Shark cartilage supplements are promoted
by some alternative medicine practitioners
due to their supposed anti-cancer properties.
Is there any truth to that? Let’s find out.
"The Truth About Shark Cartilage Pills"
An assessment of websites on complementary and alternative medicine
for cancer found that many endorse unproven therapies
and some that are outright dangerous,
potentially exploiting highly vulnerable patients
and enriching irresponsible snake oil peddlers,
or for that matter, shark cartilage peddlers,
accounting for millions of dollars of sales every year.
Why shark cartilage of all things?
Interest in shark cartilage as an anticancer agent arose
because many people believe that sharks did not get cancer.
Why would they think such a thing?
Because some shark cartilage supplement hawker wrote a book called,
"Sharks Don't Get Cancer."
But that's simply not true.
Sharks do get cancer.
Both benign and cancerous lesions have been reported in 21 species of sharks
more than 9 families.
For example, this oral tumor spilling out of the mouth of a great white.
Now some shark cartilage distributors insist instead that sharks just rarely get cancer,
but actual cancer rates in sharks have never been determined.
There's simply been no systematic tumor surveys of sharks
for them to make such a claim.
But look, even if sharks were less susceptible to cancer,
how can one logically jump from that to cancer patients benefiting
from eating powdered cartilage from a shark?
We know, for example, that there are certain proteins that allow
some bacteria to survive in like boiling hot springs.
Uh, does that mean if we eat those bacteria we can survive boiling water, too?
It doesn't make any sense.
The illogic behind the pursuit of shark cartilage therapies has implications
beyond the reduction of shark populations
and the misdirection of patients to ineffective cancer therapies.
The stuff may be harmful, and I'm not just talking about
the rare case of shark cartilage-induced liver inflammation.
Shark products can contain the neurotoxin BMAA, which I've talked about before.
It's been detected at elevated levels
in the brains of Alzheimer's disease and ALS patients,
and may play a role in the development of neurodegenerative disease.
So like the consumption of shark fin soup or
something may pose a significant health risk,
but what about shark cartilage supplements?
They tested sixteen commercial shark cartilage supplements, right off the shelves,
and found BMAA in fifteen out of sixteen.
But look, even if shark cartilage supplements carry pro-inflammatory properties,
which could pose a potential health risk for consumers, we're talking about cancer.
There are chemotherapy agents that are life-threateningly dangerous,
but sometimes the benefits can outweigh the risks when confronted with cancer.
So the question then becomes: are there any benefits to shark cartilage?
I mean, it's not a completely whacky idea.
Cartilage, in general, is highly resistant to invasion by tumor cells,
so maybe there's some cartilage- derived anti-invasion factor?
Less interesting alternative explanations are that it's just hard for the cancer
to penetrate the cartilage, or perhaps because of the poor blood supply
in cartilage, cancer doesn't consider it particularly fertile ground.
But maybe that lack of blood vessels in cartilage can be exploited.
The reason that no blood vessels end up in cartilage is because
cartilage cells produce angiogenesis inhibitors,
blood vessel creation inhibitors.
And so maybe we can starve tumor growth by infusing these cartilage factors.
What scientists do is implant tumors into the eyeballs of rabbits,
so they can visualize how many blood vessels the tumor is able to draw to itself.
And indeed, shark cartilage contains inhibitors of tumor angiogenesis.
Such findings made the sales of shark cartilage skyrocket,
driving two shark species to the brink of extinction.
But cow cartilage does the same thing.
Here, they used bovine cartilage.
And so does human cartilage, for that matter.
So why sell shark cartilage?
Well, it does sound so much more exotic,
and sharks have like 10 times more cartilage per animal.
One 20-foot shark could net like 50 pounds of cartilage.
Just because cartilage has blood vessel inhibiting chemicals in it, though,
doesn't mean if cancer patients eat it, it will help them.
It's kind of like magical thinking: shark cartilage stops blood vessel growth,
thus, by consuming shark cartilage, humans will somehow be protected.
I mean, the shark cartilage protein molecules would seem to be
too large to be absorbed by the gut.
It's not like you're injecting shark cartilage into your bloodstream through an IV.
But there was this rat study that did find that
just feeding shark cartilage to the animals,
you could cut down on blood vessel growth within their bodies.
OK, but does that translate out to stopping the growth and spread of cancer?
