Slimy Yet Satisfying: The Health Benefits of Natto

by Evan DeMarco

Where do you get your probiotics? Supplements, sauerkraut, kombucha, pickles, yogurt and kimchi are all popular fermented foods that can help balance your gut microbiome. But if you haven’t tried natto, you’re missing out on one of the most unique fermented foods around.

Natto is a Japanese specialty. These fermented soybeans end up with a slimy, sticky and stringy texture and a distinctive, pungent smell. While that’s perhaps not the most appetizing description, natto is packed with probiotics and nutrients.

Is natto your next favorite source of probiotics, or will you skip this fermented food? Read on to learn more about the dish and why it’s so good for you.

How natto is made and served

Natto is made from fermented soybeans. Traditionally, cooks wrapped boiled soybeans in rice straw, which provided the bacteria Bacillus subtilis. This allowed the bacteria to ferment the sugars in the soybeans, which eventually produced natto—slime, strings and all.

In the early 20th century, scientists were able to isolate B. subtilis. This allowed cooks to make natto without having to use rice straw. Today, natto is made in Styrofoam boxes: cooks simply add the boiled soybeans and the isolated bacteria to begin fermentation.

Many people describe natto as having a strong, earthy or nutty flavor and a distinct strong smell. The flavor and texture may vary, depending on the fermentation process. Natto is typically served over cooked rice, along with chives, seasonings, soy sauce and/or mustard. This makes it a particularly filling meal—and, as you’ll see, a particularly nutritious one, too.

Nutritional facts

According to Healthline, a 3.5 ounce serving of natto contains the following nutrients:

  • Calories: 212
  • Fat: 11 grams
  • Carbs: 14 grams
  • Fiber: 5 grams
  • Protein: 18 grams
  • Manganese: 76% of the RDI
  • Iron: 48% of the RDI
  • Copper: 33% of the RDI
  • Vitamin K1: 29% of the RDI
  • Magnesium: 29% of the RDI
  • Calcium: 22% of the RDI
  • Vitamin C: 22% of the RDI
  • Potassium: 21% of the RDI
  • Zinc: 20% of the RDI
  • Selenium: 13% of the RDI

Natto also contains vitamin B6, folate, pantothenic acid and antioxidants. The fermentation process produces probiotics, those beneficial bacteria that help regulate your gut microbiome. They also help you digest your food better, which leads to better nutrient absorption. Non-fermented soybeans are healthy, but natto’s nutritional content is superior.

Of course, if you eat natto, the rice and flavorings will add extra calories and nutrients. Don’t forget to take those into account when you prepare your meal.

Natto’s biggest benefits

Natto packs a nutritional wallop. Here’s how it can boost your health:

  • Stronger bones: A single serving of natto offers over a fifth of your calcium RDI, which helps build strong bones. It’s also a source of vitamin K2, which promotes bone-building proteins. K2 has been shown to slow down age-related bone density loss, and can even reduce your risk of bone fractures.
  • Heart health: Fiber and probiotics—both present in natto—reduces cholesterol levels. But that’s not all natto offers in service of heart health. Nattokinase is an enzyme that can help dissolve blood clots. (It’s concentrated in the stringy bits.) Natto also helps control your blood pressure and prevents calcium from building up in your arteries.
  • Immune boost: Probiotics create healthy gut flora, which prevents harmful bacteria and pathogens from making you sick. They can also reduce your risk of infection, and help you recover faster from illnesses.
  • Weight loss: Because probiotics are so great for your gut microbiome, and because natto is packed with fiber, it can help you lose weight. Fiber helps you feel fuller longer, reducing cravings for other food.
  • Brain health: Probiotics in general have been linked to improved memory, reduced stress, and lowered symptoms of OCD, autism, depression and anxiety.
  • Reduced cancer risk: Natto contains vitamin K2 and soy isoflavones, which have been linked to lower risk of certain cancers like breast, digestive, liver and prostate cancer.

Can you stomach the slime?

If natto doesn’t sound appealing to you, we can’t blame you—slimy, sticky and stringy sounds like something you’d find on a horror movie set, not a healthy meal. However, some people find the flavor and texture downright addictive.

You don’t have to miss out on all of natto’s health benefits if you eschew the dish, however. Nattokinase supplements are available at health food stores near you. Whether you opt for a slimy yet satisfying traditional dish, or get your nattokinase in pill form, the health benefits are too good to ignore.

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