Here at SciShow, we know how to stay on top
of the truth. So when there are misconceptions about science
-- especially ones that seem plausible -- we try to help clear things up. And one topic that generates a lot of myths
is … cancer. We’re not talking conspiracy theories here
-- we’re going to focus on things that sound like they could be true, and talk about why
they aren’t. Things like: Do sharks get cancer? If you
have cancer, is it okay to eat sugar? What about superfoods? And are cancer rates rising
so fast that we’re all going to get it? A lot of these misconceptions have a tiny
bit of real science at the core -- they’ve just been misinterpreted. Studies done in the 70’s sparked interest
and created the myths that sharks don’t get cancer, and taking shark cartilage supplements
will cure or prevent cancer. One study, by researchers at Johns Hopkins,
found that certain chemicals in cartilage -- that squishy white connective tissue -- could
prevent blood vessels from forming. Cancer researchers are super interested in
targeting this process, called angiogenesis, because tumors need a supply of blood. Cut
off the blood supply and you could theoretically starve the tumor. Around the same time, researchers in another
study fed sharks a nasty, normally cancer-causing chemical called aflatoxin B1, waited a while,
and didn’t see any tumors. But just because you don’t see something
happen one time doesn’t mean it won’t happen ever, and if the researchers had waited
longer the sharks probably would have developed cancer. But since sharks have skeletons that are basically
made of cartilage, shysters saw their chance and started selling supplements made from
shark cartilage. Some people figure that if shark cartilage
contains some chemical that prevents blood vessel formation, that chemical should also
be in supplements made from shark cartilage. There are a few problems with this. First,
life isn’t a video game. You can’t just eat something to gain its power! No matter
how much Star Wars mac and cheese you eat, you won’t turn into a Jedi. It doesn’t make any sense that just eating
tissue from an animal that doesn’t get cancer would pass that benefit on to you. It’s true that cancer doesn’t tend to
invade cartilage, and some of the chemicals responsible for that effect are being tested
as cancer drugs. But those can be made artificially. Anyway, there’s definitely not enough of
those active ingredients in bulk shark cartilage supplements to have any benefit. Multiple
studies have shown that. Also: sharks DO get cancer! In the years since
those earlier studies, scientists have found sharks in the wild with tumors. They’re not necessarily easy to find -- for
one thing, sharks with cancer probably don’t live long enough for researchers to bump into
them. So if sharks do get cancer less often than other animals, we might have a hard time
finding out for sure. But it definitely happens. Here’s another thing people sometimes tell
cancer patients about their diets: If you have cancer, the misconception goes, you should
avoid eating sugar. The advice might be well-intentioned, but
it’s also wrong -- and based on misinterpreted science. The idea is that cancer cells really like
making energy in a way that requires a lot of sugar. Most of the time, whenever there’s oxygen
around, healthy cells use that oxygen to convert glucose sugar into energy. It’s efficient enough that most of the energy
from the sugar is converted into a form the cell can use. If there isn’t enough oxygen, cells can
use a different process to get some energy from sugar -- but not nearly as much. It’s wasteful, and it’s usually not the
cell’s first choice … unless it’s a cancer cell. In 1924, a German scientist named Otto Warburg
noticed that cancer cells will go for option B even if they don’t have to. Which means
that they need a lot more glucose to make the same amount of energy. We’re still not exactly sure why this benefits
the cancer cells, but it might help them grow even when the body tells them not to. From this, people seem to conclude that since
cancer likes sugar, you shouldn’t eat sugar. That’s not such a far-fetched idea, and
at least one or two studies have tried it, but … not eating sugar doesn’t actually
seem to give cancer cells access to less glucose. Here’s the thing: To your body, a calorie
from sugar is more or less indistinguishable from a calorie from protein. No matter what
you eat, your body is eventually going to convert it into glucose. So restricting the sugar you eat isn’t going
to do much to affect a tumor -- it’ll get the sugar anyway. Those same well-intentioned diet nannies who
tell you not to eat sugar will also say that taking a ton of antioxidants will prevent
cancer. If you believe the people who market green
tea and acai berries, antioxidants are the cure for what ails us, no matter what it is.
They’ll slow down aging in our cells and prevent them from turning cancerous. And, don’t get me wrong. Antioxidants are
important. Sometimes, destructive chemicals called reactive oxygen species get loose in
our cells. They damage crucial cellular machinery, including DNA. And … DNA damage can lead
to cancer. Antioxidants neutralize those reactive oxygen
species before they have the chance to do any harm, which is very nice of them! So you’d figure eating lots of them would
help prevent more damage. But, like with sugar, just because something
sounds like it makes sense doesn’t mean it actually does -- that’s why scientists
do studies to look for evidence. And there isn’t much evidence that taking
antioxidant supplements lowers the risk of cancer. It’s not for lack of trying. A bunch of
major clinical studies have followed people taking antioxidant supplements like vitamins
A and E and found very little benefit. It is still possible that certain kinds of
antioxidants might work -- these studies concentrated on purified supplements, and there’s a chance
those antioxidants could be better for you when they’re still in food form. Scientists
can’t say for sure yet. But antioxidants are still good for you, right?
