Natto
About Natto
Natto. Fermented whole soya beans, a traditional Japanese food made by inoculating cooked soya beans with Bacillus subtilis var. natto. Sold ready to eat in small polystyrene packs with a distinctive sticky texture and strong, savoury flavour. Available in the UK from Japanese and Asian food shops and some larger supermarkets.
Per 100g, natto provides:
- Vitamin K2 (menaquinone-7): the highest known dietary source. The bacterial fermentation generates the K2 form, which the body uses for blood clotting and bone health alongside K1 from leafy greens.
- Protein, manganese, iron, copper and folate.
Natto is the richest dietary source of vitamin K2 (specifically menaquinone-7). Standard food composition tables, including the source behind the figures here, measure only vitamin K1, so they greatly understate natto's true vitamin K content. Its K2 is the reason natto is of particular interest for vitamin K.
Anyone taking warfarin or another vitamin K antagonist should keep dietary vitamin K steady and avoid sudden additions of high-K2 foods such as natto; speak to the anticoagulant clinic before starting it regularly.
Micronutrients (per 100g, as-eaten)
| Nutrient | Amount | % adult reference intake |
|---|---|---|
| Minerals | ||
| Iron | 8.6 mg | 58% |
| Calcium | 217 mg | 31% |
| Magnesium | 115 mg | 38% |
| Potassium | 729 mg | 21% |
| Sodium | 7 mg | 0% |
| Chloride | not measured | . |
| Phosphorus | 174 mg | 32% |
| Zinc | 3.03 mg | 32% |
| Copper | 0.67 mg | 56% |
| Manganese | 1.53 mg | 109% |
| Iodine | not measured | . |
| Selenium | 8.8 ug | 12% |
| Vitamins | ||
| Vitamin A | 0 ug | 0% |
| Vitamin C | 13 mg | 33% |
| Vitamin D | 0 ug | 0% |
| Vitamin E | 0.01 mg | 0% |
| Vitamin K | 23.1 ug (K1 only1) | see note |
| Vitamin B1 (thiamin) | 0.16 mg | 16% |
| Vitamin B2 (riboflavin) | 0.19 mg | 15% |
| Vitamin B3 (niacin) | 0 mg | 0% |
| Vitamin B5 (pantothenic acid) | 0.22 mg | 3% |
| Vitamin B6 | 0.13 mg | 9% |
| Vitamin B7 (biotin) | not measured | . |
| Vitamin B9 (folate) | 8 ug | 4% |
| Vitamin B12 | 0 ug | 0% |
Source: USDA SR Legacy, fdc 172443 (matched record: "Natto"). N = present but not quantified; Tr = trace; not measured = no value in the source.
1 The stored vitamin K is phylloquinone (K1) only, because the USDA source does not track menaquinone. Natto's headline vitamin K is K2 (menaquinone-7), the highest known dietary source. See the description for the K2 picture.
What this food is a source of
High in by content (per 100g): Manganese (109%), Iron (58%), Copper (56%), Magnesium (38%), Vitamin C (33%), Zinc (32%), Phosphorus (32%), Calcium (31%).
A source of by content (per 100g): Potassium (21%), Vitamin B1 (thiamin) (16%).
These figures are the amount in the food. How much the body absorbs can vary, see each nutrient's entry for detail.