Tell someone that they’re about to eat a substance that
started out as a vegetable but was then processed by bacteria and yeast into an
alcohol or acid, and you shouldn’t be surprised if they turn up their nose or
run away screaming. The thought of those little critters messing with perfectly
good food might sound more like a Transylvanian science experiment, complete
with lightning strikes, than a healthy and delicious part of your diet.
But that’s exactly what fermentation is. Humans have
harnessed and refined the process for a long time, and some of our favorite
healthy foods are the result of this legacy of experimentation.
What is Fermentation?
Fermentation is a way of preserving the
flavor, texture, and quality of food as well as enhancing shelf-life.
It’s a natural process through which microorganisms like
yeast and bacteria convert complex molecules into simple ones; for example
carbohydrates — like starch and sugar — into alcohol or acids. Through the
fermentation process, beneficial bacteria like probiotics are formed.
While some fermented foods can have strong odors (think bleu
cheese and sauerkraut), the process of fermentation is very different from
rotting, which is an uncontrolled decomposition leading to the growth of
dangerous bacteria and molds (and which, eventually, turns food into dirt).
While rot makes foods break down quickly, fermentation preserves them.
Types of Fermented Foods
There are many fermented foods at the grocery store, many of
which you’ve probably seen – and some of which you may already enjoy.
Some of the most common fermented foods include:
- Sauerkraut, which is a type of fermented cabbage
a fermented, effervescent tea that is often flavored
- Miso, a salty paste, usually made from soy, which is
often used for soup and flavoring bases
- Kimchi, a traditional spicy Korean food made with
cabbage and other veggies
- Pickled vegetables, like carrots, green beans, or
cucumbers (note that these are high in sodium)
- Yogurt, which can have probiotics added and be made
from dairy or from non-dairy milks based
on foods like cashews, almonds, coconut, peas, and soy (stick to
unsweetened varieties to avoid the high added sugar content of many
- Natto, a sticky food made from fermented soybeans
(and something of an acquired taste!)
a fermented dairy product that can also be made using non-dairy options
like cashews or almonds (check the label to see if they contain probiotic
- Kefir, a cultured probiotic food that can be made
from dairy, coconut, or water bases
And, in a slightly different category (because they’re
cooked, so the microbes are killed), we have:
- Tempeh, a fermented soybean cake
- Sourdough bread, which is made by the natural fermentation
of Lactobacilli and yeast
A Word About Alcoholic Fermentation
Alcoholic products, such as beer and wine, are also
fermented. However, the effects of alcoholic beverages on the microbiome are
quite different from the effects that other fermented foods offer. It’s true
that many fermented foods do contain a small amount of alcohol, as a natural
result of the fermentation process. But the quantity is minimal. For instance,
kombucha typically contains 0.5% by volume or less, a small amount that allows most
varieties to be labeled non-alcoholic.
When it comes to the microbiome, drinking fermented alcohol products
like beer can lead to gut inflammation, intestinal hyperpermeability, and
alcohol-induced oxidative stress. There’s a reason the word “intoxicated”
contains the word “toxic” – alcohol can kill microorganisms in our microbiome
in the same way it is used in medical practice to sterilize skin and needles.
On the other hand, fermented foods like kombucha, yogurt,
kimchi, or sauerkraut can have positive effects
on your microbiome, like improving your immunity, reducing how long you’re sick,
improving nutritional absorption, decreasing inflammation, and alleviating
upset stomach and diarrhea. While alcoholic beverages fall under the broad
category of fermented foods, for the purpose of simplicity this article focuses
on the fermented foods that have little or no alcohol.
5 Health Benefits of Fermented Foods
Why might you want to make fermented foods a part of your
regular diet? Here are five good reasons. Some of the probiotic-related studies
cited below have focussed on probiotics taken in the form of supplements
(because supplements are more profitable for manufacturers, and easier for
researchers to measure). While we don’t know with certainty if fermented foods
that are rich in these same probiotics would generate the same results, it
stands to reason that eating fermented foods that are rich in probiotics can
convey many of (if not more of) the same benefits.
