Konjac: A Promising Superfood with Cancer-Fighting Potential and More

Konjac jelly, or konnyaku, is a staple in Japanese home cooking — ubiquitous yet modest in both appearance and taste. It is primarily enjoyed for its chewy texture and ability to absorb the flavors around it, such as in stews.

Despite its long-standing presence in Japanese kitchens, the consumption rate of konjac has remained relatively stable. However, its primary components — glucomannan and ceramide — are linked to a range of health benefits.

Researchers at Gunma University, led by its president, Yasuki Ishizaki, have explored konjac's potential in preventing colorectal cancer and improving diabetes management. Their studies also highlight other health benefits, including improved skin health, enhanced hydration, and a reduced risk of Alzheimer's disease.

As a result, konjac is gaining attention as a potential superfood within the "food is medicine" movement. The university hopes that increasing konjac consumption will also support local farmers.

*Farmers sort konjac tubers dug up for winter storage in November 2024. Showa Village, Gunma Prefecture. (Provided by the Kanto Regional Agricultural Administration Office Gunma Branch)*

Fighting Cancer Cells

In December 2017, Gunma University established the Gunma University Center for Food Science and Wellness. The center's mission is to advance research in food and health and promote local industries, particularly agriculture. A master's program is set to launch in spring 2025.

Key research areas include lifestyle diseases and molecular-level investigations into maintaining brain health for longevity. Uncovering the health benefits of konjac, a traditional ingredient in Gunma, is also a major focus.

The primary component of konjac, glucomannan, is a water-soluble dietary fiber that digests slowly and expands as it absorbs water. In the intestines, it stimulates the intestinal walls and promotes regular bowel movements.

While its digestive benefits are well-known, research shows that glucomannan also nourishes beneficial gut bacteria. This, in turn, may enhance immunity, reduce inflammation, prevent skin conditions, and improve lipid metabolism. These factors could help prevent colorectal cancer.

Experiments at Gunma University found that feeding glucomannan to mice, either through food or water, reduced the incidence of colorectal cancer and suppressed cancer cell survival.

Additionally, researchers discovered a correlation in Yamagata City, where konjac consumption is the highest in Japan, with lower rates of rectal cancer.

Suppressing Blood Sugar Levels

Green Leaf, a company based in Gunma Prefecture, launched a porridge product containing konjac. A study tested the blood sugar-lowering effects of this konjac porridge, which is sold in 250-gram packages for ¥250 JPY (about $1.5 USD).

The study compared blood sugar levels after consuming three types of porridge: a standard porridge and two variations containing 0.4% and 0.8% konjac powder.

Results showed a significant reduction in blood sugar levels, which was proportional to the amount of konjac powder consumed. The effect was particularly strong in individuals at risk of diabetes, suggesting that konjac powder may have promising preventive potential.

A similar study examined triglyceride levels in the blood after consuming konjac porridge. The findings revealed a reduction in triglycerides, although parallel tests with supplements showed less pronounced effects.

Professor Emeritus Masami Murakami, who led the study, noted, "Uncovering the detailed mechanisms behind these effects remains a challenge for future research."

Green Leaf sees global potential for its konjac powder, envisioning its incorporation into rice dishes such as Korean gukbap in Korea, Italian risotto in Italy, and Spanish paella.

Potential for Dementia Prevention

Another health benefit of konjac is ceramide, which plays a crucial role in maintaining skin hydration. It is particularly abundant in konjac derived from raw bulbs, exceeding levels found in many other foods.

As we age, ceramide levels naturally decline — dropping to about half of teenage levels by the age of 50, with further decreases thereafter. Regular consumption of ceramide has been shown to improve skin health and reduce allergic reactions, such as atopic dermatitis.

Research also suggests that ceramide may slow the progression of Alzheimer's disease, which accounts for 70% of dementia cases. Alzheimer's is believed to develop when amyloid-beta, an abnormal protein, accumulates in the cerebral cortex and hippocampus. Ceramide helps prevent this buildup.

Professor Katsuyuki Mukai, a visiting professor at Gunma University and lead researcher, explains, "It takes 15 to 20 years—or even 30 years—for this protein to accumulate enough to cause symptoms." He emphasizes, "Starting regular dietary intake around age 50 can significantly lower the risk of developing the disease."

*Konjac leaves thriving in the summer, while the tubers lie underground, waiting to be harvested in late autumn. (Provided by the Kanto Regional Agricultural Administration Office Gunma Branch)*

Low Consumption Rate in Gunma

Despite its health benefits, the harvest volume, price of konjac bulbs, and spending on konjac products in Japanese cities have steadily declined over the years.

Although Gunma produces over 90% of Japan's konjac, its local consumption is particularly disappointing, according to the Kanto Regional Agricultural Administration Office Gunma Branch.

The 2023 Household Survey by the Ministry of Internal Affairs and Communications ranked Maebashi, Gunma's capital, 45th out of 50 major cities in annual konjac spending. Residents spent just ¥1,392 (about $9), less than half of the top-ranked Yamagata City.

*An oden stew skewer with a triangular piece of konjac (top), sausage wrapped in tofu skin, and fish cake.*

This suggests that the health benefits of konjac remain underappreciated. In an effort to boost its appeal, Gunma University partnered with Asama Kogen Beer, a brewery in Tsumagoi Village, to produce beer made from konjac bulbs.

The beer was sold exclusively at FamilyMart stores in Gunma Prefecture. It was priced at ¥704 (about $4.5) for a 330-milliliter bottle. All 550 bottles sold out quickly by June 2023. In December, an additional 2,000 bottles were stocked across 53 stores in the prefecture. While the beer doesn't offer the same health benefits as konjac porridge, it has sparked renewed interest in the ingredient.

With hot pot season in full swing, why not add more konnyaku or shirataki (konjac jelly noodles) to your dishes and enjoy their health and beauty benefits?