Fermentation is a process in which bacteria and yeast break down sugars.

Not only does it enhance food preservation, but eating fermented foods can also boost the number of beneficial bacteria, or probiotics, in your gut.

Probiotics are associated with a variety of health benefits, including improved digestion, better immunity, and even increased weight loss (1, 2, 3).

Here are 8 fermented foods and drinks that have been shown to improve health and digestion.

homemade kombucha in jar, glass, and bottleShare on Pinterest
Melanie Riccardi/Stocksy United

Kefir is a type of cultured dairy product.

It’s made by adding kefir grains — which are a combination of yeast and bacteria — to milk. This results in a thick, tangy beverage with a taste that’s often compared to yogurt.

Studies reveal that kefir has numerous health benefits, from digestion to inflammation to bone health.

In a small, older study, kefir was shown to improve lactose digestion in 15 people with lactose intolerance. People with this condition can’t digest the sugars in dairy products, leading to symptoms like cramps, bloating, and diarrhea (4).

Kefir also contains less lactose than milk. When kefir grains and milk are combined to make kefir, the bacteria in the grains help ferment and break down the lactose in the milk (5).

Another older study found that consuming 6.7 ounces (200 mL) of kefir daily for 6 weeks decreased markers of inflammation, which is known to contribute to chronic conditions like heart disease and cancer (6, 7).

This tangy drink may also boost bone health.

In a 6-month study including 40 people with osteoporosis — a condition characterized by weak, porous bones — those who drank kefir had improved bone mineral density compared with the control group (8).

You can enjoy kefir on its own or blend it into smoothies and drinks.

SUMMARY

Kefir is a fermented dairy product that may improve lactose digestion, decrease inflammation, and boost bone health.

Tempeh is made from fermented soybeans that have been pressed into a compact cake.

This high protein meat substitute is firm but chewy and can be baked, steamed, or sautéed before being added to dishes.

In addition to its impressive probiotic content, tempeh is rich in many nutrients that may improve your health (9).

For example, soy protein has been shown to help reduce certain risk factors for heart disease.

One review of more than 40 studies noted that eating 25 grams (0.88 ounces) of soy protein every day for 6 weeks led to a 3.2% decrease in LDL (bad) cholesterol and a 2.8% decrease in total cholesterol (10).

Additionally, an older test-tube study found that certain plant compounds in tempeh may act as antioxidants. Antioxidants reduce the buildup of free radicals, which are harmful compounds that can contribute to chronic disease (11).

Tempeh is perfect for vegetarians and omnivores alike. It’s particularly suited to dishes like sandwiches and stir-fries.

SUMMARY

Tempeh is made from fermented soybeans. It’s high in probiotics, may boost heart health, and may even offer antioxidants.

Natto is a staple probiotic food in traditional Japanese cuisine.

Like tempeh, it’s made from fermented soybeans. It has a very strong flavor and slimy texture.

It contains a good amount of fiber, providing 5.4 grams per 3.5-ounce (100-gram) serving (12).

Fiber may help support digestive health. It moves through your body undigested, adding bulk to stool to help promote regularity and alleviate constipation (13).

Natto is also high in vitamin K, an important nutrient that’s involved in calcium metabolism and bone health (12).

In studies including hundreds of Japanese women, natto intake was associated with reduced bone loss in those who were postmenopausal (14, 15).

The fermentation of natto also produces an enzyme called nattokinase. In a study including 12 young Japanese men, supplementing with nattokinase just one time helped prevent and dissolve blood clots (16).

Other studies also found that taking this enzyme helped reduce diastolic and systolic blood pressure.

In an 8-week Japanese study, diastolic and systolic blood pressure dropped by 2.84 and 5.55 mmHg, respectively, while they dropped by 3 and 4 mmHg, respectively, in an 8-week North American study (17, 18).

Natto is often paired with rice and served as part of a digestion-boosting breakfast.

SUMMARY

Natto is a fermented soybean product. Its high fiber content may promote bowel regularity and help prevent bone loss. It also produces an enzyme that may reduce blood pressure and dissolve blood clots.

Kombucha is a fermented tea that’s fizzy, tart, and flavorful. It’s made from either green or black tea and offers these drinks’ potent health-promoting properties.

Animal studies show that drinking kombucha may help prevent liver toxicity and damage caused by exposure to harmful chemicals (19, 20, 21).

Plus, test-tube studies have found that kombucha may help induce cancer cell death and block the spread of cancer cells (22, 23).

Some animal studies have even found that kombucha helped reduce blood sugar, triglycerides, and LDL (bad) cholesterol (24, 25).

Although these results are promising, further human research is needed (26).

Thanks to its rising popularity, kombucha can be found at most major grocery stores. You can also make it at home, though it should be prepared carefully to prevent contamination or overfermentation.

SUMMARY

Kombucha is a fermented tea. Although more research is needed, animal and test-tube studies have found that it could help protect the liver, decrease blood sugar, and reduce levels of cholesterol and triglycerides.

Miso is a common seasoning in Japanese cuisine. It’s made by fermenting soybeans with salt and koji, a type of fungus.

It’s most often found in miso soup, a flavorful dish made of miso paste and stock. Miso soup is traditionally served for breakfast.

Several studies have found health benefits tied to miso.

An older study in 21,852 Japanese women linked eating miso soup to a lower risk of breast cancer (27).