1. They help rebuild gut flora with good bacteria
Fermented foods are rich in a diverse array of probiotic
microbes that can be friendly to your gut. They’re known for
helping keep you regular, reducing diarrhea, and improving digestion. The
probiotics in fermented foods work to promote a healthy microbial diversity in
your gut microbiome,
which reduces gas and bloating.
A 2012 meta-analysis published
in PLoS One looked at which digestive conditions saw the most
benefit from probiotics, such as those found in fermented foods. The
researchers concluded that infectious diarrhea, irritable bowel syndrome, Helicobacter
pylori, Clostridium difficile, and antibiotic-associated
diarrhea were among the conditions positively impacted by probiotics.
Other research concurs that probiotics can be beneficial for
people suffering from inflammatory bowel diseases like Crohn’s disease,
as well as irritable bowel syndrome.
2. The probiotics in fermented foods can be beneficial to
your immune system
Next time you’re sick, you might want to consider eating
A 2014 meta-analysis published in the British
Journal of Nutrition looked at twenty randomized controlled trials on
the impact of Lactobacillus and Bifidobacterium (probiotic strains often found
in fermented foods like yogurt, sauerkraut, and kimchi) on the duration of
acute respiratory illnesses. The researchers concluded that
probiotics can reduce the length of time that otherwise healthy kids and adults
In 2008, researchers published a remarkable study in
the Journal of Clinical Gastroenterology. Several hundred healthy,
adult volunteers were randomly divided into two groups. One of the groups took
a probiotic/prebiotic blend daily for 90 days, during the height of flu season.
The other group took a placebo for the same period of time. What do you think
were the results? Those taking the probiotic/prebiotic supplement had a 75%
reduced incidence of flu and flu-like respiratory illnesses, and a nearly 40%
reduced incidence of colds.
In addition to probiotics, some fermented foods are abundant
sources of essential vitamins and minerals that are good for your immunity. For
instance kimchi is
rich in vitamin A, vitamin C, and vitamin K, as well as in calcium, iron, and
phosphorous, and selenium.
3. They may support your mental health
Leading-edge research is
finding that your nervous system and your intestinal system are in constant
communication. When one feels poor, so does the other. A healthy microbial
balance, such as can be supported by fermented foods, can be good for your gut
and, therefore, your brain.
In fact, a growing body of research indicates that
fermented foods may be protective against depression, anxiety, and other mental
As we know, fermented foods are high in probiotics. How do
probiotics affect your mental health? A 2016 review published
in the Journal of Neurogastroenterology and Motility looked at
38 human and animal studies, finding that probiotics — mostly Bifidobacterium
longum, Bifidobacterium breve, Bifidobacterium infantis, Lactobacillus
helveticus, and Lactobacillus rhamnosus — can be
beneficial for people with depression, anxiety, obsessive-compulsive disorder,
autism spectrum disorder, and even memory impairments.
4. They may be good for your waistline
Abundant research affirms the
health benefits of kimchi. It can be good for your immune system, for fighting
aging and cancer, and perhaps most prominently of all, for supporting healthy
weight loss. But one question persists. Kimchi is made of fermented vegetables
and spices, which are known to be health-promoting even when they aren’t
fermented. So are the benefits of fermented kimchi just a result of healthy raw
ingredients, or does the fermentation contribute something special?
Seeking to answer this question, in 2011 researchers published a study
in Nutrition Research. In the study, 22 overweight and obese
adults were randomly assigned to two 4-week diet phases, during which they
added either fresh or fermented kimchi to their diet. Measurements of body
weight, body mass index, and body fat were taken. The findings showed that
eating fermented kimchi had more positive impacts on health than fresh
(unfermented) kimchi. Fermented kimchi was associated with a significant
decrease in waist to hip ratio, and body fat percentage.
In another 2014 study in the British
Journal of Nutrition, women who took Lactobacillus rhamnosus (a
probiotic found in many fermented foods) for three months, in addition to being
on a weight loss diet, lost 50% more weight than those who followed the same
diet program but didn’t take the probiotic.
Fermented foods may also reduce inflammation,
which is an immune response that can trigger weight gain.
5. They may promote heart health
A 2011 study found that adults
who consumed fermented kimchi saw a significant reduction in their fasting
blood glucose, blood pressure, and total cholesterol levels — all important
biomarkers for heart health. And researchers at the Pusan National University
in Korea found that
fermented kimchi could lower LDL cholesterol levels and reduce the risk of
strokes and heart attacks.
