitaminosis A is taking too many vitamin A supplements. Fortunately, hypervitaminosis A is both rare and simple to treat: stop taking vitamin A, and a doctor can treat your symptoms until you return to normal. And as a general rule of thumb: if you’re traveling, and the locals tell you to avoid a specific food because it’s toxic, just believe them.
Peer Editor: Grace Stroman