The Health Benefits of Sharks

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Sharks have thrived for 400 million years. They get less cancer and are less susceptible to certain viruses than we are. They're also called "majestic" more often than many of us. But we've failed to steal their proverbial flavor.

sharkdivemain.jpg11.5 foot Great White plunges under a diving cage off of Cape Town (MikeHutchings/Reuters)

There used to be a rumor that sharks don't get cancer. Then it turned out that they do, just apparently less frequently than humans. Still their relative immunity presented a viable avenue for further clinical and biochemical research. First, though, we thought, let's grind up their bones and eat them and see what happens.

It's a pretty primal instinct, to eat the thing whose virtues you seek. Michael Jordan got cut from his high school varsity basketball team as a sophomore, so the following summer he famously dined entirely on gazelles.* And then, jumanji, next thing you know they named sneakers after him. It's a wonder we're not trying to eat Jordan. 

Shark cartilage has since been used as adjunctive therapy in cancer, osteoarthritis, psoriasis, and macular degeneration. But the evidence for it is slim and the outcomes largely disappointing. Meanwhile the case against it includes a "dramatic decline in shark populations and a diversion of patients from effective cancer treatments."

The drug Neovastat, which is an aqueous shark cartilage extract, does enjoy orphan drug status from the FDA for the treatment of late-stage renal cell carcinoma, but overall shark cartilage is generally regarded as one of those good prospects that unfortunately hasn't panned out. It even appears to be detrimental beyond the environmental and misallocated financial costs, in that it's been reported to contain some unnerving neurotoxins.

SHARK300200.jpgWhale shark in Indonesia (DwiOblo/Reuters)

There is some promise in shark liver extract as a broad-spectrum antiviral medication (squalamine), as well as a therapy for macular degeneration, but studies are still ongoing.

Apart from eating or injecting sharks into us, there may be less invasive ways to benefit from their healthiness. How do I get shark healthy -- today?

***

Animal-assisted therapy has shown benefits for several conditions, such as schizophrenia, hypertension, and chronic pain. Walking around hospitals I've seen a lot of cartoonishly fluffy therapy-dogs that love to be petted and parade around the hospital making spectacle of their sweeping tales and looking into the eyes of patients with indiscriminate affection, affirming our inherent value as humans with petting hands. They theory is that they're calming, distracting, stimulating, healing, etc. There was even a miniature horse in a veterans' hospital once. It was the size of a German shepherd, and it was stoic and didn't have a diaper on. But I can't say the connection was there as much with the horse. His eyes, they were vacant.

Some people do dolphin-assisted therapy, where they swear by swimming with dolphins, which I can't imagine wouldn't raise your spirits and take your mind off of things for a while. Actually, though, that's fraught with objection, primarily from animal rights advocates, and has been called a "lose-lose situation for dolphins and people."

On the BBC/Smithsonian Channel show Shark Therapy, "world-champion free diver" Tanya Streeter swims all up in sharks' business as she "pushes herself to the limit in order to conquer her worst fears." That doesn't sound therapeutic at all, and while getting up in sharks' business as a manner of therapy is more humane than killing 38 million of them per year to inject them into our bodies and eat, it's not accessible to many.

SharkTherapy - SmithsonianChannel.jpgShark Therapy (Smithsonian Channel)

For the rest of us, we have Discovery Channel's Shark Week. The brief week each year where the simple presence of the healthful majesty of sharks cleanses the masses as we cower in the glow of our television screens playing thematic drinking games.

We have visceral, primal reactions to the sharks. It's not sexual, but it's at least partly sexual. It's not real fear, because we know we're not going to get eaten, but it's at least partly fear. 

The mechanism by which shark cartilage would theoretically prevent human tumors is its ability to inhibit angiogenesis. That is, by preventing new blood vessels from growing to supply tumors. Without blood vessels, tumors won't grow. Meanwhile, norepinephrine and epinephrine (adrenaline) -- which our adrenal glands release instinctively when we get scared -- are proangiogenic. That is, they promote new blood vessels and facilitate tumor growth.

So if you're the type who gets spooked by watching Shark Week in the dark in HD or has heart-racing nightmares all week about sharks coming up through your toilet, then even if you're gorging yourself on expensive, chalky shark cartilage pellet supplements every morning, sharks may actually be doing more to give you cancer than they are to fight it.

Ultimately, then, sharks are probably most beneficial to our health as models of physical prowess and grace. Many species need to keep moving in order to breathe -- the sort of fact you learn from watching Shark Week. And while you could emulate their behavior as a call to lead a less sedentary life, there's also the metaphysical invocation. In a way, do we not all need to keep moving lest we perish? "Like a rolling stone, like a rolling stone..."



*Untrue

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James Hamblin, MD, is a senior editor at The AtlanticHe is the host of If Our Bodies Could Talk.

 
 
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