Might as well load up on them anyway--it can’t hurt. Actually, if you already have cancer, it might
hurt. According to some studies, antioxidant supplements
might actually speed up the progression of cancer. For example, one recent study by Swedish researchers
found that melanoma -- a type of skin cancer -- spread more aggressively in mice that received
antioxidant supplements than in mice that didn’t. The reason seems to be that antioxidants can’t
tell the difference between healthy cells and cancer cells, and will do their jobs everywhere.
That leads to stronger, healthier cancer cells, too. In fact, those researchers think antioxidants
might even enhance a cell’s ability to travel around the body. Which, when it comes to cancer,
is very, very bad -- that’s how it spreads. Speaking of things that are supposed to be
good but might help cancer spread instead, let’s talk about biopsies. When doctors want to know if certain types
of tumors are dangerous, they sometimes use a needle to extract a tiny piece it. It’s a useful procedure, because it lets
doctors tell not only IF a tumor is cancerous, but how advanced it is. But some people worry that biopsies come with
an element of risk. If doctors are plunging needles into tumors,
won’t that dislodge the tumor cells and help them to spread? Again, it sounds pretty reasonable. One study
of several hundred breast cancer patients showed that about 30% of the time, biopsies
did shake loose bits of tumor. Sounds scary--but there’s a catch. How long the researchers waited before checking
back made a huge difference to how many displaced tumor chunks they found. The longer they waited,
the fewer rogue tumor cells there were. Which means that even though bits of tumor
got loose, after a while they just...died. When biopsies free tumor cells, those cells
aren’t usually designed for spreading and making more tumors. There are also techniques doctors can use
to minimize the spreading of tumor cells, like biopsy needles that include tiny vacuums. Overall, the risk of a tumor spreading as
a result of a biopsy is incredibly small, especially compared to how much information
doctors can get from those biopsies. There are some exceptions, though. Testicular cancer actually does have a decent
chance of spreading after a biopsy -- which is why doctors generally don’t do biopsies
on testicular cancer. If they think someone has a tumor, they’re
more likely to just remove the whole testicle. Now let’s talk about two misconceptions
when it comes to the current state of cancer in the world. The first is the idea that cancer
is a modern disease. It might sometimes seem like that’s the
case, because modern life is full of potentially cancer-causing stuff, and we hear about them
all the time. For instance, certain kinds of industrial
pollution and environmental contaminants can lead to cancer. And easy access to fatty, sugary, nutritionally
deficient foods contributes to obesity, which can also lead to cancer. Plus … tobacco. But even if we all returned to some pre-Industrial
Revolution pastoral lifestyle, cancer wouldn't just vanish. Lots of things that cause cancer have been
around as long as the human race, or longer. Things like ultraviolet radiation, wood smoke,
and genetics can all cause cancer, and they have nothing to do with our modern way of
life. Cancer has been found in three thousand-year-old
human remains. Even dinosaurs had tumors. The disease is way older than we are. Which leads us to a closely related myth:
Cancer is killing more people around the world. You might see kind of scary headlines, talking
about how more people are getting and dying from cancer. Others will say that those headlines are lying
and we’re all going to be fine. But, like so many things in life, the truth
is … complicated. There are a lot of factors here. For one thing,
the global burden of cancer--that’s the total amount of cancer in the world-- is shifting
from developed to developing nations. Meaning, in higher-income nations, rates of
cancer are mostly shrinking. But they’re rising in others. Secondly, death rates from cancer in the United
States are declining. We’re getting better at both prevention and treatment, so you’re
less likely to get cancer and more likely to get better if you do. That said, the total amount of cancer cases
and deaths is going up. That’s because, even though we’re getting
better at stopping cancer, and percentage-wise it’s decreasing … we’re living longer. Our standard of living has improved, so there
are more older people on the planet. People don’t die of childbirth or malnutrition
as much as our ancestors did. But the older someone gets, the higher their
risk of cancer -- their body simply has more time to develop it. And because the population of old people is
getting bigger, lots of those people will get and die from cancer. Basically, we’re winning the fight against
cancer, but we’re also winning other fights that mean people live long enough…to get
cancer. Thanks for watching this episode of SciShow,
which was brought to you by our patrons on Patreon. If you want to help support this
show, just go to patreon.com/scishow. And don’t forget to go to youtube.com/scishow
and subscribe!
this info isn't very good. I'm not going to parse it all but here's this:
https://www.oncologynutrition.org/erfc/healthy-nutrition-now/sugar-and-cancer/
It kind of does say sugar is bad if you have cancer.
And the antioxidant study he's referring to about mice to getting more cancer was a garbage study that got a ton of publicity. The study was using synthetic vit E (which doesn't work and might actually cause harm) and using completely wrong dosages.
Anyway I quit watching after the sugar bit.