ヴァータとサツマイモVata and Sweet Potatoes

I have always had a very difficult time with summer due to my physical constitution, and my health tends to fluctuate dramatically and become unstable during the three months from mid-June, when Japan’s hot and humid weather intensifies. Generally speaking, summer is a time for enjoying outdoor activities under the sun, but recent Japanese summers have become so severe that going outside often makes me feel physically unwell. Compared to when I was a child, the intensity of summer now seems to negatively impact health. When autumn arrives after enduring this harsh summer, my activity level surges dramatically. In recent years, I’ve strategically scheduled my research trips around Japan primarily in autumn and spring, while winter has become a season devoted thoroughly to reading, studying, preparation for the coming seasons, and introspection. As such, finding the best way to spend summer is always a great challenge, and this year as well, I’m continuously experimenting on a daily basis.

This struggle isn’t simply a matter of personal seasonal preference but also reflects my inherent constitution. Ayurveda, the traditional medicine system originating from ancient India, states that each person’s innate constitution and physiological functions are governed by three energy principles known as doshas. These doshas are believed to determine one’s prakriti (innate constitution) based on their proportions. The dosha of “ether and air” is called Vata, the dosha of “fire and water” is Pitta, and the dosha of “earth and water” is Kapha.

According to Ayurvedic prakriti, my constitution comprises approximately 90% Vata, the wind dosha, and about 10% Kapha, the water dosha, with no innate presence of Pitta, the fire dosha. Thus, given my overwhelmingly dominant Vata, managing and balancing it throughout my life is crucial for maintaining good health. However, Ayurveda also speaks of vikriti, an acquired constitution influenced by environmental factors and lifestyle. For me, the biggest issue lies precisely here: the overwhelmingly dominant dosha in my vikriti is Pitta, the fire dosha.

Doshas are applied not only to human constitutions but also to various other elements, including the seasons. Currently, we are in the Pitta season, which governs late spring through summer. This inevitably increases Pitta, making this season particularly challenging for me. My already elevated Pitta vikriti interacts synergistically with the harsh summer season, constantly affecting my daily life. Consequently, maintaining physical and mental stability becomes extremely difficult. Even so, my creativity continually overflows, prompting bursts of intense activity followed by rapid energy depletion and extreme exhaustion, creating a recurring negative cycle.

Now, at 34 years old, I feel it’s time to reconsider my relationship with my elevated Pitta vikriti. I wish to ensure my innate prakriti remains dominant and my Vata stays stable, even during summer. According to Ayurveda, dietary habits play a foundational role in achieving this balance. Therefore, determining the ideal dietary approach to summer has become a significant lifelong theme for me.

Reflecting the extreme nature of my Vata constitution, my dietary habits are extremely selective, and it might surprise some to learn that 99% of my meals over 365 days are identical. Furthermore, for the past four years, I’ve typically limited myself to just one meal a day, consumed exclusively at night after completing all tasks. This meal usually consists of a chicken and rice soup along with some nuts, and I rarely consume anything else. Thus, introducing variations to this daily staple soup has become my primary strategy for improvement. Among these variations, sweet potato has proven particularly beneficial.

Although sweet potatoes may pose problems for those with a Kapha dosha, they are an excellent choice for individuals with a Vata dosha, as they help stabilize and calm Vata imbalance. This aligns closely with the macrobiotic diet proposed by Yukikazu Sakurazawa (1893–1966), who systematized dietary principles based on traditional Edo-era food therapy (shokuyo, 食養) combined with the theory of Yin and Yang. In macrobiotics, sweet potatoes are categorized as “slightly yin but relatively balanced (chuyo, 中庸).” Macrobiotic theory emphasizes adjusting the inherent Yin-Yang balance of ingredients through preparation methods; for instance, cooking sweet potatoes in soup shifts their energy toward Yang.

For those with Vata constitutions, consuming cold foods and drinks can exacerbate Vata imbalance, which, in my case, subsequently causes my elevated Pitta vikriti to spiral out of control, necessitating careful attention. Considering this, from this year onward, I’ve resolved to consume only warm soups even during summer. Sweet flavors are essential in stabilizing Vata, making sweet potatoes particularly suitable. Furthermore, this single vegetable—sweet potato—possesses an exceptionally intriguing historical background in Japan.

In Japan, sweet potatoes, originally called kansho (甘藷), are native to Central and South America, including regions such as Mexico and Peru. After Columbus brought them to Europe at the end of the 15th century, they reached Asian regions such as Luzon in the Philippines and southern China by the late 16th century. Consequently, sweet potatoes were virtually unknown in Japan until the 17th century. Their introduction to Japan is believed to have occurred around the early Edo period, specifically around 1604–1605. Interestingly, the transmission route of sweet potatoes is preserved in the very Japanese name used today, satsumaimo. This points to its southern origins.

The history of satsumaimo in Japan began when a Ryukyu Kingdom (modern-day Okinawa) official named Noguni Sokan brought satsumaimo from Fujian Province in China to Ryukyu. Originally, Ryukyu’s land was unsuitable for wet rice cultivation, which was prevalent on mainland Japan, so their agricultural practices mainly involved dry-field farming of grains and millet. Satsumaimo, being a high-calorie crop that thrived even on such poor-quality land, quickly became crucial to supporting the local people’s livelihoods.

