A RECENT study, mice were cured of depression and anxiety with
probiotics. This was one of a long string of recent findings
about probiotics showing that beneficial bacteria can improve
conditions such as allergies, asthma, stomach ulcers, bad breath,
tooth decay, IBS, cancer, cholesterol levels, bone density, cardiovascular
disease, and now mood disorders.
How is it possible for anything to influence
so many systems of your body? The reasons are complex. But lets
start with some basic facts about probiotics.
1. Probiotics are bacteria and yeasts that
live primarily in your intestines and are good for you.
2. You have a lot of them. If you were
able to pull them all out of your body, you would have about
a quart of bacteria and yeasts, and it would weigh almost three
pounds more than your heart, kidneys, and pancreas combined.
3. Probiotics are usually much smaller
than our own cells, but we have ten times as many. Your body
is made up of about 10 trillion cells. But you have about 100
trillion microbes living in and on your body.
4. Without that quart of probiotics, you
would be unhealthy. To function properly, your immune system
relies on those bacteria and yeasts.
The study on mice fascinated me. It reminded
me of an earlier study done with humans showing that people who
took probiotic supplements felt less stressed and had less anxiety
and depression than people who had taken a placebo.
In the more recent study, researchers took
normal mice, which are usually fairly timid (staying close to
walls when they explore, and being reluctant to walk in the open).
They fed half the mice a brew containing a particular strain
of gut bacteria Lactobacillus rhamnosus (a strain
found in some yogurts and probiotic supplements) and the
mice became less timid; they explored more freely.
And when the researchers put the mice under
stress (by plunging them in water, for example), the probiotic
mice were less stressed than normal mice (the stress hormones
in their blood didnt rise as much in response to the stress).
You can read more details about the study here and here.
But the researchers wondered how a bacteria
in the gut could alter the mice psychologically.
So they cut the vagus nerve the bundle of nerve fibers
that connect the guts and the brain and sure enough, this
stopped the positive effects of the probiotics.
So somehow the bacteria did something to
the mice guts that sent a signal to the brain, causing the mice
to feel (or at least behave) less anxious and depressed, and
to produce less stress hormones.
The pathways for the other positive effects
of probiotics on allergies, heart disease, etc.
are at least as complex. For example, you have several kinds
of white blood cells. One kind either calms down an inflammatory
reaction in the body or inflames it. For the most part, it is
in your intestines where these cells learn which kind of cell
they should become.
In other words, depending on what they
encounter in your intestines, they will become calmers or inflamers.
If you have probiotic bacteria (rather than the bad kind), more
of those white blood cells become calmers, and they then circulate
in your bloodstream and prevent immune system overreactions like
chronic inflammation to the inside of your arteries, for example,
or rheumatoid arthritis, allergies, asthma, etc.
I dont want to get too bogged down
in technicalities here. If youd like to know more detail
about how the immune system works and how probiotics play a crucial
part, I highly recommend a book by Gary Huffnagle, PhD: Probiotics Revolution.
Huffnagle is one of the leading probiotic
researchers making new discoveries in this burgeoning field of
research. He and a colleague were the first to create human-like
allergies in mice using antibiotics. They were trying to answer
the question: Why do more and more people have allergies and
asthma in the last fifty years? If you look at the statistics,
it looks like a rapidly growing epidemic. Whats going on?
Researchers discovered that the trend coincides
with the use of antibiotics, which began to be used widely in
the 1950s, and there are many good reasons to suspect that
antibiotic use and the rise of allergies and asthma are directly
As you probably know, when you take antibiotics,
they kill harmful bacteria, but they also kill beneficial bacteria
(probiotics). After youre done with a round of antibiotics,
your intestines will slowly try to come back to their former
balance, but in our pasteurized, sterilized world, this is more
difficult than it used to be. And besides, antibiotics dont
kill everything. They hardly affect yeast, which is usually only
about one percent of our intestinal microbe population. But with
its bacterial competition out of the way because of the antibiotics,
yeasts can flourish. They and unfriendly bacteria more resistant
to antibiotics can establish themselves, making it difficult
for your intestinal flora (bacteria and yeast) to return to normal,
even though there are usually plenty of bacteria and yeast in
the air, which lands on our food and we eat it (this is how probiotics
naturally wind up in our guts once we are no longer breastfeeding).
But the more rounds of antibiotics we endure,
the more out of balance our intestinal ecosystem can become,
and this lack of microbial balance can create problems
problems that can be solved by deliberately re-introducing beneficial
bacteria (probiotics) into your diet.
There are several other things that contribute
to an imbalance in our bacteria. Most important (besides antibiotics)
is what we eat. Sugar selectively feeds harmful bacteria. Fiber
selectively feeds beneficial bacteria. So as our diet has changed,
the kinds of bacteria living in our guts have changed too.
We also aren't exposed to as many bacteria
as we once were because of chlorine in our drinking water, antibacterial
soaps and hand gels, etc.
This means if you want to have a healthy
microflora, you're going to have to take deliberate steps to
make it happen.
first do no harm
If you have a problem and you suspect probiotics
may help, one of the best things about trying probiotics is that
it can't hurt. If you eat probiotic-rich foods like yogurt
and kefir and sauerkraut and it has no effect on your problem,
you have not harmed yourself in any way. So it is certainly worth
One of the immediate side effects of probiotics
(and the only downside) is gas. The bacteria eat carbohydrates
and fiber, and when they do, they produce hydrogen and methane.
