Understanding the Common Risks and Side Effects
While natto is a powerhouse of nutrition, it is not without potential downsides, particularly for certain groups of people. Understanding these risks is crucial for safe consumption.
Risk of Interaction with Medications
One of the most significant concerns surrounding natto is its interaction with medications, especially blood thinners. The enzyme nattokinase, produced during the fermentation process, has potent fibrinolytic (clot-dissolving) properties, essentially acting as a natural blood thinner. Additionally, natto is one of the richest food sources of Vitamin K2, a nutrient essential for blood clotting. This creates a complex situation for individuals on anticoagulant drugs like Warfarin, which require careful regulation of vitamin K intake. The varying levels of vitamin K2 in natto can destabilize the effect of these medications, potentially leading to dangerous bleeding or excessive clotting. For this reason, anyone on such medication should consult their doctor before consuming natto.
Furthermore, natto's nattokinase may lower blood pressure. This can pose a risk for individuals already on blood pressure medication, as the combined effect could cause blood pressure to drop too low. It is essential for these individuals to monitor their blood pressure closely and discuss the dietary change with a healthcare provider.
Digestive Concerns and Allergies
For those new to natto, digestive issues are a common side effect. The high fiber content, while beneficial in the long run, can cause gas, bloating, and diarrhea as the body adjusts to the change in gut flora. Starting with very small portions and gradually increasing intake can help minimize these symptoms. In rare cases, individuals without a general soy allergy may develop a specific late-onset hypersensitivity reaction to natto, but this is uncommon. Of course, anyone with a known soy allergy should avoid natto entirely, as it is a fermented soybean product. Symptoms can range from mild rashes to severe allergic reactions.
Considerations for Thyroid Health
Soy is considered a goitrogen, a substance that can interfere with the normal function of the thyroid gland. While the effect is typically mild in healthy individuals, it is a concern for people with hypothyroidism, or an already impaired thyroid. The fermentation process in natto may reduce the level of goitrogens, but caution is still advised. Anyone with a thyroid condition should consult a doctor before incorporating natto into their regular diet.
Special Population Groups
Certain individuals should be particularly cautious or avoid natto altogether:
- Pregnant and Breastfeeding Women: Due to a lack of sufficient data on safety, consumption should be limited to food amounts, or avoided.
- Children and Adolescents: Similar to pregnancy, there is insufficient study data to recommend nattokinase supplements, and caution is advised for regular consumption of the food.
- Pre-Surgery Patients: Because of its blood-thinning properties, consuming natto should be stopped at least two weeks before any scheduled surgery.
Natto vs. Nattokinase Supplements: A Comparison
Nattokinase supplements are available for those who want the heart health benefits of the enzyme without consuming the whole fermented food. However, there are important distinctions to be aware of.
| Feature | Whole Natto | Nattokinase Supplement |
|---|---|---|
| Form | Fermented soybean food | Powder, capsule, or tablet |
| Key Components | Probiotics, high Vitamin K2, fiber, protein, nattokinase | Concentrated nattokinase enzyme, often with Vitamin K2 removed |
| Effect on Blood | Combines blood-thinning effect (nattokinase) and clotting effect (Vitamin K2) | Primarily blood-thinning effect |
| Medication Interaction | High risk, especially with Warfarin and other anticoagulants | Moderate to high risk, especially with anticoagulants and blood pressure medication |
| Best For | Healthy individuals seeking diverse nutrients and probiotics | Individuals seeking the targeted effects of the enzyme, only under medical supervision |
Is Natto for Everyone? Balancing Benefits and Risks
For the average, healthy individual, the benefits of natto generally outweigh the risks. The high protein, fiber, and probiotic content support gut health, while Vitamin K2 is beneficial for bone health. The risks, when managed correctly, are minimal. However, individuals with pre-existing conditions, particularly cardiovascular or thyroid issues, or those on certain medications must approach natto with caution and medical guidance. Always be transparent with your doctor about all dietary changes and supplements, especially if they are potent as natto. The key to incorporating this unique superfood into your diet safely is moderation and an understanding of your own health needs. For most, a small serving a few times a week is an excellent way to reap its nutritional rewards without undue risk.
The Role of Moderation and Preparation
To minimize potential side effects, start with a small amount of natto, perhaps a tablespoon mixed with rice, and observe how your body reacts. You can gradually increase the portion size over time. The fermentation process makes the nutrients in natto more bioavailable and easier to digest than unfermented soy, so it is often better tolerated than other soy products. Some people find the distinctive taste and texture to be a hurdle. Mixing natto with other strong flavors, such as a traditional sauce, mustard, or kimchi, can help mask the intensity. Freeze-dried natto is also an option for those who want the benefits without the typical stringy, sticky texture.
Conclusion
Natto, a venerable fermented superfood from Japan, offers a compelling profile of nutrients that support heart, bone, and digestive health. The enzyme nattokinase and high vitamin K2 content are particularly noteworthy for their potential benefits. However, it is precisely these potent components that also give rise to the most significant side effects, primarily the risk of interaction with blood-thinning medication. Digestive issues, soy allergies, and thyroid concerns are also valid considerations. For the general population, natto is a healthy and safe addition to a balanced diet, provided it is consumed in moderation. Those with specific medical conditions must consult a healthcare professional to determine if natto is appropriate for them. By understanding the potential risks and practicing moderation, many people can enjoy the remarkable health benefits of this unique and ancient food. For more detailed information on nattokinase in supplements, see this resource from Drugs.com, though always consult a doctor.
