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Why Whales Have Oil in the Liver

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While all vertebrates have fat-rich, calorie-dense livers -- the majority lack a distinct oil. By contrast, many fish and some marine mammals have some amount of oil in their livers. Though scientists do not fully understand the importance or purpose of these oils, they do know that many -- including those harvested from whales -- are rich in vitamin A and related compounds.

Typical Mammalian Livers

The liver of most mammals are remarkably similar and perform similar functions. The liver is the largest glandular organ in the body, and one of the most important. Among other things, the liver cleans the blood of damaged cells, ammonia and toxins; it stores excess sugar as glycogen; and it produces and stores bile, primarily used to digest fats. Livers have impressive powers of regeneration, and as long as 25 percent of the liver is healthy, it can replace the diseased, damaged or missing portion.

The Livers of Whales

Whales carry their livers in approximately the same place as humans do -- in the abdomen, beside the stomach. While large in absolute terms, most whale livers are also large relative to the size of the animal -- blue whale (Balaenoptera musculus) livers can weigh more than 2,500 pounds and represent about 10 percent of the weight of the entire animal. A shallow indentation usually divides whale livers into two lobes, but they occasionally possess another indentation, yielding a third lobe. Whales and dolphins lack gall bladders; instead, they store bile in the duct system of the liver.

Whale Liver Oil and Kitol

The oil in whale livers contains a substance called kitol, though scientists do not yet fully understand its purpose or function. Scientists do not even agree if the whales produce the oil or if it comes from their diet. Kitol appears likely to be an inactive form of vitamin A. As vitamin A is toxic in high doses, it's possible that whales produce kitol as a way to avoid toxicity problems. Unlike some fish, which use the oil to store energy for seasonal movements, whales store most of their energy as blubber. The liver oil of fish also contributes significantly to their buoyancy; however, as air-breathing mammals, whales carry large lungs full of air, which help them to float.

Benefits for Humans

Some people take various marine oils -- including that derived from whale livers -- for the purported health benefits. Food meal made from whale liver has shown to be a viable food source for farm animals, and is rich in B-complex vitamins. Traditionally, whale oil had many commercial uses, including as a lubricant and fuel. However, in these cases, the oil was a heterogeneous mixture, rendered from many parts of different whale carcasses, such as the large heads of sperm whales.