The cultivation of satsumaimo, which began in Ryukyu around 1604-1605, subsequently spread via Amami Oshima Island and other islands to southern Kyushu, specifically to the Satsuma domain (present-day Kagoshima Prefecture). There are several historical theories regarding this transmission. One suggests that satsumaimo were brought back by soldiers accompanying Iehisa Shimazu, the lord of Satsuma domain, during the Satsuma invasion of Ryukyu around 1609-1611. Another theory is that in 1698, Hisamoto Tanegashima, the lord of Tanegashima Island, acquired satsumaimo seedlings from Ryukyu King Sho Tei and introduced them to the Satsuma mainland via Tanegashima. A third theory holds that in 1705, a fisherman from Yamagawa in Satsuma Province (present-day Yamagawa, Ibusuki City, Kagoshima), Riemon Maeda, brought satsumaimo seedlings from Ryukyu, cultivated them in his fields, and spread them throughout the surrounding areas. Interestingly, Riemon Maeda was honored for this contribution by being called kansho-o (甘藷翁), the Satsumaimo Elder, and even has a shrine dedicated to him—Tokko Shrine—in Yamagawa, Ibusuki City. Japan thus uniquely has a deity for satsumaimo, complete with a dedicated shrine.

By the early 18th century, satsumaimo cultivation was widely established in the Satsuma domain, valued highly for its ability to grow even in poor-quality soil. In fact, the Japanese term satsuma-imo literally means the potato of Satsuma. Satsumaimo have a high degree of environmental adaptability and initially spread rapidly across Ryukyu and western Japan due to their adaptation to hot, humid climates. Moreover, since satsumaimo could be grown even in nutrient-poor soils or steeply sloping land, they became especially prized in regions like Satsuma, characterized by volcanic ash soils (Shirasu plateaus).

Interestingly, satsumaimo, originally sensitive to cold weather, gradually began spreading to eastern Japan’s colder regions once techniques were developed to store satsumaimo through winter without spoilage and successfully sprout them the following spring. Throughout the Edo period, the expansion of satsumaimo cultivation northward beyond the Kanto region was slow, mainly due to difficulties in cold-weather storage and seedling production. Nevertheless, farmers continually experimented and devised methods such as underground storage cellars called muro or placing straw mats to ensure satsumaimo survived winter.

But why was it necessary to cultivate tropical-origin satsumaimo even in the colder regions of eastern Japan in the first place? During the Edo period, strict regulations prevented crops from being freely transported out of the Satsuma domain, making widespread distribution politically challenging. Under such conditions, it might seem unreasonable to push satsumaimo cultivation all the way to eastern Japan. Yet, there was a profound reason behind this—the repeated famines during the Edo period. Three particularly severe famines occurred from the 18th to 19th centuries: the Kyoho famine of 1732, the Tenmei famine of 1782-1787, and the Tempo famine of 1833-1839. Beyond these, countless other famines also occurred, seriously weakening the Edo government’s rule and ultimately becoming a critical factor leading to the Meiji Restoration.

During these three major famines, mass starvation occurred across Japan, causing devastating losses especially in remote northern areas like Tohoku. Yet remarkably, it was said that the Satsuma domain experienced no deaths by starvation during these crises. The reason lay precisely in satsumaimo, which had already been successfully cultivated there. This knowledge gradually spread to influential leaders in other domains, and satsumaimo began to be seen as a valuable crop for famine relief.

Indeed, story of satsumaimo being the savior during famines eventually moved the Edo government itself. The eighth Tokugawa shogun, Yoshimune Tokugawa (reigned 1716–1745), facing the severe Kyoho famine, turned his attention to satsumaimo as an alternative crop to rice after hearing about their success in Satsuma. The Confucian scholar Kon’yo Aoki (1689–1769), who had learned about satsumaimo through books he encountered in Kyoto, understood their value. Under Yoshimune’s orders, Aoki conducted experimental cultivation of satsumaimo around Edo. In 1735, he succeeded in cultivating satsumaimo in Edo for the first time, using seedlings imported from Satsuma. Kon’yo Aoki documented cultivation methods and submitted a report to Yoshimune, which led to satsumaimo cultivation becoming a government-endorsed project.

Considering famine as one of the greatest threats to the regime, in 1744, the Edo government issued nationwide directives encouraging satsumaimo cultivation, which then gradually took hold around Edo and spread to parts of Kanto and southern Tohoku. Because the seedlings introduced by Kon’yo Aoki originated from Satsuma, this new crop became widely known as satsuma-imo.

However, although satsumaimo could eventually be cultivated as far north as the Kanto region, they did not spread widely throughout all of Tohoku. Most cultivation remained vigorous primarily in Satsuma. Since Tohoku had historically suffered the most severe famine damage, its people gradually developed their own independent famine countermeasures, utilizing insights inspired by famed Sengoku-era warlords. This knowledge-gathering effort began right after the devastating Tenmei famine, with domain lords spearheading large-scale surveys and preparations for future famines. Interestingly, the accumulated wisdom from this period was later actively applied not only during Edo-era famines but even during World War II, helping ordinary citizens survive severe wartime hardships.

As we reflect upon satsumaimo and their role in famine prevention, perhaps modern humanity, now forced to survive in an increasingly degraded global environment, is entering an era of survival challenges equal to or even greater than those famines. Perhaps everyone today needs to start preparing for extreme survival situations before the worst truly happens. Looking at the history of just one crop—satsumaimo—in Japan, I can’t help but feel uneasy about the future. This sense of unease seems increasingly real given Japan’s recent severe rice shortages and price hikes.

For several years now, as I’ve traveled across Japan, I’ve been engaged in the unusual practice of recommending to acquaintances I’ve met on these journeys to start growing satsumaimo, considering historical precedents. Given the accelerating rice crisis, attention toward the Edo period’s famine responses is likely to grow again.

Will Japan’s future continue to be shaken by rice-related issues? Perhaps the collapse of a system centered on rice cultivation symbolizes the collapse of various Japanese values, as I’ve repeatedly discussed here on Shitsurae.