How to Ferment Foods
If you’re interested in fermenting your own foods at home,
it’s a surprisingly straightforward (and inexpensive) process. Two of the
easiest and most satisfying options are homemade sauerkraut and kimchi.
Sauerkraut and kimchi are very similar, as both are essentially lacto-fermented
cabbage. Sauerkraut uses white cabbage (the most common type of cabbage in
North America and Europe) and is often spiced with caraway seeds. Kimchi starts
with chinese cabbage and it is usually spiced with chillies or chili paste and
garlic. While both sauerkraut and kimchi can have a variety of seasonings and
spices added, kimchi is typically spicier.
Here are the basic steps for
fermenting your own sauerkraut (or kimchi) at home.
- Sterilize all of your equipment, including your jar
(mason jars with screw top lids work well). If you sterilize equipment
with boiling water or in a dishwasher, make sure to let everything cool to
room temperature before you start adding your ingredients.
- Finely grate your cabbage (or chinese cabbage) and
add it to a large mixing bowl, along with canning and pickling salt (about
1 ½ tsp salt for every 8 cups of grated cabbage is a good ratio). With
clean hands, massage these together while the cabbage softens and shrinks.
- Add other ingredients (e.g., shredded beets and
carrots, seasonings like garlic, chilies, or ginger) to the cabbage
mixture and use your hands again to massage them together.
- Place your sauerkraut mixture into the sterilized
mason jar, pressing it down firmly. Liquid should rise up to the top, but
if it doesn’t cover the top, add some filtered water.
- Screw on your lid, leaving 1-2 inches of room between
the lid and the top of your sauerkraut so that it has room to expand as it
- Keep your sauerkraut at room temperature, around
65°F, for best results. Fermentation can take anywhere from 24 hours to 2
- Once per day, open the lid to your jar to release any
built up carbon dioxide. Use a clean spoon to press the sauerkraut back
underneath the liquid if it has risen.
- When your sauerkraut or kimchi has reached your
desired level of fermentation and flavor, it can be kept in the fridge for
To make your own fermented yogurt at
home, follow these steps:
Note: This works best if you use a yogurt maker (or make it
in the oven with the oven light on) and a yogurt starter culture.
- Sterilize all of your equipment, either by using
boiling water or running them through the dishwasher. Let everything cool
to room temperature before using.
- Use a thermometer and add full-fat “milk” (can be
soy, coconut, or other varieties) to a large pot and heat it to 180°F.
Stir gently so that it doesn’t start creating a film or burning on the
bottom. Note that you can also add a thickener during
this step, like agar agar powder, if desired.
- Remove the milk from the heat source and let it cool
- Add the starter culture to your warm milk and whisk
it until dissolved.
- Pour your yogurt mixture into yogurt making
containers. Leave it here for 5-10 hours at 110-115°F. Many ovens reach
and stay at this temperature with the oven door closed and the oven light
left on. Some people also find that a heating pad, left on inside a
sleeping bag, creates the desired temperature. The longer you leave your
yogurt fermenting, the thicker and more tart tasting it will become.
- When the desired thickness is reached, transfer your
yogurt to the refrigerator for 2-3 hours until it’s cold.
- Store your yogurt in the fridge for up to 2 weeks.
Note: If you have a yogurt
maker, the process may be simpler, and you should follow the instructions
that come with it.
Safety Concerns With Fermented Foods
Although fermented foods offer many health benefits, it’s
important to be aware of potential safety concerns when making or buying
Overall, there’s less risk of contamination in fermented
foods as compared to canned foods. However, bad bacteria and mold can grow if
the fermentation isn’t done properly.
For instance, exposing your ferment to too much air or an
improper growth environment can lead to yeast overgrowth or even to rotting.
Sometimes this occurs if you start with an unclean container, don’t use
an adequate amount of salt, or ferment at the wrong temperature.
To avoid these
mistakes, it’s important to keep your ferment at the right temperature for
optimal growth, and to add the right amount of salt or brine. If using salt,
“canning and pickling salt” is usually what’s recommended. It is coarser than
table salt. An ideal temperature for most ferments (other than yogurt and
kefir) is between 68°F and 75°F, above which spoilage is a higher risk.
