Stinky, Slimy and Stringy, but the Healthiest Soyfood Ever

There’s nothing natty about natto. This old fashioned soy product is made from whole soybeans that have been soaked, boiled or steamed, and then fermented. It’s known for its sticky coat, cheesy texture, musty taste, sliminess, stringiness and pungent odor. Healthwise, it’s good for us and one of the “good old soys.”

Natto first appeared in northeastern Japan about a thousand years ago. Traditionally, it smelled like straw because it was made by inoculating whole cooked soybeans with Bacillus subtilis or Bacillus natto and incubated in straw. The straw also absorbed the none-too-fragrant ammonia-like odor. Because of frequent contamination by unwanted microorganisms, natto makers abandoned the straw method in favor of inoculating the cooked beans with B. natto, then mixing and packing the product in wooden boxes or polyethylene bags.

Natto is one of the few fermented soy products in which bacteria predominate over the fungi. It’s made the news as the very best source of vitamin K2. The runners up are all animal foods such as goose and chicken liver, cheese, egg yolk, bacon and butter. Natto beats all of them by far though we can certainly get plenty vitamin K2 with a rich and varied WAPF diet containing those foods.

K2 is a fat-soluble vitamin best known for its roles in blood clotting and healthy bone formation and preservation.

There are only two studies that convincingly suggest soy might prevent osteoporosis, and, unfortunately for the soy industry, the only soy food that seems to do that is natto. The bone building, of course, doesn’t come from the miracle bean itself, but from the vitamin K2 manufactured by the bacteria involved in the fermentation process. Vitamin K2 is conspicuously absent from tofu, soy milk or other soybean products, and researchers have found no significant or consistent association between their intake and bone mineral density despite the soy industry’s grand hope of finding a bone-building elixir in the phytoestrogens.

Natto is also the source for nattokinase, an enzyme sold as a supplement and recommended by many alternative MDs for cardiovascular and circulatory problems.

Ready to try natto for its health benefits? It’s most often served with mustard and soy sauce, or used in soups and spreads in Japanese cuisine. But don’t expect it to be widely available in stores here anytime soon. It’s definitely an acquired taste, and a little goes a long way. Children love it―not for its strong, rotten flavor―but because its glistening threads can be stretched, making it one of the all-time great play foods. As for them actually eating it, well, not likely, at least not in the U.S.

Indeed, natto isn’t even popular in all parts of Japan. In areas where it is popular, many restaurants require patrons to sit in a private area so as not to offend other diners with the distinctive smell. You could say natto is the durian of soy foods, though most people who get past the smell of durian come to love it. With natto, that’s not often the case.

Why’s that? I’ll let the irrepressible Anthony Bourdain―the brave man who willingly eats insects, live cobra and just about everything else―explain how he was defeated by natto:

“What I was not ready for, and never will be, was natto . . . an unbelievably foul, rank, slimy, glutinous and stringy goop of fermented soybeans. . . . If the taste wasn’t bad enough, there’s the texture. There’s just no way to eat the stuff. I dug in my chopsticks and dragged a small bit to my mouth. Viscous long strands of mucuslike material followed, leaving numerous ugly and unmanageable strands running from my lips to the bowl. I tried severing the strands with my chopsticks, but to no avail. I tried rolling them around my sticks like recalcitrant angel-hair pasta. I tried slurping them in. But there was no way. I sat there, these horrible-looking strings extending from mouth to table like a spider’s web, doing my best to choke them down while still smiling . . . All I wanted to do now was hurl myself through the paper walls and straight off the edge of the mountain. Hopefully, a big tub of boiling bleach or lye would be waiting at the bottom for me to gargle with.”

That about sums it up, but for one thing. Bourdain calls natto “the Vegemite of Japan,” but unlike Vegemite, natto is actually very good for you!



