Natto, the distinctively pungent and sticky Japanese superfood, has garnered global attention for its potential health benefits, especially concerning metabolic health. Made from soybeans fermented with Bacillus subtilis natto, this traditional staple may play a beneficial role in managing blood sugar levels and other complications associated with diabetes. Its unique composition of fiber, protein, probiotics, and vitamin K2 contributes to its potent anti-diabetic properties.
The Science Behind Natto and Blood Sugar Control
Fermented soybean products like natto have been investigated for their ability to combat diabetes and related metabolic issues. The fermentation process increases the bioavailability and quantity of beneficial compounds, making natto more effective than plain soybeans in modulating blood glucose.
How natto affects postprandial glucose
One of natto's key benefits is its ability to help regulate blood glucose levels after eating. A clinical crossover study demonstrated that a natto meal significantly suppressed the rise in postprandial (after-meal) blood glucose compared to a control meal of white rice alone. This effect is partly attributed to natto's low glycemic index and the viscosity provided by its gamma-polyglutamic acid (γ-PGA) content, which delays the absorption of carbohydrates.
The role of gut microbiota
The probiotics in natto, primarily Bacillus subtilis natto, are crucial for gut health. A healthy gut microbiome is increasingly linked to better metabolic function and reduced risk of chronic diseases, including diabetes and obesity. Natto consumption has been shown to modify gut microbiota by increasing beneficial bacteria like Bifidobacterium and Bacilli, and decreasing less desirable strains. This modulation of gut bacteria can lead to improved metabolism and better blood sugar control.
Insulin sensitivity and vitamin K2
Natto is one of the richest food sources of vitamin K2 (menaquinone-7). Research indicates that vitamin K2 supplementation can improve insulin sensitivity and glycemic control, especially in individuals with type 2 diabetes. Vitamin K2 influences glucose metabolism via vitamin K-dependent proteins and its anti-inflammatory effects. A four-week study in healthy young men showed that daily vitamin K2 supplementation improved insulin sensitivity.
Anti-inflammatory and antioxidant effects
Diabetes is often accompanied by systemic inflammation and oxidative stress. Natto contains anti-inflammatory and antioxidant compounds that can combat these issues. By reducing inflammation, natto helps protect the pancreas and supports overall metabolic health, thereby reducing complications associated with diabetes.
Cardioprotective benefits
Individuals with diabetes are at a higher risk for cardiovascular diseases. The enzyme nattokinase, found in natto, has powerful fibrinolytic activity, meaning it helps break down blood clots and improve blood flow. It can also help lower blood pressure, which often co-occurs with diabetes. These effects can help reduce strain on the heart and lower cardiovascular risk factors.
Nutritional Profile: What Makes Natto a Diabetic-Friendly Food?
Natto's nutritional makeup is ideal for managing diabetes due to several key components:
- High Fiber: A cup of natto can contain over 9 grams of dietary fiber. Fiber slows digestion and the absorption of glucose, which prevents sudden spikes in blood sugar.
- Rich in Protein: Natto is a complete protein source, providing all nine essential amino acids. Protein helps with satiety and supports stable blood glucose levels.
- Healthy Fats: The fats in natto are predominantly polyunsaturated and monounsaturated, which are beneficial for heart health and cholesterol management.
- Bioactive Compounds: Beyond probiotics and nattokinase, natto contains isoflavones and γ-PGA, which contribute to its anti-diabetic effects.
Comparison of Natto and Unfermented Soybeans for Blood Sugar
While soybeans are healthy, the fermentation process makes natto more potent for blood glucose control. A key study highlighted this difference, as shown below.
| Feature | Natto (Fermented Soybeans) | Steamed Soybeans (Unfermented) |
|---|---|---|
| Effect on Postprandial Glucose | Significantly suppresses the rise in blood glucose. | Moderately suppresses blood glucose, but less effectively than natto. |
| Viscosity (γ-PGA) | Contains high levels of viscous gamma-polyglutamic acid, which slows glucose absorption. | Lacks the viscous γ-PGA produced during fermentation. |
| Microbiota Modulation | Adds beneficial Bacillus subtilis natto probiotics, altering gut flora. | Does not introduce probiotics in the same way as fermentation. |
| Nutrient Enhancement | Fermentation increases certain nutrient levels and produces unique bioactive compounds like nattokinase. | Nutrients are available but lack the fermented enhancement. |
How to Safely Incorporate Natto into a Diabetic Diet
For most individuals, natto is a safe and healthy addition to a diabetic meal plan. It can be mixed with various ingredients to create palatable dishes. Here are some simple suggestions:
- Traditional Natto Gohan: Mix natto with a small amount of soy sauce, a touch of mustard, and chopped green onions. Serve it with brown rice instead of white rice for better glycemic control.
- Natto with Tofu and Vegetables: Incorporate natto with silken tofu and a variety of non-starchy vegetables for a nutrient-dense, low-carb meal.
- Natto in Miso Soup: Stir natto into a bowl of miso soup to add probiotics and extra protein.
- Natto as a Topping: Sprinkle natto over salads, stir-fries, or avocado toast.
A note on medication
It is crucial for anyone taking blood-thinning medication, such as warfarin, to consult their doctor before adding natto to their diet. The high vitamin K2 content in natto can interfere with these medications and affect blood clotting.
Who Should Be Cautious with Natto?
While highly beneficial for many, natto may not be suitable for everyone:
- Soy Allergies: People with soy allergies should avoid natto, as it is made from soybeans.
- Hypothyroidism: Some research suggests that goitrogens in soy products might affect thyroid function, so individuals with hypothyroidism may need to be cautious and consult their doctor.
- Interactions with Blood Thinners: As mentioned, the high vitamin K2 content requires careful monitoring for those on anticoagulant therapy.
Conclusion: The Final Verdict on Natto for Diabetics
Natto is a highly beneficial food for individuals with diabetes due to its potent ability to regulate blood glucose, improve insulin sensitivity, and enhance gut health. Its rich nutritional profile of fiber, protein, and vitamin K2, along with its unique bioactive compounds like γ-PGA and nattokinase, addresses several key aspects of diabetic health. However, like any dietary change, it is important to consider individual health status, especially regarding medications and allergies. For most, integrating natto into a balanced diet can be a valuable strategy for managing diabetes and promoting overall metabolic wellness.
One study on fermented soybean foods and diabetes can be found at the National Institutes of Health: Fermented soybean foods and diabetes.
