Health Benefits of Natto

Medically reviewed by Simone Harounian, MS

Natto is a fermented soybean dish native to Japan. As the soybeans ferment, they form polyglutamic acid, which gives natto a distinct sticky consistency. Some say it’s an acquired taste, but it’s also a beloved food by many.

In Japan, natto is often enjoyed for breakfast served over rice and mixed with raw egg, soy sauce, and green onions. Even if you don’t live in Japan, you can find natto at most Asian grocery stores. It’s often sold in individual packages that you can microwave to warm up, although you can also find it sold in glass jars.

Part of the reason natto is more readily available in the United States now is because of its health benefits. It’s a nutrient-dense food rich in vitamins, minerals, plant protein, polyunsaturated fat, and fiber. Studies show it may benefit heart health, gut health, and fight inflammation.

Supports Heart Health

There are many ways natto supports heart health. For one, the fiber and polyunsaturated fat in natto can help reduce LDL cholesterol levels—the “bad” kind of cholesterol. Having high cholesterol is a risk factor for heart disease, so being mindful of cholesterol levels is important for your overall heart health.

Related: The 13 Best Foods to Lower Cholesterol

Research has found that natto consumption is linked with a reduced risk for heart disease. This may be in part due to nattokinase—an enzyme produced through the fermentation of natto. Nattokinase has been shown to help lower blood pressure, reduce blood lipid levels, prevent plaque formation in the arteries, and act as a blood thinner. These are all qualities that support cardiovascular health.

May Promote Healthy Blood Pressure

High blood pressure increases the risk of heart attack, stroke, heart failure, and more if left uncontrolled over time. If you have high blood pressure, natto may be a food worth adding to your diet.

One study that included 79 North American participants with hypertension found that consuming nattokinase improved the participants’ blood pressure. However, this was just one study and it had a relatively small sample size, so more robust studies are needed to confirm natto’s benefits on blood pressure.

Natto also contains several nutrients important for blood pressure management. These include calcium, potassium, magnesium, fiber, and protein—all nutrients encouraged in the Dietary Approaches to Stop Hypertension (DASH) eating plan. Plus, it’s a low-sodium food—another important nutrition consideration for blood pressure management.

Supports Gut Health

Eating natto can help support gastrointestinal health as it's a high-fiber, fermented food.

Fiber is a key nutrient for gut health. Fiber helps promote gut motility, a healthy gut microbiome, and the health of your colon.

Fermented foods have been shown to have a positive impact on the health of the gut microbiome, or the diverse spread of bacteria that live in the gastrointestinal tract. Recent research has found evidence that having a healthy gut microbiome can improve your mental and physical health, and help prevent or treat many metabolic disorders.

The bacteria Bacillus subtilis used to ferment natto acts as a probiotic—live microorganisms that can help support a healthy microbiome. Research has found that Bacillus strains may exert beneficial effects on the gut microbiome and help counter inflammation in the gut. However, many of these studies have been done on animals or in test tubes, so more studies on humans are needed to further explore these benefits.

Related: 5 Best Types of Food To Eat For a Healthy Gut

Reduces Inflammation

Natto may also play a role in reducing inflammation. Studies have found that soy isoflavones, which are phytoestrogens found naturally in soybeans, may help reduce inflammation, particularly when it's related to menopause.

Studies have also found that soy protein supplementation has anti-inflammatory effects by reducing circulating levels of inflammatory cytokines.

While these studies didn’t evaluate natto specifically, the nutrients studied are present in natto. More natto-specific research is needed to confirm these benefits.

Also, lunasin—a peptide found naturally in soybeans—has been shown to inhibit pro-inflammatory cytokines like TNF-α and IL-6. However, most of the studies on lunasin’s benefits on inflammation have been conducted in vitro or in animal models, so human studies are needed to verify these potential benefits.