Is there no end to the foods and other products that can get soy-led? Probably not, and these days soy could be lurking anywhere and everywhere. Although soy can seem like a renewable “green alternative” to petroleum products, the soy-ling of America is bad news indeed for people with severe soy allergies.
In the past, I’ve published the names of common food products likely to contain soy, and exposed many of the aliases soy can hide under—hydrolyzed plant protein, textured vegetable protein, lecithin and bouillon, for starters. The good news for consumers is the Food Allergen Labeling Act of 2006 requires food manufacturers to clearly spell out “s-o-y” on food labels. Even so, I never cease to be amazed at what I find. I expect the “dirty dozen” exposed here will be a surprise to many.
1. Cast iron cookware. Lodge cast iron cookware has been a symbol of old-fashioned quality for more than 100 years. The new ones, however, come pre-seasoned with, guess what? Yup, soy oil. Other “pre-seasoned” brands too? Probably. What did our do-it-yourselfer ancestors season with? Good old fats like tallow.
2. Melt Away Cupcake Liners. Weary of peeling paper off your cupcakes or muffins? Then some prize-winning students at Purdue University have just the thing for you. Their entry in the Student Soybean and Corn Innovation Contest of 2009 was a “melt away” liner that disappears like magic right into the cupcake itself. In other words, “Not in your trash. Trash down the hatch.”
3. Celestial Seasonings Tea. Black cherry, and maybe some other flavors too, contains soy lecithin. And if the celestial ones are soy-ling tea, other brands may be doing so too.
4. White Russians. Did you know there are vegan bars where the White Russians are made with soymilk? If your friendly neighborhood bar has gone vegan, count on cream drinks getting soy-led.
5. Salt Answer RX. This Jimoto product is made up of modified potato starch, artificial flavor, monoammonium glutamate, sucrose, lactic acid, citric acid, hydrogenated soybean oil, silicone dioxide, calcium lactate and maltodextrin. What to do instead, how about salt? Old-fashioned salt. Big Pfood warns us to get off salt right now for a lot of reasons and allegedly for our own good. The truth is the new salt substitutes are addictive and profitable as they make people want to eat, eat and eat some more.
6. Vaccines. Most health conscious people already know about the mercury and/or aluminum found in vaccines. Less well known is that the industry has been turning to soy adjuvants. It may be in the chicken pox vaccine, among others.
7. Pâtés. Chicken, duck and goose liver pâtés at Whole Foods Market look like the real thing — and are priced like a real thing—but may contain soy protein isolate, among other dubious ingredients. Why? To increase profits, obviously, but maybe also to put its upscale consumers in touch with the common folk. SPI, after all, is found in Bumblebee and other supermarket brands of canned tuna. As it happens, the soy industry plans a future of soyled ham, chicken, turkey and other meats. Solbar’s “novel” new soy protein ingredients will “improve mouth feel and overall product quality through their low viscosity and strong gelling properties.” And that’s not all folks! This “novel” technology will allow “smoother injection machine entry.”
8. Instant Oatmeal . Believe it or not, ingredients can include soy protein isolate, partially hydrogenated soy oil, high fructose corn syrup and other goodies. Who would have thunk it? Read those labels. With oatmeal, at least, we still have the right to know when it’s no longer Grandma’s oatmeal.
9. Soft drinks. Mountain Dew, Squirt, Fanta Orange and other citrusy sodas may contain brominated vegetable oil, a product developed as a flame retardant. Now why might brominated vegetable oil (probably from soy oil) be in soda? To keep the other hazardous ingredients from spontaneously combusting? Nope. It’s to emulsify the citruslike flavors. Wouldn’t want them separating and floating to the surface now, would we?
10. Artificial fire logs. Soy, and lord knows what else, might end up in the smoke we breathe. Soy candles are billed as “clean burning” but might also be a problem for people with soy allergies.

Corkboards and floor mats. New versions made out of soy and/or corn may soon set foot in the marketplace. Probably not a problem except for people with contact allergies who touch them with bare hands or feet. Others will experience no problems unless they eat them. Chew on a soy/corn corkboard or floor board? Don’t laugh. Jacob Smoker, one of the Purdue students who invented this prize-winning new product, bit into it and reported it to be “really sweet.” Good to know if your stomach is rumbling, the fridge is empty, you aren’t allergic to soy, and not the least bit fussy about taste and texture. While I can’t imagine ever being so tempted, I do have a concern: If cork can be soy-led, will wine corks be next?



1. The Whole Soy Story: The Dark Side of America’s Favorite Health Food (New Trends, 2005) Chapter 5: Soybeans with Culture.

2. A Cook’s Tour: Adventures in Extreme Cuisine by Anthony Bourdain (Bloomsbury, 2001), p. 152.

3. Ikeda Y, Iki M, Morita A, Kajita E, Kagamimori S, Kagawa Y, Yoneshima H. Intake of fermented soybeans, natto, is associated with reduced bone loss in postmenopausal women: Japanese Population-Based Osteoporosis (JPOS) Study. J Nutr. 2006 May;136(5):1323-8.

4. Fujita Y, Iki M, Tamaki J et al. Association between vitamin K intake from fermented soybeans, natto, and bone mineral density in elderly Japanese men: the Fujiwara-kyo Osteoporosis Risk in Men (FORMEN) study. Osteoporos Int. 2012 Feb;23(2):705-14. doi: 10.1007/s00198-011-1594-1.

For more on vitamin K2 read “On the Trail of the Elusive X Factor: A Sixty-Two Year Old Mystery Finally Solved” by Chris Masterjohn as well as other articles by him.

Kaayla T. Daniel, PhD, CCN, is The Naughty NutritionistTM because of her ability to outrageously and humorously debunk nutritional myths. A popular guest on radio and television, she has appeared on The Dr. Oz Show, ABC's View from the Bay, NPR's People's Pharmacy and numerous other shows. Her own radio show, "Naughty Nutrition with Dr. Kaayla Daniel," launches April 2011 on World of Women Radio. Dr. Daniel is the author of The Whole Soy Story: The Dark Side of America's Favorite Health Food, a popular speaker at Wise Traditions and other conferences, and recipient of its 2005 Integrity in Science Award. Her website is and she can be reached at

3 Responses to Stinky, Slimy and Stringy, but the Healthiest Soyfood Ever

  1. Jeremy Burchett says:

    Interested in using natto supplement for vitamin k-2. There seem to be two types: Nattokinase and k-2 (mk-7). Will the nattokinase even contain K-2? Any idea about how much k-2 or nattokinase we should take on a daily basis?

  2. James says:

    I recommend everyone try natto. It is not that bad at all. There is nothing to fear especially after you have eaten it once and know what to expect. I bought 4 styrofome containers of natto for $3.00. It comes frozen with a little mustard pak and another pak of some type of sauce. Actually any bad ingrediants are in these packets so I don’t use them. I bought them at the local asian market called Top Quality. I stirred it because they say that helps activate the enzymes and amino acids and that will bring out the stringy stuff. It does not smell that bad at all. First I ate it plain. It has a musty cheesy taste. You get used to the stringy stuff. The second time I put the natto on top of a piece of toast. The only thing I read bad about it is it has a much higher omega 6 content than omega 3 so take some fish oil pills or add the salmon into your diet. Natto is very, very do-able though. Go for it!!

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