Another older study including over 40,000 people associated a higher intake of miso soup with a lower risk of stroke in Japanese women (28).

Miso may also help lower blood pressure and protect heart health. In fact, a study in rats found that long-term miso soup intake helped normalize blood pressure levels (29).

Plus, a study including middle-aged and older Japanese adults found that frequent miso soup intake may lead to a lower heart rate. This study also concluded that miso soup didn’t elevate blood pressure, despite its saltiness (30).

However, other Japanese studies have linked miso soup intake — and its large amounts of salt — to a higher risk of stomach cancer.

In one study, eating 3–4 cups of miso soup per day raised the risk of stomach cancer, while in another study, men who ate 1–5 cups per day saw their stomach cancer risk increase (31, 32).

Overall, more studies are needed to evaluate miso’s health effects.

Besides stirring miso into soup, you can try using it to:

  • glaze cooked vegetables
  • spice up salad dressings
  • marinate meat
SUMMARY

Miso is a seasoning made from fermented soybeans. It’s associated with improved heart health and a reduced risk of certain cancers, though more human studies are needed.

Kimchi is a popular Korean side dish that’s usually made from fermented cabbage or other fermented veggies like radishes.

It boasts an extensive array of health benefits and may be especially effective at lowering cholesterol and reducing insulin resistance.

Insulin is responsible for transporting glucose from your blood to your tissues. When you sustain high levels of insulin for long periods, your body stops responding to it normally, resulting in high blood sugar levels and insulin resistance.

In one study, 21 people with prediabetes ate either fresh or fermented kimchi. After 8 weeks, those eating fermented kimchi had decreased insulin resistance, blood pressure, and body weight (33).

In another study, people were given a diet with either a high or low amount of kimchi for 7 days. A higher intake of kimchi — 7.4 ounces (210 grams) daily compared with 0.5 ounces (15 grams) — led to greater decreases in blood sugar, cholesterol, and LDL (bad) cholesterol (34).

Kimchi is easy to make and can be added to everything from noodle bowls to sandwiches.

SUMMARY

Kimchi is made from fermented vegetables like cabbage or radishes. Studies have found that it may help reduce insulin resistance and cholesterol levels.

Sauerkraut is a popular condiment consisting of shredded cabbage that has been fermented by lactic acid bacteria. It’s low in calories but contains plenty of fiber and vitamins C and K (35).

Like other foods made with leafy green vegetables, it also contains a good amount of lutein and zeaxanthin. These antioxidants help promote eye health and reduce your risk of eye disease (36).

The antioxidant content of sauerkraut also boasts promising effects on cancer prevention.

One test-tube study showed that treating breast cancer cells with cabbage juice decreased the activity of certain enzymes related to cancer formation. However, the current evidence is limited, and human research is needed (37).

You can use sauerkraut in countless dishes, from casserole to soup to sandwiches.

To get the most health benefits, be sure to choose unpasteurized sauerkraut since pasteurization kills beneficial bacteria.

SUMMARY

Sauerkraut is made from fermented shredded cabbage. It’s high in antioxidants that are important for eye health and easy to add to many dishes.

Yogurt is produced from milk that has been fermented, most commonly with lactic acid bacteria.

It’s high in many important nutrients, including calcium, potassium, phosphorus, riboflavin, and vitamin B12 (38).

Yogurt has also been associated with a wide variety of health benefits.

One review of 14 studies showed that fermented milk products, including probiotic yogurt, may help reduce blood pressure — especially in those with high blood pressure (39).

Another study linked a higher intake of yogurt to improvements in bone mineral density and physical function in older adults (40).

This creamy dairy product may also help prevent weight gain. One review associated eating yogurt with a lower body weight, less body fat, and a smaller waist circumference (41).

Remember that not all yogurts contain probiotics, as these beneficial bacteria are often killed during processing. Look for yogurts that contain live cultures to make sure you’re getting your dose of probiotics. Additionally, opt for products with minimal sugar.

SUMMARY

Probiotic yogurt is made from fermented milk. It’s high in nutrients and may help reduce body weight, lower blood pressure, and improve bone health.

What foods are considered fermented?

The term “fermented foods” refers to any foods that have undergone the process of fermentation, which is the chemical breakdown of sugar by yeast and bacteria (9).

This includes all of the foods listed above, such as:

  • kefir
  • tempeh
  • natto
  • kombucha
  • miso
  • kimchi
  • sauerkraut
  • probiotic yogurt

Can fermented food be toxic?

Although most fermented foods are generally considered safe, some varieties — including fermented milk products like kefir — are more susceptible to contamination with toxins and bacteria (42).

Fortunately, practicing proper food safety can help minimize the risk of contamination and spoilage. Soaking or washing fermented foods, as well as heating, freezing, or thawing foods, may also be beneficial (42).

How often should you eat fermented foods?

While there are currently no official guidelines regarding how often you should eat fermented foods, adding a few servings to your daily diet may be beneficial (43).

For the best results, start by eating one or two servings per day, then slowly work your way up.

Getting probiotics through whole foods is a simple way to take advantage of fermented foods’ health benefits while reducing your risk of side effects associated with probiotic use, such as digestive issues (44).

Fermentation may help increase both the shelf life and health benefits of many foods.

The probiotics in fermented foods have been associated with improvements in digestion, immunity, weight loss, and more (1, 2, 3).

In addition to containing these beneficial probiotics, fermented foods aid many other aspects of health and are an excellent addition to your diet.