And free radicals aren't always bad for you.
By Sara Chodosh June 27, 2019
Vitamin E might make lung
cancer spread faster—that's probably something you never expected to hear.
We're used to the message that vitamins are good for us. But actually, the
latest news about lung cancer isn't all that new. Researchers have known for a
while that certain antioxidants seems to increase cancer risk, ever since a 1996 clinical trial had
to be halted after patients receiving beta-carotene had markedly higher lung
cancer rates. Now, a new
study in the journal Cell has sussed out
exactly how antioxidants—which most of us think are supposed to be
healthy—could contribute to cancer risk.
Even if you’ve only seen
the word on the side of a blueberry box, you’ve heard of antioxidants. It’s a
lot less likely that you have a solid grasp on what they actually are. The
companies selling us antioxidants, whether they be produce distributors or
supplement stores, have drilled home the basics: antioxidants help fight free
radicals. What are free radicals? They’re bad, and that’s all you really need
to know.
Except, of course, that's
not all you need to know, because antioxidants and free radicals are a lot more
complicated than most people ever realized. When researchers first
brought them to public attention in the 1990s, it was because early
evidence suggested that free radicals contribute to everything from hardened
arteries to cancer. More importantly, people who ate low levels of antioxidants
seemed to be at higher risk for developing those same conditions. The food and
supplement industries took that early research and ran with it: we needed more
antioxidants in our lives.
But since the '90s, the
actual scientific evidence about antioxidants hasn't been nearly as cut-and-dry
as cereal boxes might lead you to believe. In a lot of cases, yes, antioxidants
are a positive contribution to your diet—but it some cases, too many can
actually cause the very diseases we're trying to prevent.
What is
an antioxidant?
An antioxidant, at
least when we're referring to the nutritional side of things, is any molecule
that can act as an electron donor. Feel like you're back in high school chemistry
yet? It's not actually complicated: a free radical is just any molecule with a
lone electron in an outer electron shell. Bear with us for a second, because
yes, this is a lot of chemistry jargon, but it's important in order to
understand what's really going on inside your body.
Electrons whiz around in
little clouds around atoms (which are the little tiny building blocks of matter
that make up everything but the void), and they vastly prefer to do that in
pairs. Sometimes, though, something happens that takes an electron away from
its partner—that’s how you get a free radical. It’s just an atom or a molecule
with a lone, rogue electron. The problem is that solitary electrons are
incredibly reactive, because they’re constantly trying to get another electron
to come join them. They'll do anything to get a buddy, which means free
radicals can do a lot of damage inside your body. Stealing electrons from other
molecules, whether they be DNA or proteins, alters those structures and
therefore alters their function.
Antioxidants perform the
crucial function of donating an electron to a free radical, effectively
neutralizing it. Sounds pretty positive, right? And mostly, it is. We'd
quite literally die without them. But here's the thing:
Wait, why
do we need free radicals?
Sometimes, your body has to
kill things. Most of these things are bacteria, viruses, and other invaders,
but sometimes it also has to take out your own cells. As they divide, cells
accumulate mutations and can start to act funny. Ideally, before they turn into
something serious like cancer (which is just cell growth gone haywire), your
body kills them. The ways in which your immune system attacks both its own
cells and foreign microbes are hugely varied, but free radicals are one weapon
in the arsenal. Your immune system is essentially harnessing their destructive
power for good. When you get a cut on your finger, one crucial step your body
takes to prevent infection is to produce more free radicals in the area. Almost
all inflammation in your body involves free radical production, which is one
reason that chronic inflammation can lead to a variety of diseases, especially
cancer. Over time, that exposure to DNA-damaging molecules results in
mutations, and those mutations can accumulate to make a cell cancerous. But in
small doses, free radicals are crucial.
In fact, there are inherited diseases in which
people can't produce certain types of free radicals, and they're
often diagnosed when young patients keep getting life-threatening infections
from seemingly innocuous sources. They can't fight off the invaders effectively
without these reactive molecules.
Because you need free
radicals to function properly, your body produces its own antioxidants as well
as recruiting some from your food to keep their numbers in check. But
crucially, it maintains a balance. A lot of marketing primes us to think of
antioxidants like water-soluble vitamins—you can’t have too many, so take ‘em
just in case. Early research may have suggested that, but as biologists learn
more about antioxidants it’s
How can
you have too many antioxidants?
There’s still a lot we
don’t understand about this field, but preliminary research suggests a few ways
having too many antioxidants can hurt us.
One has to do with that
balance we talked about: You need a certain supply of reactive molecules in
order to maintain your immune system. Plus, researchers are now realizing that
some signaling pathways inside cells are only activated by free radicals. If
you’re loading up on antioxidant supplements, you might be throwing your body
out of whack and preventing it from doing its job.
Increasing evidence suggests that
lung cancer and certain types of melanoma are actually made worse by
excess antioxidants. That seems to be because free radicals are, in some ways,
actively protecting cells from becoming cancerous. If you've got too many
antioxidants, they start interfering with those anti-tumorigenic
Exercise also seems to rely
somewhat on some free radicals to induce a little cellular stress. Preliminary
studies now show that
taking high levels of antioxidants interferes with the health benefits you get
from exercise.
If all of this seems
incredibly counter to what you’ve just learned, don’t worry—it felt that way to
scientists, too. It’s all quite complicated and still poorly understood, but
the most important thing to realize is that we talk about “free radicals” and
“antioxidants” as big groups, when really they’re quite diverse. There are many
types of both molecules, and each seems to act in a slightly different
capacity. Vitamins E and C, for instance, are both antioxidants, but they seem
to fill different roles in your body. So just getting more antioxidants as a
broad category is kind of meaningless.
What's more, you actually seem to need a
mixture of antioxidants, not just more of one kind.
When antioxidants donate
that crucial electron, they're sometimes left with their own lonely electron.
Now they can behave like a free radical. Fortunately, other antioxidants can
come along to help them out, and then yet more antioxidants can help those ones
out, and so on—it's a cascade in which they can all help stabilize each other.
Whole foods contain that
balance of antioxidants, but when you take a pill of, say, vitamin E, you’re
only getting that one molecule. That might be part of why taking supplemental
forms of antioxidants doesn’t seem to help prevent diseases.
Hold on,
antioxidants don't prevent disease?
We know that people who eat
foods rich in antioxidants tend to be healthier, which is where this whole
craze came from in the first place. Part of that is undoubtedly that folks who
eat lots of fruits and veggies (your primary source of antioxidants) also tend
to have other healthy habits (and tend to be wealthier and whiter, both of
which are big factors in your health). Plus, those fruits and veggies are good
for you for other reasons, like their high-doses of fiber and lack of processed
ingredients.
But it’s also true that you
do need a certain supply of antioxidants, which your body is excellent at
extracting from whole foods. Getting a sufficient amount from your diet is
definitely an important part of staying healthy—but that doesn't mean more is
better.
There have been multiple huge studies examining
whether antioxidant supplementation was associated with decreased risk of
everything from cancer to stroke to heart disease, and they've pretty much all found that it didn't matter. Unless you have a
deficiency in a particular antioxidant, taking a supplement doesn't help you. And
in the case of lung cancer and melanoma, it could hurt. Yet again, the truth is
that there's no magic ingredient or behavior that will make you healthy: eating a balanced diet and being as active as you can is the
best way to lower risk of disease.
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