Natto vs. Tempeh: Comparing Two Soy Superstars

If you follow a vegan diet or are looking for ways to reduce your meat consumption, you’ve probably come across natto and tempeh as commonly mentioned sources of plant-based protein. While these foods have been popular in certain areas of Asia for hundreds of years, the Western world is just beginning to catch on to their impressive nutritional benefits and versatility in cooking.

At first glance, they seem to be very similar as both are made from fermented soy. While they do have some culinary and nutritional similarities, we see some interesting differences when we compare natto vs. tempeh in more detail.

Let’s discuss how these unique soy-based foods differ in terms of their nutrition profile, culinary uses, and health benefits so that you can find the best way to include one or both of them in your diet.

Natto and nori on wood table

Natto vs. tempeh – a quick comparison

Natto and tempeh are both highly nutritious foods made from fermented soybeans. Natto is a traditional Japanese food with a sticky, slimy texture and strong odor, while tempeh originates from Indonesia and has a firmer texture and more neutral flavor. 

The production process for each is similar, involving soaking the soybeans, cooking them, inoculating them with bacteria (Bacillus subtilis for natto, Rhizopus for tempeh), and allowing the bacteria to ferment.

Both are high in anti-inflammatory isoflavones, protein, and dietary fiber, while natto is higher in vitamin K2 and contains the blood-thinning enzyme nattokinase. Tempeh is higher in folate and choline and contains a small amount of vitamin B12, although it isn’t considered a reliable source of the latter.

Taste, aroma, and appearance

Natto and tempeh are both fermented foods made from soybeans, but they differ significantly in terms of their flavor, aroma, and appearance.

Natto has a characteristically strong, unpleasant smell resulting from the Bacillus subtilis strain of bacteria that it’s cultured with. It also has a wet, gooey, slimy texture with the soybeans loosely held together by a stringy web of bacteria. 

Tempeh is much firmer in texture and is sold as compact blocks in which whole soybeans are tightly held together. It may have dark streaks running through it, which shouldn’t cause concern – this is natural discoloration from the fermentation process.

Depending on the natto type, it can either be a brown or light tan color. The outside of a block of tempeh is often a whiteish color resulting from the visible bacteria on it, while the inside is a light gray or beige color.

Culinary uses

Since natto and tempeh originated from different regions of Asia, they have traditionally been used in different ways.

In Japan, natto is used to add flavor1 to meat, fish, and vegetables and is often served with steamed rice, soy sauce, onion, and mustard seaweed. In Indonesia, tempeh is eaten deep-fried as a snack with various seasonings and sauces to add flavor. It’s also simmered and served in stews.

In Western countries, tempeh is much more popular and available than natto and is used in many plant-based dishes in place of ground beef or pork or as a substitute for tofu. Some of my favorite ways to prepare tempeh are as tempeh “bacon”, in tacos, and as a “meat” sauce for vegan lasagna or spaghetti. 

Natto vs. tempeh: nutrition profile

Natto and tempeh are both highly nutrient-dense foods and excellent sources of plant-based protein, iron, dietary fiber, and vitamin K2. They’re both naturally gluten-free, although there are some caveats — natto is often sold along with sauces that contain gluten, and tempeh may not be gluten-free if pre-seasoned or processed with certain grains. 

Table comparing the nutrition profile of natto vs tempeh

Per cup, natto is noticeably higher in calories, carbs, calcium, selenium, iron (almost 100% of the recommended daily value), and potassium, while tempeh is a better source of folate and choline. Tempeh also contains a small amount of vitamin B12 produced through fermentation, although amounts can vary widely. Because of this, vegans shouldn’t count on tempeh as a reliable source of vitamin B12. 

Tempeh may also be higher in choline, although the USDA’s data on choline content2 is limited to what we know about the content of choline in raw soybeans, not tempeh specifically.

Health benefits & concerns

When it comes to soy (even in fermented form), misinformation and myths about its effects on our health are everywhere. Here I’ll discuss the evidence-based health benefits of natto and tempeh and whether they pose any risks to humans.

Health benefits

The health benefits of fermented soy foods are pretty incredible! Let’s discuss them in more detail below.

Soy phytoestrogens

One of the unique benefits of soy-based foods like natto and tempeh is their content of anti-inflammatory phytoestrogens, also called “plant estrogens” or isoflavones. These natural compounds are similar in appearance to the estrogen produced by mammals, including humans, but they don’t always act the same way as mammalian estrogen. 

Phytoestrogens can either act similarly to estrogen or block estrogenic activity, depending on the area of the body. This may be one reason why phytoestrogens are associated with a reduced risk of breast cancer in pre- and post-menopausal women, according to a 2022 systematic review3.

Improved nutrient absorption

Natto and tempeh are both fermented foods. During fermentation, “anti-nutrients” such as phytic acid and lectins are deactivated, making some vitamins, minerals, and isoflavones in natto and tempeh more easily absorbed by the body. Another way of saying this is that fermentation helps improve nutrient bioavailability4

Don’t be overly concerned about anti-nutrients in unfermented soy foods like soy curls, edamame, or most tofu, however – the cooking process also deactivates5 compounds like lectins, trypsin inhibitors, and phytic acid. So unless you’re eating raw soybeans (unlikely), there isn’t much to worry about.