Related: 13 Foods That Fight Inflammation

Nutrition of Natto

Since natto is made from soybeans—a legume—it’s an excellent source of plant-based protein and fiber, and it’s also rich in vitamins and minerals. One cup of natto contains:

• Calories: 369

• Fat: 19.2 grams (g)

• Saturated Fat: 2.8 g, or 14% of the daily value (DV)

• Unsaturated Fat: 16.4 g

• Sodium: 12 milligrams (mg)

• Carbohydrates: 22 g

• Fiber: 9.5 g, or 34% of the DV

• Protein: 34 g

• Calcium: 380 mg, or 29% of the DV

• Magnesium: 200 mg, or 48% of the DV

• Potassium: 1280 mg, or 27% of the DV

• Zinc: 5.3 mg, or 44% of the DV

Natto is an incredibly nutrient-dense food. Like other legumes, it’s rich in plant protein and fiber, which supports gut and metabolic health while reducing inflammation in the body.

It’s also full of vitamins and minerals. Besides having the ones listed above, natto is an excellent source of selenium, vitamin C, thiamin, riboflavin, choline, and vitamin K.

Although it's high in fat, most of the fat in natto is polyunsaturated. Polyunsaturated fat can reduce LDL cholesterol—the “bad” kind of cholesterol—which could reduce your risk for heart disease and stroke.

Risks of Natto

The most common risks or side effects of natto are digestive symptoms like diarrhea or constipation. Since natto is a high-fiber food, eating too much of it at once, especially if you don’t typically eat high amounts of fiber, could cause gas, bloating, and diarrhea.

Also, natto is made of soy, so people with soy allergies should not consume it. Soy is one of the eight most serious allergens, according to the CDC. Some signs of an allergic reaction to soy can include:

• Shortness of breath

• Wheezing

• Swelling of the tongue or lips

• Tightness in the throat

• Weak pulse

• Hives
  

• Dizziness

• Vomiting

Plus, soy products can interact with certain medications. This is typically the case with soy-based supplements that have higher doses of soy isoflavones, but it’s still best to consult with your healthcare provider before eating natto if you’re taking one of the following medications:

• Warfarin (Coumadin)

• Tamoxifen (Soltamox)

• Levodopa (Rytary)

• Ciprofloxacin (Cetraxal)

Soy isoflavones present in natto may interfere with your body’s ability to break down and absorb these drugs.

Soy is considered to be a safe food. There is some information questioning whether soy is safe for people who have had or are at risk for breast cancer due to soy's phytoestrogen content (substances that mimic estrogen). Current research indicates soy foods are safe for these groups.

However, soy in more concentrated amounts, such as in soy isoflavone supplements, may not be safe for these groups, or for people who are pregnant or breastfeeding. Soy isoflavone supplements will have much higher doses of phytoestrogens.

Tips for Consuming Natto

Natto may be an acquired taste if you’re not used to having it, but there are many fun ways to incorporate it into your diet. In Japan, where natto is from, it’s often eaten with rice and a raw egg.

Here are a few other tips for storing and eating natto:

• Store it in an airtight container to keep it fresh

• Heat it up before enjoying it. The microwave works great for this

• Enjoy natto on its own

• Make Natto Gohan—a Japanese breakfast dish of rice topped with natto, soy sauce, Japanese mustard, and green onion

• Experiment with toppings like avocado, kimchi, ginger, seaweed, egg, and miso

• Add it to salad or udon soup

• Mix it into fried rice or pasta

A Quick Review

Natto is a fermented soybean dish packed with fiber, micronutrients, and plant protein to support heart and digestive health. It may also help fight inflammation. Natto is native to Japan, but can be found in many Asian grocery stores. The food has a distinct flavor and sticky texture.

Since natto is made of soy, people who are allergic to soy should not eat this food. If you experience swelling of the tongue and lips, shortness of breath, or dizziness while eating natto, you may be having an allergic reaction and should seek emergency medical care.

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