Is It True That Sharks Do Not Get Cancer?
Sharks definitely do get cancer. Scientists have known for more than 150 years that sharks get cancer and yet the belief persists that they don’t suffer from the disease. However, they get it far less often than humans do. The idea that sharks are immune to cancer was popularized by the title of William Lane’s 1992 book Sharks Don’t Get Cancer.
However, inside his book Lane admitted that sharks do get cancer. Although it is theorized that shark cartilage might inhibit the growth of tumor blood vessels, studies have shown that ingesting shark cartilage does not confer any anti-cancer benefits. That misconception is promoted in part by those who sell shark cartilage, who claim that the substance will help cure cancer, said David Shiffman, a shark researcher and doctoral student at the University of Miami.
But no studies have shown that shark cartilage is an effective treatment, and the demand for the material has helped decimate shark populations, researchers say: Humans kill about 100 million sharks per year, according to a March 2013 study (although many factors contribute to the killing of sharks, including demand for shark-fin soup).
The belief that shark cartilage can treat cancer diverts patients from effective treatments, according to a 2004 review in the journal Cancer Research. The demand for cartilage also fuels widespread fishing for sharks. One in six known species of sharks, rays and skates are considered threatened with extinction by the International Union for Conservation of Nature, an environmental group, Shiffman said.
The reports of cancerous tumors in marine animals, especially mammals, have steadily increased over the past 20 years, raising concerns that industrial pollutants or human activities may trigger the cancers, according to the study. Beluga whales have been recorded to suffer from cancer and in areas near aluminum smelting plants, cancer is the second leading killer of the whales, the study noted.