The good news is that there are also bacteria
that feed on hydrogen and methane! So if you continue to eat
probiotics, after a few weeks the gas problem will disappear
because the number of gas-eating bacteria rises until they are
eating all the gas you are producing.
And speaking of feeding the bacteria, the
other part of increasing the number of good bacteria in your
intestines is to eat the right foods. Certain foods (like sugar,
white flour, and white rice) selectively feed bad bacteria, while
other foods, like beans, whole grains, and fruit, selectively
feed probiotic bacteria.
So to give your probiotics a chance to
flourish in your guts, you should not only eat foods containing
probiotic bacteria, you should also eat PREbiotic foods (food
that contains the kind of stuff probiotic microorganisms like
to eat). Ill have a list of both kinds of foods later in
But first, here are a few interesting facts
1. Almost all the microbes in our intestines
are bacteria, and there are many different kinds: Somewhere between
500 and 1000 separate species.
2. Most bacteria we are exposed to are
either good for us or neutral. Very few bacteria are actually
bad for us.
3. All living creatures have bacteria living
in them. This includes fish, insects, birds and mammals.
4. Bacteria live in water everywhere on
earth, and in dirt. There are over a hundred million bacteria
living in a single teaspoon of rich soil.
5. Probiotic bacteria can digest fiber.
Harmful bacteria typically cannot.
6. Some kinds of harmful bacteria and yeasts
thrive on sugar.
7. One of the ways probiotics help is by
competing with bad bacteria. For example, the bacteria that cause
cavities (Streptococcus mutans) and gum disease (Porphyromonas
gingivalis) are kept low by eating probiotic foods. The same
is true with the bacterium that causes stomach ulcers (Helicobacter
pylori). When you eat probiotic food, the beneficial bacteria
compete with harmful bacteria and keep them from getting the
8. Probiotic bacteria are so important,
breast milk contains probiotics and prebiotics.
Probiotics are an important factor to consider
in your diet. The number of studies on probiotics worldwide has
exploded in the last fifteen years, and the things researchers
are discovering are nothing less than revolutionary.
One interesting possibility, for example,
is that the epidemic of obesity may have some relationship with
gut bacteria. In one of the many experiments done with probiotics,
obese adults reduced their food intake by 500 calories a day.
Half of them included yogurt in their diet (six ounces three
times a day) and the other half ate a different dessert with
no probiotics but with the same number of calories.
Twelve weeks later, they were all tested,
and all had lost weight.
But the yogurt eaters lost thirty percent
Coming from a different angle, the livestock
industry has found that if they add a low dose of antibiotics
in the feed (keeping the number of microbes in the livestock's
intestines low), the animals gain significantly more weight
on the same amount of feed.
Whatever your reason for interest in probiotics,
it is worth the experiment to try raising the number of beneficial
bacteria you eat and see what happens. With that in mind, below
are two lists; one is a list of foods containing live probiotic
bacteria, and one is a list of prebiotics foods that selectively
feed probiotic bacteria already in your guts.
top probiotic foods
This is the most well-known probiotic food, and the one that
first awakened scientists to the possibilities of probiotics
potential. A Nobel Prize-winning immunologist, Ilya Mechnikov
studied the famously long-lived peasants of Bulgaria in the early
1900s and discovered that there was something unique about
their diet, which he attributed to their longevity: They ate
a lot of fermented food, including yogurt.
There are many different kinds of yogurts,
and they contain different combinations of bacteria. Each kind
of bacteria may be important, so your best bet is to eat different
kinds of yogurt regularly. Also make sure the yogurt you choose
has live, active cultures because some yogurt makers
ferment milk into yogurt with bacteria but then pasteurize it
(heat it up to kill the bacteria), which defeats the probiotic
purpose of yogurt.
And one other thing: Try not to eat sugary
yogurt. If you want some sweetness and flavor, see how little
sweetness you can get by with. Just add fruit without sweetener
or buy the sweet kind but also buy plain (unsweetened) yogurt
and mix them.
This is a cultured milk that tastes somewhat like a liquid yogurt,
but with a great many more different kinds of bacteria than yogurt,
and also containing some yeasts. It is easily made at home (and
it will cost a lot less if you do). Learn more about kefir here
3. Sauerkraut and kimchi. Both of these are fermented cabbage. Kimchi has
the added flavor of other vegetables and spices. But with these
products, you must find versions with live, active cultures.
Usually these will be in the refrigerated section of a health
food store. You can also make your own inexpensively. Learn about that here.
4. Fermented pickles and tomatoes. Also in the refrigerated section.
Sometimes fresh live cultured foods can
be expensive. To find out how to make probiotic foods at home
for less, I heartily recommend the book, Wild Fermentation.
top prebiotic foods
Below is a list of foods that have substances
in them that selectively feed probiotic bacteria and simultaneously
help to starve harmful bacteria in your guts:
7. Whole oats
9. Whole wheat
11. Red wine
Caring for your own intestinal ecosystem
could benefit you in many ways. I believe that we're only just
scratching the surface so far. But there is no reason to wait
until all the results are in. Healthy people have been eating
probiotic and prebiotic foods for a very long time with no negative
side effects, and probably gaining many benefits along the way.
You can start your own experiment with your guts right away and
see just how healthy you can become.
In the book, Probiotics Revolution is a list of which
bacteria have been shown to benefit which ailments. And also
a good list of which supplements are the most reliable.