Think
of your gut microbiome as an intestinal garden, teeming with trillions
of bacteria, viruses and fungi that play a crucial role in your health.
Whether
the beneficial microbes in your gut are flourishing or getting crowded
out by unwelcome guests largely depends on how well you’re taking care
of them.
Here’s a guide to the busy world of “biotics” that inhabit your gut, and how to care for them.
The word “biotic” refers to “life” or living organisms. Probiotics
are live microbes — including bacteria and fungi — that have beneficial
effects on your health. Think of probiotics as the seeds that you
sprinkle on soil: With proper care, they’ll turn into flowers that
beautify your garden, repelling pests and crowding out weeds.
Probiotics
help metabolize your food and produce vitamins, fatty acids, and other
nutrients. They regulate your immune system, lower your risk for Type 2
diabetes and other chronic disease, and prevent the bad guys from
colonizing your gut.
Among
the most well-known probiotics are bifidobacteria. These bacteria
colonize our digestive tracts as soon as we’re born. We get them from
our mothers during delivery and through breast milk.
Another
common probiotic, lactobacillus, is found in many fermented foods.
Lactobacillus and bifidobacterium are just two of the many different
types of bacteria that inhabit our intestinal gardens.
How do I increase probiotics in my body?
Probiotic
supplements, which come in the form of capsules, gummies, powders, and
pills, are immensely popular, but they shouldn’t be your first choice.
While they may help certain people, studies show
they can also crowd out the wrong microbes. In general, a better way to cultivate your gut garden is to eat plenty of fermented foods and fiber-rich plants.
In
one recent study, Stanford researchers found that assigning people to
eat fermented foods every day for 2½ months reduced their inflammation
and increased their gut microbiome diversity. Higher levels of
microbiome diversity are associated with better health and lower rates
of disease.
Examples of fermented foods include the following:
- Kimchi and sauerkraut.
- Kombucha, a fizzy sweet and sour drink made with tea.
- Fermented dairy products like yogurt, kefir and cottage cheese.
- Tempeh, natto, miso and other fermented soy products.
- Some cheeses, like gouda and gruyère. You can identify
cheeses that contain probiotics by looking for phrases like “live
cultures” or “active cultures” on their labels.
Think of prebiotics like fertilizer for your microbiome. A prebiotic is typically a high-fiber
food.
The trillions of microbes that live in your gut depend on you for sustenance: Every time you eat, you’re feeding them too.
“If
probiotics are the good guys, then prebiotics are the foods that
promote the good guys,” says Erica Sonnenburg, a senior research
scientist in microbiology and immunology at Stanford University.
Prebiotics
consist mainly of complex carbs and fibers found in a variety of
different plant foods. When you eat fruits, vegetables, whole grains,
and other plants, much of the fiber they contain passes through your
stomach and small intestine relatively intact because humans lack the
enzymes to break it down. But the microbes in your large intestine can
metabolize fiber and break it down into other compounds.
The
way to promote lots of different friendly bacteria is to feed them lots
of fiber and prebiotics, says Chris Damman, a gastroenterologist at the
digestive health center at the University of Washington Medical Center.
How can I eat more prebiotics?
- Vegetables such as asparagus, onions, garlic, shallots, leeks, cabbage, peas, tomatoes, Jerusalem artichokes and chicory.
- Chickpeas, lentils, kidney beans and soybeans.
- Whole grains such as oats, barley, rye, wheat and corn.
- Fruits like apples, berries, bananas, grapefruits and watermelon.
- Almonds, pistachios, cashews, and other nuts and seeds.
Prebiotic supplements aren’t typically recommended. One
small study found
suggested that a prebiotic supplement called inulin at low doses was
likely good for health, but that consuming more than 20 grams of it
daily could be harmful. They also pointed out that the “health effects
vary among individuals.”
Some marketers are selling prebiotic beverages, but nutrition experts say there’s no strong evidence that they work.
Your
gut microbes break down high-fiber foods. The waste products this
process leaves behind are called postbiotics. These compounds include a
wide range of new compounds including vitamins, enzymes and amino acids.
“There are thousands and thousands of compounds that they’re making,” says Damman.
When
you feed your gut microbes prebiotics, they transform them into a group
of postbiotic compounds called short-chain fatty acids, which are
exceptionally good for your health.
One
of the most well-studied short-chain fatty acids is butyrate. This
compound helps to maintain gut health because it serves as a source of
fuel for the cells that line your colon. Butyrate helps to
reduce inflammation and
mediate the immune system.
It influences brain health and can stimulate the production of GLP-1, a
hormone that reduces appetite, says Damman. (Ozempic and Wegovy, the
popular weight loss and diabetes drugs, work by mimicking the action of
GLP-1.)
“Butyrate
is maybe the superpower of the microbiome,” Damman says. “It’s one of
the key things that it’s producing that is critical in all aspects of
our health.”
Postbiotics
are created during the digestive process as your gut microbes break
down fiber. One of the fascinating things about postbiotics is that the
compounds that one species of bacteria produces can be the food — or
prebiotic — that another species of bacteria depends on.
“It’s
cyclical,” Damman says. “You have this web of many players, and in this
community they’re both depending on one another and providing
sustenance for each other.”
What can I do to increase postbiotics in my body?
Fermented
foods contain postbiotics like lactic acid (yogurt) and acetic acid
(kombucha), and these compounds have been shown to confer health
benefits.
Coffee,
chocolate and some teas don’t contain live bacteria, but they do
contain postbiotics, which may be part of their healthful effects,
Damman says.
“We’re
still trying to tease this all apart,” Sonnenburg says. “If it turns
out that lactic acid, for example, is the part that’s most important
than all these probiotic pills that people are taking may be missing the
most active component of fermented food. That’s why we tell people it’s
better to just eat the fermented food.”
We’ve
talked a lot about friendly bacteria, but there are plenty of
pathogenic bacteria that cause deadly infections. The best line of
defense against harmful bacteria are
antibiotic medications, which kill off bacteria or make it difficult for them to grow and multiply.
Antibiotics were one of the great discoveries of the last century. They’ve saved many lives and
made it possible for doctors to pioneer medical procedures like open-heart surgery and organ transplants.
Experts say the introduction of antibiotics a century ago helped to extend the average human life span by 23 years.
But
one downside of antibiotics is that they kill both the harmful and
friendly bacteria in your gut. Think back to the lawn analogy. If you’ve
got a bunch of weeds growing all over your lawn, you may have to use an
herbicide and destroy some of your grass and plants in the process — so
you can clear space for new grass to grow.
If
you have a bacterial infection, taking an antibiotic will kill off the
bad microbes and perhaps sacrifice some good ones in the process.
Should I use a probiotic to counter the effects of antibiotics on gut health?
Many
people who take a course of antibiotics combine it with a probiotic
supplement, hoping that the supplement will protect or restore their
communities of good gut microbes.
But
research suggests that it’s better to eat fermented foods instead or
let your gut recover on its own rather than taking a supplement.
In one study,
the microbiomes of people who took a probiotic while using antibiotics
took far longer to recover. While probiotic supplements are very useful
for specific conditions — like irritable bowel syndrome, traveler’s
diarrhea and inflammatory bowel disease — there are
more reliable ways to nourish your gut microbiome.
The
way to promote lots of different friendly bacteria is to feed them lots
of fiber and prebiotics, Damman says. “It all comes back to diet,” he
added. “Diet is not the only thing, but it’s a big thing — and the
problem for a lot of people is that they’re not eating the right foods.”
Do you have a question about healthy eating? Email EatingLab@washpost.com and we may answer your question in a future column.
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