Calcium and vitamin K2 for bone health

When consumed regularly, natto and tempeh can both support strong bones, although in slightly different ways.

Both are good plant-based sources of calcium, with natto being an even better source with almost 400 milligrams per cup (31% of the daily value). Calcium is required for building and maintaining bones and provides them with structure and strength. 

The incredible calcium content of natto and tempeh makes them particularly good choices for vegans since plant-based foods that contain over 100 milligrams of calcium in a serving are rare.

Also required for healthy bones is vitamin K. There are two types of vitamin K: K1 and K2. Vitamin K2 is less abundant in plant-based foods but is produced by microbial fermentation in our intestines6 and during the production of natto and tempeh. 

Vitamin K27 may be particularly important in preventing bone fractures8 and improving how well the body uses calcium and vitamin D to improve bone quality, although more research is needed for us to know how significant a role it plays.

Apart from bone health, vitamin K2 appears to help prevent heart disease and improve insulin sensitivity and blood sugar control9 in type 2 diabetes. There isn’t much evidence to suggest that vegans are deficient in vitamin K2 or need supplements, but in light of its promising benefits and the scarcity of vitamin K2-rich plant-based foods, I consider natto and tempeh to be valuable foods for vegans.

Nattokinase

Natto contains a unique enzyme called nattokinase that isn’t found in tempeh or any other foods. Nattokinase is produced by the Bacillus subtilis bacteria used to produce natto and has blood-thinning and blood pressure-lowering properties9.

These effects are likely greatest when taking nattokinase as a supplement, but it may also provide some cardiovascular benefits when consumed from natto itself. Of note, nattokinase interferes with blood-thinning drugs like warfarin, so supplementation should be discussed with your physician.

Fiber content

Natto and tempeh are both excellent sources of fiber with 9 grams and 7 grams per cup, respectively. Most people don’t get enough fiber, so these foods can be helpful in meeting the daily fiber recommendation of 21-25 grams for women and 30-38 grams for men. 

Diets high in fiber are anti-inflammatory, support the health of the gut microbiome, strengthen the immune system, and can help prevent chronic diseases like heart disease, type 2 diabetes, and some types of cancer.

Tempeh skewers with peanut sauce

Health concerns and myths

Genetic engineering

While most soy grown in the US is genetically engineered to be resistant to the herbicide glyphosate, GMO soybeans are most often used as crops to feed livestock and to make soybean oil and are used less often for soy foods. 

While genetically engineered foods are tested for safety before being approved for use in the food supply, studies on the long-term health effects of these foods are lacking.

If you prefer to avoid genetically engineered soy, you can choose USDA Organic products. There are many organic tempeh and natto products available since food manufacturers know that many consumers prefer organic soy.

Impact on hormones

Contrary to popular belief, soy doesn’t have a negative impact on our hormones. Supporting this, a 2021 systematic review10 found that eating soy foods (including natto and tempeh), soy protein, and isoflavone extracts has no effect on testosterone, estrogen, or sex hormone-binding globulin levels in men.

Summary

Natto and tempeh are both fermented soy foods that are excellent sources of plant-based protein, iron, vitamin K2, calcium, and dietary fiber. Natto is also a good source of selenium and the enzyme nattokinase, while tempeh shines as a great source of folate and choline.

The most noteworthy differences between natto and tempeh are their appearance, aroma, and flavor, with natto having a strong flavor, pungent aroma, and a sticky, slimy texture. Tempeh is firmer and can be sliced, chopped, or crumbled. It also takes on the flavor of other ingredients it’s cooked with. 

Try both and see if you prefer one over the other. Overall, both natto and tempeh are nutritious additions to vegan, plant-based, and vegetarian diets!

Interested in other nutritious soy foods? Check out these helpful blog posts:

Are Soy Curls Healthy?

What Does Tofu Taste Like? (The Ultimate Flavor Guide)

Is Tempeh Gluten-Free?

Natto vs. Tempeh – FAQs

Is tempeh the same as natto?

Tempeh and natto are both fermented soy products, but they’re very different in terms of taste, texture, appearance, and culinary uses. Natto is sticky and goopy, has a pungent aroma, and is traditionally used to flavor vegetables and meat. Tempeh is firmer and can be sliced, crumbled, or chopped before it’s deep-fried, stir-fried, or sauteed. 

Is there vitamin K2 in natto and tempeh?

Natto and tempeh both contain vitamin K2, with natto containing 40 micrograms per cup compared to 32 micrograms per cup of tempeh. Both get their vitamin K2 content from the bacterial fermentation process, so in reality K2 levels will vary based on the production method used.

Does natto taste like tempeh?

Natto has a much stronger flavor than tempeh and is often used to flavor meat, fish, and vegetables. Tempeh, on the other hand, has a neutral, mild taste that easily takes on the flavor of whatever seasonings and sauces are used to prepare it.

Which is better, natto or tempeh?

