After forty, more people check labels and look into what is really in the fermented soy they have been eating for years without a second thought. In Zielona Góra we produce natto from certified organic soy, so I know its composition inside out. I have gathered here what our natto really contains and how to include it conveniently in the menu, without promises about age, energy or longevity, because natto simply does not make such claims.
⚠️ Are you taking anticoagulant medication (for example acenocoumarol or warfarin)? Natto is one of the richest natural sources of vitamin K, which may affect how these medicines work. Consult your diet and supplements with a doctor. See the important legal and medical information.
In short
- Natto is fermented soy, one of the richest dietary sources of vitamin K2 MK-7.
- Vitamin K contributes to normal blood clotting and to the maintenance of normal bones (authorised EU claims, Regulation 432/2012).
- Natto also provides plant protein with a complete amino acid profile, fibre and soy isoflavones.
- Nattokinase and isoflavones are natural components of fermentation that have no authorised health claim in the European Union, which is why we describe them only in terms of composition.
- It is an everyday food that can be included in a varied diet at any age.
What natto contains
Natto is made from soy beans fermented with the bacterium Bacillus subtilis var. natto. This process changes the composition of the bean: vitamin K2 MK-7, free amino acids and enzymes such as nattokinase appear, and soy protein becomes easier to digest than in the raw bean. With age, nutritional needs change, which is why more and more people over the age of 40 pay attention to the nutritional density of their meals, not just their caloric content.
Vitamin K2 MK-7 and the origin of its name
The name vitamin K comes from the Danish word “Koagulation”, meaning coagulation. It was given in the 1930s by the Danish biochemist Henrik Dam, who was studying blood clotting in chickens fed a fat-free diet. For this discovery he received the Nobel Prize in Physiology or Medicine in 1943. Vitamin K2 is a group of compounds called menaquinones, and MK-7, the long side-chain form, is produced mainly where bacterial fermentation takes place, which is precisely during the production of natto. This is why natto is among the richest natural sources of MK-7 in the everyday diet.
Plant protein, fibre and soy isoflavones
Soy protein, from which natto is made, has a complete profile of essential amino acids, that is those the body does not produce on its own. This is a rare feature among plant proteins. Natto also provides fibre from soy beans and isoflavones, polyphenols that fermentation partly transforms into free forms called aglycones. This is a description of structure and composition, not a promise of action.
| Component | What it is | Origin in natto |
|---|---|---|
| Vitamin K2 MK-7 | Long-chain menaquinone | Product of bacterial fermentation |
| Nattokinase | Proteolytic enzyme | Produced during fermentation |
| Plant protein | Complete essential amino acid profile | Soy bean |
| Soy isoflavones | Polyphenols, partly in aglycone form | Natural component of soy |
Where natto comes from
The characters 納豆 combine two signs: 豆 (tō), meaning bean or soy, and 納 (nō), which in ancient Japan meant storing or offering, including in temple granaries. Hence one of the etymologies of the name: “bean from the granary”. A popular legend attributes the discovery of natto to Minamoto no Yoshiie, an 11th-century Japanese commander, whose cooked soy for horses reportedly fermented in straw bags during a military campaign. The bacterium responsible for this fermentation, naturally present on rice straw, is today the strain Bacillus subtilis var. natto cultivated under controlled conditions.
How to include natto in the diet after 40
The taste of natto is distinctive, nutty and slightly pungent, which is why it is worth starting with small portions. It combines well with neutral or slightly sour products, which softens its aroma:
- with warm (not hot) rice and a little soy sauce,
- as an addition to salads or wraps,
- mixed with garlic and olive oil as a breakfast spread,
- with beetroot and ginger as a snack.
Fresh natto should not be strongly heated, above about 50°C, because high temperature lowers the vitamin K2 content and destroys the enzyme structure. This is a note about the durability of the ingredients, not a health effect. Two to three portions a week are enough for natto to become a regular part of the menu, regardless of age.
Our dried natto with vitamin K2 MK-7 and D3
If you are looking for a ready-made form of our natto, we have prepared tablets that combine natural vitamin K2 MK-7 from dried natto with added vitamin D3. Vitamin D contributes to the normal absorption and utilisation of calcium and phosphorus, contributes to the maintenance of normal bones, contributes to normal muscle function and to the normal function of the immune system. We produce them in Zielona Góra from certified organic soy.
See our dried natto with K2 MK-7 and D3
Safety and precautions
Natto is a food safe for most healthy people. Due to its high vitamin K content, it is worth taking precautions in several situations.
This applies first and foremost to people taking anticoagulant medicines from the vitamin K antagonist group (for example warfarin or acenocoumarol), because vitamin K can affect how these medicines work. Consult your treating doctor about consuming natto and supplements containing vitamin K2. Caution is also advisable during pregnancy and breastfeeding and when taking other medicines regularly. Natto contains soy, so it is not intended for people with a soy allergy. A food supplement or any food product does not replace a varied diet and a healthy lifestyle.
Summary
Natto is fermented soy with a dense nutritional profile: vitamin K2 MK-7, complete plant protein, fibre and isoflavones. Vitamin K contributes to normal blood clotting and to the maintenance of normal bones, and vitamin D3 from our tablets additionally contributes to the normal absorption and utilisation of calcium and phosphorus, to normal bones, muscles and the immune system. After the age of 40, natto is worth treating as an element of a varied diet, not as a solution for age, energy or longevity, because we do not attribute such effects to it.
Frequently asked questions
How often is it worth eating natto?
Most often two to four times a week. Regularity is sometimes more important than a one-off quantity.
Can natto be eaten on an empty stomach?
Yes, for example with rice or vegetables. This is a matter of individual taste preferences.
Does natto contain a lot of salt?
Natto itself has a low sodium content. Salt may, however, come from the accompanying soy sauce or other additions.
Can natto be combined with K2 or D3 supplements?
Natto itself provides vitamin K2 MK-7. Our tablets additionally combine it with vitamin D3. Combining with other supplements is worth discussing with a doctor, especially when taking anticoagulant medicines.
Is natto suitable for people taking blood medicines?
Due to the vitamin K content, people taking anticoagulant medicines should consult their treating doctor about consuming natto.
Does natto have an authorised claim in the European Union concerning ageing, energy or longevity?
No. Natto has no authorised health claim in the European Union concerning ageing, energy or longevity (Regulation (EC) 1924/2006). Authorised claims apply only to vitamin K (blood clotting, normal bones) and vitamin D in our tablets (absorption of calcium and phosphorus, bones, muscles, immune system). Beyond that, we describe natto only in terms of its composition.
Sources
- Regulation (EC) No 1924/2006 and Regulation (EU) No 432/2012; EU Register of Nutrition and Health Claims.
- EFSA (European Food Safety Authority).
- USDA FoodData Central.
Legal and medical note. This article is educational and does not replace the advice of a doctor or pharmacist. Beyond the authorised claims for vitamin K (blood clotting, normal bones) and vitamin D (absorption of calcium and phosphorus, bones, muscles, immune system), we do not attribute any additional health effects to natto or our products, including any effect on ageing, energy or longevity (Regulation (EC) 1924/2006). A food supplement is not a medicine and does not replace a varied diet. Full information is on the Legal and medical information page.
