The primary ingredient of natto is soybeans, with a proportion of three main nutrients: fat, carbohydrates, and protein in a ratio of 1:1.5:2. Alongside its abundant high-quality protein content, natto is also rich in nutrients such as calcium, vitamin B1, soy isoflavones, dietary fiber, and more.
Every country has its unique and distinctive foods. In Taiwan, there’s stinky tofu, pork blood cake, and century eggs; Indonesia has civet coffee; France is known for blue cheese; and Japan is no exception. Among the well-known and distinct foods in Japan, the focus of this article is on “natto.”
What is Natto?
For many friends who have traveled to Japan, natto products might be familiar. But what is natto exactly? The earliest method of making natto involved wrapping steamed soybeans in sterilized straw, then fermenting them under controlled temperature and humidity conditions. Nowadays, natto is produced on a larger scale through bioengineering processes that purify “natto bacteria” (Bacillus subtilis natto), which is then used for mass fermentation to create the final product.
In simple terms, natto is a product obtained through the fermentation of soybeans using bacteria.
What are the Nutritional Components of Natto?
The main ingredient of natto is soybeans, and the proportions of its three primary nutrients—fat, carbohydrates, and protein—are roughly in a ratio of 1:1.5:2. In addition to being rich in high-quality protein, soybeans also contain calcium, vitamin B1, soy isoflavones, dietary fiber, and other nutrients.
As we know, natto is made by fermenting soybeans with natto bacteria, which causes significant changes in its chemical composition. Despite these changes, natto retains the original high-quality protein, calcium, vitamin B1, soy isoflavones, dietary fiber, and other nutrients found in soybeans. Furthermore, the fermentation process increases the content of various vitamins, including vitamin B2, vitamin B6, and vitamin K2 . The fermentation process also enhances the total amount of soy isoflavones naturally present in soybeans.
💡In addition to the mentioned nutrients, natto also contains various protein-degrading enzymes. Among them, the most well-known is the fibrinolytic enzyme “nattokinase.” Nattokinase is known for its ability to dissolve blood clots and lower blood pressure .
What are the Recommended Evidenced Benefits of Natto?
In terms of nutrition, natto contains even richer nutrients compared to soybeans, and there are also numerous clinical evidences supporting its benefits.
1. Promoting Cardiovascular Health
Reducing Mortality Due to Cardiovascular Diseases
In a recent study involving adults aged 45 to 74, totaling over 92,000 participants followed for almost 15 years, it was found that the group with the highest natto intake significantly reduced mortality caused by cardiovascular diseases .
The diagram below illustrates the regulatory mechanism of thrombus formation and dissolution.
As mentioned earlier, natto contains a significant protein-degrading enzyme known as “nattokinase,” which is the main component that prevents the formation of blood clots. This is achieved primarily through three mechanisms (highlighted by the green fluorescence markers in the diagram):
- Nattokinase activates tissue plasminogen activator (t-PA), converting plasminogen into plasmin, an enzyme responsible for dissolving blood fibrin.
- Nattokinase further activates urokinase, which in turn activates plasmin.
- Nattokinase can directly degrade the main component of blood clots, fibrin.
This demonstrates nattokinase’s role in promoting cardiovascular health by preventing and dissolving blood clots.
💡Nattokinase can assist in thrombus dissolution, ensuring vascular patency, and preventing blockages in various organs, such as the brain and heart, which can lead to conditions like stroke or myocardial infarction.
Lowering Blood Pressure
Research has explored the relationship between nattokinase and blood pressure, revealing that the intake of nattokinase for a continuous 8 weeks can reduce both systolic and diastolic blood pressure. Furthermore, when compared to the clinical medication aspirin in terms of enhancing blood flow, nattokinase’s efficacy is comparable .
Reducing the Incidence of Arterial Atherosclerosis
In clinical settings, nattokinase can reduce the oxidation of LDL-c (low-density lipoprotein), also known as “bad cholesterol,” decrease triglycerides, and lower total cholesterol levels, thereby reducing the occurrence of arterial atherosclerosis .
2. Contributing to Strong Bones
Natto is rich in calcium and vitamin K2, which aids in bone formation by transporting calcium to the bones and maintaining bone health. Additionally, it can slow down the rate of bone loss. In recent large-scale studies focused on postmenopausal women and their fracture rates, it was found that natto intake might effectively lower the occurrence of fractures caused by osteoporosis by increasing bone density .
3. Maintaining a Healthy Gut and Enhancing the Immune System
Natto bacteria are considered probiotics that help establish a healthy gut microbiota and prevent the growth of harmful bacteria. In a study involving elderly individuals, supplementing with natto bacteria resulted in a lower frequency of respiratory infections compared to the placebo group .
Does Natto Have Side Effects?
Natto bacteria are considered a very safe probiotic strain. The U.S. Food and Drug Administration (FDA) has classified natto bacteria under the “generally recognized as safe” (GRAS) category, indicating that its normal addition to food is considered safe.
Studies have conducted a series of safety tests on nattokinase, including mutagenicity and toxicity experiments, without observing adverse reactions . Additionally, research has established a maximum allowable dose of nattokinase in animals, which can reach up to 480,000 FU (Fibrinolytic Units) per kilogram of body weight .
In summary, natto and its related products are generally safe for consumption. However, due to the lack of safety evidence for pregnant, lactating women, and children, consumption is not recommended.
- Vitamin K present in natto may reduce the effectiveness of anticoagulant medication warfarin, so consuming them together should be avoided.
- For individuals taking antihypertensive medications like ACE inhibitors or calcium channel blockers, nattokinase may enhance the effects of the drugs, potentially causing symptoms of low blood pressure. Thus, combining them should be avoided.
- People with bleeding disorders like hemophilia may experience worsened symptoms with nattokinase consumption, so it should be avoided.
- Note that nattokinase has thrombus-dissolving effects, which can prolong blood clotting time, increasing the risk of bleeding during surgery or post-surgery. Therefore, natto-related products should be stopped before planned surgeries.
How to Consume Natto (Effective Dosage)?
When choosing natto products, the most crucial factor is knowing the content of Fibrinolytic Units (FU). “FU” is an activity unit defined by the Japan Nattokinase Association for the enzyme that dissolves blood clots. For general maintenance, it’s recommended to consume at least 2,000 FU per day per person. For individuals with cardiovascular issues, around 4,000 FU per day is suggested. Consuming products with lower doses than these guidelines might significantly reduce their health benefits.