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Natto

Natto as a functional food: fermented soybeans, very high vitamin K and the warfarin caution, and why proper evidence for health effects was not found.

Content last updated . This page has not been medically reviewed.

Safety first. Supplements can cause side effects and interact with medicines. Read mushroom safety and interactions before you use any mushroom product.

Overview

Natto is steamed soybeans fermented with Bacillus subtilis; it has a strong smell and sticky texture. Natto is different from nattokinase supplements, which are an enzyme product and not covered here.

What the research shows

Proper evidence was not found for natto as a food in the sources we read. PubMed has records that mention natto, but many concern nattokinase or extracts (see Research), and we have not treated them as food evidence.

Safety and individual considerations

  • Warfarin: patient-education pages list natto among foods very high in vitamin K, and advise keeping vitamin K intake consistent while on warfarin. Ask your anticoagulation clinic before changing how much you eat. [1]
  • Soy allergy applies.
  • MAOI antidepressants: ask your clinician about fermented foods. [2]

Related

Leafy greens · Safety

Frequently asked questions

Can I eat natto on warfarin?

Do not change it without asking your anticoagulation clinic. Natto is listed among high vitamin K foods. [1]

References

  1. Cedars-Sinai. For Warfarin: Eating a Consistent Vitamin K Diet. Patient education page; ask your anticoagulation clinic for your own plan.
  2. Mayo Clinic. MAOIs and diet: Is it necessary to restrict tyramine?.
Education, not medical advice. This page is for general information. It does not diagnose or treat any condition and is not a substitute for care from a qualified health professional. Natural does not automatically mean safe. Ask a clinician or pharmacist before changing your care, especially if you take medication, are pregnant or breastfeeding, or have a health condition.