How the food you eat affects your gut - Shilpa Ravella

View full lesson: http://ed.ted.com/lessons/how-the-food-you-eat-affects-your-gut-shilpa-ravella

The bacteria in our guts can break down food the body can’t digest, produce important nutrients, regulate the immune system, and protect against harmful germs. And while we can’t control all the factors that go into maintaining a healthy gut microbiome, we can manipulate the balance of our microbes by paying attention to what we eat. Shilpa Ravella shares the best foods for a healthy gut.

Lesson by Shilpa Ravella, animation by Andrew Foerster.

Trillions of bacteria, viruses, and fungi
live on or inside of us,

and maintaining a good, balanced
relationship with them

is to our advantage.

Together, they form the gut microbiome,

a rich ecosystem that performs a variety
of functions in our bodies.

The bacteria in our guts
can break down food the body can't digest,

produce important nutrients,

regulate the immune system,

and protect against harmful germs.

We don't yet have the blueprint

for exactly which good bacteria
a robust gut needs,

but we do know that it's important
for a healthy microbiome

to have a variety of bacterial species.

Many factors affect our microbiomes,

including our environment,

medications like antibiotics,

and even whether we were delivered
by C-section or not.

Diet, too, is emerging as one
of the leading influences

on the health of our guts.

And while we can't control all
these factors,

we can manipulate the balance
of our microbes

by paying attention to what we eat.

Dietary fiber from foods like fruits,
vegetables, nuts, legumes, and whole grains

is the best fuel for gut bacteria.

When bacteria digest fiber,

they produce short chain fatty acids
that nourish the gut barrier,

improve immune function,

and can help prevent inflammation,
which reduces the risk of cancer.

And the more fiber you ingest,

the more fiber-digesting bacteria
colonize your gut.

In a recent study, scientists exchanged
the regular high-fiber diets

of a group of rural South Africans

with the high-fat, meat-heavy diets
of a group of African-Americans.

After just two weeks on the high-fat,
low-fiber, Western-style diet,

the rural African group showed
increased inflammation of the colon,

as well as a decrease of butyrate.

That's a short chain fatty acid thought
to lower risk of colon cancer.

Meanwhile, the group that switched
to a high-fiber, low-fat diet

had the opposite result.

So what goes wrong with our gut bacteria
when we eat low-fiber processed foods?

Lower fiber means less fuel
for the gut bacteria,

essentially starving them
until they die off.

This results in less diversity

and hungry bacteria.

In fact, some can even start to feed
on the mucus lining.

We also know that specific foods
can affect gut bacteria.

In one recent microbiome study,

scientists found that fruits,

vegetables,

tea,

coffee,

red wine,

and dark chocolate

were correlated with
increased bacterial diversity.

These foods contain polyphenols,

which are naturally occurring
antioxidant compounds.

On the other hand,

foods high in dairy fat,

like whole milk, and sugar-sweetened sodas

were correlated with decreased diversity.

How food is prepared also matters.

Minimally processed, fresh foods
generally have more fiber

and provide better fuel.

So lightly steamed,

sautéed,

or raw vegetables

are typically more beneficial
than fried dishes.

There are also ways of preparing food
that can actually introduce good bacteria,

also known as probiotics,
into your gut.

Fermented foods are teeming
with helpful probiotic bacteria,

like lactobacillus

and bifidobacteria.

Originally used as a way
of preserving foods

before the invention of refrigeration,

fermentation remains a traditional
practice all over the world.

Foods like kimchi,

sauerkraut,

tempeh,

and kombucha

provide variety and vitality
to our diets.

Yogurt is another fermented food that can
introduce helpful bacteria into our guts.

That doesn't necessarily mean that
all yogurt is good for us, though.

Brands with too much sugar
and not enough bacteria

may not actually help.

These are just general guidelines.

More research is needed before
we fully understand

exactly how any of these foods
interact with our microbiomes.

We see positive correlations,

but the insides of our guts are difficult
places to make direct observations.

For instance, we don't currently know

whether these foods are directly
responsible for the changes in diversity,

or if something more complicated
is happening.

While we're only beginning to explore
the vast wilderness inside our guts,

we already have a glimpse of how crucial
our microbiomes are for digestive health.

The great news is we have the power
to fire up the bacteria in our bellies.

Fill up on fibers,

fresh and fermented foods,

and you can trust your gut
to keep you going strong.