Natto and tempeh are both nutritious soy foods that are high in protein, dietary fiber, and iron, while also providing vitamin K2. They differ in how much selenium and folate they contain, which is why it’s a good idea to include both in your diet if you enjoy both foods. The biggest difference between natto and tempeh is their taste, aroma, and appearance, so the best choice is really the one you enjoy eating the most.

The scientific information in this article was accurate at the time of publishing but may change over time as new research becomes available.

References

  1. Afzaal M, Saeed F, Islam F, et al. Nutritional Health Perspective of Natto: A Critical Review. Biochem Res Int. 2022;2022:5863887. Published 2022 Oct 21. doi:10.1155/2022/5863887
  2. Patterson K, Bhagwat S, Williams J, et al. USDA Database for the Choline Content of Common Foods. Published January 2008. https://www.ars.usda.gov/ARSUserFiles/80400525/data/choline/choln02.pdf. Accessed June 23, 2023.
  3. Boutas I, Kontogeorgi A, Dimitrakakis C, Kalantaridou SN. Soy Isoflavones and Breast Cancer Risk: A Meta-analysis. In Vivo. 2022;36(2):556-562. doi:10.21873/invivo.12737
  4. Cao ZH, Green-Johnson JM, Buckley ND, Lin QY. Bioactivity of soy-based fermented foods: A review. Biotechnol Adv. 2019;37(1):223-238. doi:10.1016/j.biotechadv.2018.12.001
  5. Avilés-Gaxiola S, Chuck-Hernández C, Serna Saldívar SO. Inactivation Methods of Trypsin Inhibitor in Legumes: A Review. J Food Sci. 2018;83(1):17-29. doi:10.1111/1750-3841.13985
  6. Conly JM, Stein K. The production of menaquinones (vitamin K2) by intestinal bacteria and their role in maintaining coagulation homeostasis. Prog Food Nutr Sci. 1992;16(4):307-343.
  7. Capozzi A, Scambia G, Lello S. Calcium, vitamin D, vitamin K2, and magnesium supplementation and skeletal health. Maturitas. 2020;140:55-63. doi:10.1016/j.maturitas.2020.05.020
  8. Ma ML, Ma ZJ, He YL, et al. Efficacy of vitamin K2 in the prevention and treatment of postmenopausal osteoporosis: A systematic review and meta-analysis of randomized controlled trials. Front Public Health. 2022;10:979649. Published 2022 Aug 11. doi:10.3389/fpubh.2022.979649
  9. Li Y, Chen JP, Duan L, Li S. Effect of vitamin K2 on type 2 diabetes mellitus: A review. Diabetes Res Clin Pract. 2018;136:39-51. doi:10.1016/j.diabres.2017.11.020
  10. Reed KE, Camargo J, Hamilton-Reeves J, Kurzer M, Messina M. Neither soy nor isoflavone intake affects male reproductive hormones: An expanded and updated meta-analysis of clinical studies. Reprod Toxicol. 2021;100:60-67. doi:10.1016/j.reprotox.2020.12.019

2 thoughts on “Natto vs. Tempeh: Comparing Two Soy Superstars”

  1. Greetings Stephanie! I must compliment your very thorough comparison of natto and tempeh, along with such overall valuable information. It fact, I was searching other numerous sites looking for the total micrograms of Vitamin K2 in tempeh and yours was the only source that revealed that content in both tempeh and natto!

    Question: I buy my organic tempeh from Trader Joe’s (made with rice, barley and millet) that is fully cooked. I assume that the heat from cooking the tempeh by the manufacturer would be high enough to kill the probiotics in the tempeh? If my assumption is correct, then at least the cooked tempeh would still contain prebiotics, which would be food for our gut bacteria. Also, is the form of K2 in the tempeh the same as the highly beneficial MK-7 found in natto or does it contain another MK variant?

    Sauerkraut jars sold in stores are either refrigerated or stored without being refrigeration. I note that sauerkraut imported from other countries such as Poland are made with cabbage and salt as their only ingredients, yet they do not say they are pasteurized. I will occasionally eat this form of sauerkraut, but I have a question concerning its probiotics and any K2 content.

    Thanks so much!

    1. Hi Jim, thank you for your question!

      Probiotic cultures begin to die when they are subjected to temperatures above 120 °F. However, some good news is that probiotics that have been inactivated by heat are still able to release compounds that exert health benefits. Therefore, probiotics can still positively shift the composition of your gut microbiota despite the exposure to high heat.

      The form of vitamin K2 (MK-7) found in natto is not present in tempeh. Natto contains a species of bacteria known as Bacillus subtilis (not present in tempeh), which is responsible for producing MK-7. Natto is by far the richest source of vitamin K2 (the MK-7 content is 900 µg/100 g).

      Sauerkraut is a less rich source of vitamin K2, although it contains a substantial quantity of vitamin K1. As for probiotics, you will want to buy sauerkraut that is refrigerated, if possible. Sauerkraut that is available in the non-refrigerated sections has most likely been pasteurized or sterilized, meaning the beneficial probiotic microbes have been killed off. Other keywords you can look for on the bottle include “contains live active cultures,” “raw,” or “unpasteurized.”

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