Natto: The Japanese Fermented Soybean and Its Cognitive Benefits
Among the many ingredients in the traditional Japanese diet, one bean stands out in its potential to aid with memory loss: natto. This food is made from soybeans that have been fermented with the bacteria Bacillus subtilis var. natto, giving it a distinctive sticky texture, strong smell, and a powerful nutritional profile. While the taste can be an acquired one, the health benefits have been celebrated for centuries and are now being substantiated by modern research.
Key Brain-Boosting Components in Natto
Numerous compounds in natto work synergistically to support cognitive function:
- Nattokinase: This enzyme is a potent fibrinolytic agent, meaning it helps break down blood clots and improves blood flow. Better cerebral blood flow is crucial for delivering oxygen and nutrients to the brain, which in turn supports cognitive abilities and overall brain health. A recent preclinical study suggests that nattokinase supplementation can improve cognitive ability by protecting the blood-brain barrier.
- Isoflavones: As with all soy products, natto is rich in isoflavones, plant-based compounds with antioxidant and anti-inflammatory properties. Research indicates that fermentation increases the bioavailability of these isoflavones, making them more readily absorbed by the body. Some studies have found that soy isoflavones may improve memory, particularly in older women, by mimicking the effects of estrogen in the brain.
- Probiotics: The fermentation process turns natto into a potent source of probiotics, which play a vital role in the gut-brain axis. A healthy gut microbiome has been linked to stronger cognitive function and reduced neuroinflammation, which is a contributing factor to cognitive decline.
- Brain-Derived Neurotrophic Factor (BDNF): Animal studies have shown that natto can restore the natural production of BDNF, a protein that plays a key role in building new brain cells and improving learning and memory.
- Lecithin: Soybeans, and thus natto, contain lecithin, a compound essential for the production of acetylcholine, a key neurotransmitter involved in memory.
Fermented vs. Unfermented Soy for Brain Health
While all soybeans offer nutritional value, the fermentation process in natto provides distinct advantages for cognitive health, as highlighted in studies on isoflavone bioavailability and probiotic content. Here is a comparison:
| Feature | Fermented Soy (Natto) | Unfermented Soy (Edamame, Tofu) |
|---|---|---|
| Isoflavones | Higher bioavailability of aglycone isoflavones, which are more readily absorbed by the body. | Contain isoflavones in glycoside form, which have lower bioavailability. |
| Probiotics | Excellent source of beneficial bacteria (probiotics) from the fermentation process. | Does not contain probiotics; benefits are limited to the bean's inherent nutrients. |
| Nattokinase Enzyme | Unique to natto and other fermented soy products; provides powerful blood flow benefits. | Not present. The enzyme is created during fermentation. |
| Nutrient Enhancement | Fermentation increases nutrient content and promotes antioxidant effects. | Good source of protein, fiber, and general minerals, but lacks the specific benefits of fermentation. |
Other Japanese Beans and the Broader Diet
While natto receives significant attention, other beans and foods in the traditional Japanese diet also contribute to brain health.
Adzuki Beans and Antioxidants
Research into adzuki beans has shown promise for cognitive function, particularly in animal models of Alzheimer's disease. An extract from adzuki beans was found to inhibit the formation of amyloid-β aggregates and delay cognitive impairment in Drosophila models. This is attributed to the bean's rich content of polyphenols, which suppress oxidative stress and inflammation—both major factors in age-related cognitive decline. The high antioxidant content places adzuki beans among a class of foods that can help protect brain cells from damage.
The Holistic Approach of the Japanese Diet
It is also important to consider that the overall dietary pattern in Japan, not just a single ingredient, is associated with a lower risk of dementia. The traditional Japanese diet is rich in fish (high in omega-3 fatty acids), vegetables, seaweed, and green tea, all of which contribute to a healthy brain. A 2024 study on Japanese women found that those adhering to a traditional Japanese diet experienced less brain atrophy compared to those on a Western diet. The synergistic effect of these diverse, nutrient-dense foods likely plays a significant role in promoting cognitive longevity.
Conclusion
While a single food cannot be a cure for memory loss, the fermented Japanese soybean, natto, presents a compelling case for its role in supporting brain health. Through its unique combination of isoflavones, nattokinase, probiotics, and BDNF-promoting effects, natto can help improve blood flow, reduce inflammation, and enhance neural communication. Though some human trials have shown modest results, particularly in older women, the robust animal and preclinical research suggests a strong potential for mitigating age-related cognitive decline. As research continues, the cumulative evidence points toward natto as a potent dietary aid, best consumed as part of a broader, brain-healthy Japanese dietary pattern that includes other beneficial foods like adzuki beans. Individuals seeking to support their cognitive function may consider incorporating this traditional superfood into their diet.
For more detailed research on the effects of natto, including its impact on specific signaling pathways in the hippocampus, see the study published by the Royal Society of Chemistry.