Apparently not, as none of the shark cartilage doses tested
had any retarding effect on cancer growth or spread in tumor-bearing mice,
but just because it doesn't work in rodents doesn't mean it doesn't work in humans.
To find that out you need to put it to the test,
evaluating shark cartilage in human cancer patients, which we'll cover next.
When it comes to marketing unproven cancer treatments,
the Internet has become the Wild West.
Fraudsters are able to take advantage of people like never before.
"Cancer Patients Find Quackery on The Web," bemoaned the National Cancer Institute.
Did you know there were more than 200,000 documents
about cancer on the web?
What? When was this published? Oh, 1996.
That's just a few years after the web was born.
Not to worry, though, said the author of Dr. Linden's Guide to Online Medicine.
It takes a lot of time and money to maintain a Web page.
So don't worry, the mass of information on the Internet will dwindle
during the next few years as the Internet matures.
Right! Yes, dwindling from 200,000 down to a mere quarter of a billion.
And one the most commonly recommended "alternative cancer cures"
on popular websites is shark cartilage.
Much has been made in recent years of the mystical aura afforded to the stuff.
Clearly part of it is the visceral fear of cancer, combined with a healthy respect
for a creature that's survived basically unchanged since prehistoric times.
It has been reported that sharks rarely get cancer,
and their skeleton is made out of cartilage,
and so logic has led some to believe
that this must be the reason for sharks' relative health.
Not exactly sure that's logical, but they do have a lot of cartilage.
Cartilage, in general, has few blood vessels,
and blood vessels are important for cancer growth,
and all this conspired to prime fraught cancer patients for shameful exploitation
by pseudoscience and the supplement industry
with the addition of just one myth, and that's sharks don't get cancer.
But they do get cancer, after all.
Just another layer of fallacious arguments,
successfully convincing desperate cancer patients to buy ineffective products.
But wait, you don't know if it's ineffective until you put it to the test.
Sixty patients with a variety of advanced cancers, given like a dozen scoops a day
of shark cartilage, and not a single, even partial, response
was noted in any of their tumors.
Ineffective with no salutary effect on the quality of life.
In fact, suffering significant gastrointestinal toxicity from the stuff,
all the while the tumors progressed in all the patients.
But what's missing from this survival graph?
What happened in the control group?
There was no control group.
So while this is what you'd expect to see in advanced cancer patients,
how do we know the cancers wouldn't have progressed even faster
without the shark cartilage?
That's why we need randomized controlled trials,
but there weren't any until the Mayo clinic stepped up.
A randomized, placebo-controlled, double-blind, clinical trial
for patients with incurable breast or colorectal carcinoma.
Data on a total of 83 patients were analyzed,
and there was no difference in survival between patients getting shark cartilage
versus those getting placebo, nor any suggestion of improvement in quality of life.
There was evidently a prostate cancer study, too.
Only 5 patients were even able to complete the study,
and in all five their cancers continued to progress unabated.
So unfortunately, the claims for the benefits of shark cartilage
are completely unsubstantiated
by any objective data from controlled clinical trials.
Not so fast, said supplement manufacturers.
Maybe these crude commercial shark cartilage powders just
don't have high enough levels of whatever active components there may be,
so cancer patients should instead be taking shark cartilage extract pills.
So the National Cancer Institute said fine,
we'll test that, too, just to make absolutely sure.
And so they funded a randomized, double-blinded, placebo-controlled trial
to put it to the test.
Unlike the other shark cartilage dietary supplement studies,
they used the purified extract, and the study outcome was unambiguous.
It failed.
The shark cartilage group lived 14 months, and the placebo group lived 15 months.
So no significant difference in survival
or to time to progression or tumor response rate.
So these clinical studies suggest
shark cartilage is not just an unproven cancer remedy,
but actually a well disproven one.
Yet despite the overwhelming evidence to the contrary such claims persisted.
For example, the huckster who started it all wrote a sequel, "Sharks Still Don't Get Cancer."
Perhaps the only cure for this myth is to spread the rumor
that cartilage from the noses of such quacks fights cancer, too.
Anyway, if you really wanted to eat angiogenesis inhibitors,
why sit down to a bowl of cartilage powder,
when you could just eat an apple, or drink green tea, or turmeric, or pomegranate,
berries and nuts, soybeans, flaxseeds, broccoli---
all of which have been shown to have anti-angiogenic effects.