Interesting facts about the bacteria found in Japan's favourite fermented food, natto

Natto on rice. (Photo: Getty Images)

It seems that rumours about how strong the bacteria in natto is have been floating around the Internet space of Japan. For those who know nuts about natto, it is fermented soy beans, known for its sticky texture and pungent smell. So, how strong, really, is this bacteria?

Some say natto bacteria is so strong that the food industry is banning consumption of natto. Others added that the natto bacteria is even more resilient than one of the most resilient animals known, Tardigrade — a water-dwelling, eight-legged, micro-animal – such that it will not die even in a harsh environment.

But how true are these rumours? We separate fact from fiction for you.

Natto bacteria is so strong, there are companies in the food industry that ban the consumption of natto. — True.

The consumption of natto is known to be banned at places like soy sauce factories, bakeries, biological laboratories, and even sake breweries. One of the reasons is the bacteria’s reproduction speed. Compared to other bacteria, the natto bacterium cell divides faster. It can reproduce up to 4 billion cells from just one cell in 16 hours!

In an environment suitable for breeding and growth, natto bacteria may adversely affect the reproduction of lactic acid bacteria, yeast and the like. Some breweries that accept visits also put up a notice saying natto bacteria has a negative influence on the making of sake and that visitors are advised to avoid having natto for breakfast on the day of visit.

Natto bacteria does not die even in boiling water. — Partially true.

It is true that the bacteria have resistance towards heat. However, when placed in boiling water for 10 minutes, most of them would die.

Natto bacteria does not die even when irradiated with a gamma dose equivalent to 3,000 times the lethal dose for humans. — Unknown.

The bacteria will die under gamma radiation, but specifically how much is not known.

Even when the source of nutrients is depleted, natto bacteria can still live for more than 1 million years. — Unknown.

The possibility cannot be denied, but there is no proof yet.

Natto bacteria can withstand vacuum. — True.

Natto bacteria can be freeze-dried (in vacuum state) and stored. However, this seems to apply to other bacteria too.

Natto bacteria survive even in outer space. — Maybe.

This cannot be known for sure as no research has been done on this, but it is possible the bacteria came from outside Earth. This is based on the fact that natto bacteria has tolerance towards minerals found near the Earth’s mantle, which is a feature not seen in other bacteria.

If natto bacteria only exist on the ground, it is unnatural for it to have such a property. From that, people are speculating it may have been an extraterrestrial creature on a meteorite that landed on Earth a long time ago. Perhaps, if scientific evidence can be obtained, this theory will have higher credibility. But for now, we can only await the future research results.

Natto bacteria has resistance towards strong acidic gastric juice and can survive until they reach the intestines. — True.

Most of the bacteria is thought to reach the intestines without dying. Among the above seven factoids regarding how strong natto bacteria is, only three are true. The rest hover around being partially correct or the truth is unknown. While natto bacteria’s reproduction and resistance levels are apparently strong, the rumours have been too extreme for investigation to be conducted.

But at least, the following are all true:

  • Natto bacteria does not die from gastric juice. Some would ferment in the intestines and create an environment for good bacteria to reproduce.
  • Due to its reproductive strength and other factors, natto bacteria can be expected to suppress breeding of pathogenic bacteria in the body.
  • Due to its benefits, a military doctor of the Japanese Navy published a book titled “Natto Prevalence is Now an Urgent Need” (1942).
  • Originally a food unique to the Kanto and Tohoku region, natto became common nationwide after the war.

Perhaps, the real power and strength of natto bacteria is not found in outer space or the vacuum, but in our stomachs. Yum.

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