Foodborne illnesses from consuming fermented foods is not
common, though, and when it does occur, it mainly happens after consuming
animal-based fermented foods.
Side Effects of Eating Fermented Foods
If you’re new to eating fermented foods, or you eat them
somewhat sporadically, there are several potential side effects you may
Some of the most common side
One reason you may be hit with side effects is if you
introduce fermented foods too quickly. Some people are sensitive to fermented
foods, and need a slow initial introduction. If this is the case for you, you
might want to start with a tablespoon of sauerkraut, instead of downing ½ cup
of it. Work your way up slowly and your body – and the trillions of
microorganisms in your gut – will likely adapt.
Another reason could be that you’re eating them alongside
protein-rich foods. Protein takes longer to digest, so when it’s eaten at the
same time as a gut-friendly fermented food, this can in some cases lead to gas
It’s also possible that you could have a food or histamine
intolerance, or that you’re sensitive to FODMAPs (if you’re studying to appear
on Jeopardy, that stands for Fermentable Oligo-, Di-, Mono-saccharides And
Polyols) — short-chain carbohydrates like fructose and lactose that are often
found in fermented foods. Kombucha, kimchi, and sauerkraut are high in FODMAPs,
and may be difficult for someone with a sensitivity to tolerate.
Be Mindful of the Salt in Fermented Foods
Keep in mind, too, that many fermented foods, like kimchi,
miso, and sauerkraut, are high in sodium. For example, 4 Tablespoons of sauerkraut contain
nearly 400 mg of sodium, or almost 20% of your Daily Value, and just 1
Tablespoon of miso has
775 mg of sodium. Regularly eating a lot of salty fermented foods could be
problematic especially for people with high blood pressure. Salty foods
can also dehydrate you pretty quickly, and cause your body to excrete
To reap the benefits without overdoing the sodium, you can
use things like sauerkraut and kimchi as a salt source for flavoring many
meals. For instance, they can be added to wraps and cold pasta dishes, or to
top warm dishes like burritos and casseroles. Just don’t cook them so that the
live probiotics won’t be killed off by
Fermented Foods Recipes
f you’re interested in giving some homemade fermented foods
a shot, here are some great recipes to try.
Sauerkraut by Wellness Mama – This is a simple, countertop recipe that
only uses 3 ingredients and takes 30 minutes to prepare (and then 2-5 weeks to
Simple Fermented Carrot Sticks Recipes by Holly at MakeSauerkraut! –
These tasty recipes are a great way to give fermenting a try at home. With five
flavor options, as well as instructions for creating a 2% brine solution,
you’ll be confidently fermenting in no time.
Cashew Yogurt by Simple Vegan Blog – This recipe proves that you don’t
need high-sugar, dairy-based yogurt to enjoy the probiotic benefits of this
fermented food. Using non-dairy ingredients and probiotic supplements, this
easy recipe is healthy and delicious.
Add Fermented Foods to Your Diet
The best way to get the most benefit from eating fermented
foods is to incorporate a variety of them into your diet. You may find that you
like some more than others, or that certain ones have specific uses that you
enjoy. Because fermentation has been around for such a long time, different
fermented foods can give a “signature” cultural flavor to an otherwise neutral
dish. Even small amounts can have an outsized influence on your taste buds:
Just a few of the Fermented Firecracker Carrot Sticks from MakeSauerkraut!,
featuring jalapeno peppers and oregano, will give your salad or wrap a
distinctive “South of the Border” vibe. A couple tablespoons of miso can turn
your vegetable noodle soup from Eastern European to Asian.
If you’re feeling adventurous, you can even make your own
fermented foods at home, starting with the instructions and recipes in this
article. For extra drama, wait for thunderstorms and find a kitchen helper to
say “Yes, Dr. Frankenstein” and “I do believe this just might work” at critical
junctures in the process.
Whether you buy ready-made or ferment your own, the
potential benefits to your health are worth giving some new fermented foods a
try. Not only may you find them delicious, but about 50 trillion of your little
buddies will consider them a wonderful treat. And it’s always a good idea to
trust your gut!