For decades, scientists and the public alike have been intrigued by one particularly resilient group of animals: sharks. Among the many myths and facts surrounding these ancient predators, one claim has stood out and persisted—sharks rarely, if ever, get cancer. While this is not entirely accurate, it is true that sharks show a much lower incidence of cancer compared to many other species.
This unusual resistance has fueled scientific studies, pharmaceutical interest, and even a wave of health supplements. But what is the real story behind this phenomenon? And what can we learn from it?
The Origin of the Shark Cancer Myth
The idea that sharks are immune to cancer gained popularity in the 1990s, primarily due to the bestselling book Sharks Don’t Get Cancer by Dr. William Lane. The book popularized the notion that sharks, due to their unique biology, were free from this devastating disease and could offer a key to curing cancer in humans. While the title was catchy, the claim was exaggerated. In truth, sharks can develop cancer—but much more rarely than other animals.
Still, the underlying idea wasn’t entirely baseless. Scientists and marine biologists had long noticed the remarkably low rate of tumors in shark populations, especially considering their long lifespans and exposure to environmental toxins. This led to a growing interest in understanding what sets them apart at a molecular and physiological level.
What Science Actually Says About Shark Cancer Resistance
Sharks are not immune to cancer, but they do possess several unique biological features that contribute to their lower susceptibility:
- Highly efficient immune systems: Sharks have one of the most sophisticated immune systems in the animal kingdom. They rely on a strong innate immunity, which includes a highly efficient system of white blood cells that can detect and destroy abnormal cells quickly.
- Cartilaginous skeletons: Unlike mammals and other vertebrates, sharks have skeletons made entirely of cartilage. Since cartilage has no blood vessels, it is thought to limit the spread of cancerous cells. Tumors require a blood supply to grow and spread (a process called angiogenesis), and the low vascularity of cartilage may act as a natural barrier.
- Unique wound healing: Sharks have an exceptional ability to heal wounds without infection or scarring. Some researchers speculate that this regenerative capacity may be linked to mechanisms that also suppress cancer development.
- Strong DNA repair mechanisms: Some studies suggest that sharks have highly effective DNA repair processes. This means their cells are better equipped to correct mutations before they can lead to tumor formation.
Genetic Research and Recent Discoveries
In recent years, advances in genetic sequencing have provided scientists with new tools to study shark genomes. One landmark study conducted by the Save Our Seas Foundation Shark Research Center and published in Proceedings of the National Academy of Sciences examined the complete genome of the great white shark (Carcharodon carcharias). The findings were remarkable.
Researchers found that the shark genome contains genes related to DNA repair, genome stability, and cellular resistance to stress that are significantly enriched compared to other vertebrates. These genes are involved in:
- Maintaining chromosome integrity
- Suppressing tumor growth
- Reducing oxidative damage
These adaptations are not only important for cancer resistance but also for ensuring long lifespans and survival in harsh marine environments. The implications for human medicine are enormous. If we can understand and replicate some of these genetic processes, we might improve cancer prevention and treatment in humans.
The Role of Shark Cartilage in Cancer Therapy
Much of the public’s interest in shark cancer resistance was driven by the rise of shark cartilage supplements. These were marketed in the 1990s as natural cancer cures or preventatives, often without scientific backing. The rationale was that since shark cartilage might suppress angiogenesis (the growth of blood vessels that tumors need), ingesting it could prevent tumors from forming or spreading.
However, multiple scientific reviews and clinical trials have found little to no evidence that shark cartilage supplements have any real effect on cancer in humans. The U.S. Food and Drug Administration (FDA) and cancer research organizations like the American Cancer Society have stated that shark cartilage is not a proven treatment and should not be relied upon in place of traditional therapies.
Moreover, the harvesting of sharks for cartilage supplements has raised ethical and environmental concerns. Many shark species are now endangered due to overfishing, and the exploitation of sharks for unproven supplements has contributed to population declines.
What Sharks Can Really Teach Us
Rather than relying on shark cartilage pills, the real promise lies in studying the molecular biology of sharks in controlled scientific environments. Sharks have existed for over 400 million years and have developed an extraordinary set of adaptations for survival. Their low cancer rates, combined with their genomic stability and efficient immune response, make them ideal subjects for biomedical research.
Future studies may help uncover how we can:
- Improve DNA repair pathways in human cells
- Develop new cancer-resistant genes or gene therapies
- Create drugs that mimic shark biology without harming shark populations
Challenges and Limitations
While sharks provide fascinating insights, there are limits to how much we can translate from their biology to human medicine. Humans and sharks diverged evolutionarily hundreds of millions of years ago. What works in one species may not function similarly in another. Additionally, ethical concerns about marine life conservation must always be weighed against research interests.
The belief that sharks are completely immune to cancer is a myth—but it is a myth rooted in biological reality. Sharks do get cancer, but far less frequently than many other species, including humans. This resistance is likely due to a combination of factors: their immune efficiency, unique skeletal structure, genetic resilience, and powerful DNA repair mechanisms.
Rather than exploiting sharks for commercial supplements, the scientific community has shifted its focus toward studying their genome and biology for clues that may one day enhance cancer treatment in humans. While there’s no miracle cure to be found in a shark’s cartilage, there may be a biological blueprint worth decoding—one that could eventually help us fight cancer more effectively and ethically.
