Since the outbreak of the COVID-19 virus, research into potential prevention and cures for this seemingly intractable disease has become an urgent global priority. Given the ‘abnormal’ behaviour of the COVID-19 virus, it is apparent that conventional medical solutions may have limited capacity to control the disease. So, the question is whether our diet may offer alternatives in curbing the spread and alleviating the symptoms of COVID-19 infection.
As with many long-lived cultures, the history of Japan could well be described as one of an ongoing battle with epidemics. The Tenpyō smallpox epidemic of the 8th century wiped out one-third of the nation’s population at the time. As the imperial capital of Kyōto enjoyed its glory days between the 9th to 12th centuries, the nation was repeatedly ravaged by epidemics, famines, earthquakes, volcanic eruptions and weather calamities—which finally led to Japan spiralling into the warlike world of the samurais between the 13th and 16th centuries. Epidemics and natural disasters continued to shape Japanese history until relatively recent times, including a cholera epidemic in Edo (modern-day Tōkyō) in 1858, to which a quarter of the city’s one million inhabitants succumbed.
Curiously though, these epidemics and calamities also contributed to the blossoming of Japanese culture as we know today. World-renowned cultural heritage such as the Tōdaiji temple in Nara (housing the Great Buddha statue), the Byōdō-in temple in Uji (featured on the reverse side of the Japanese 10-yen coin), the Gion Festival of Kyōto, and the Sumida River Fireworks Festival of Tōkyō all originated out of people’s wish for the suffering to end. The Japanese tea ceremony and garden traditions evolved, in part, as a form of diversion from the uncertain everyday life during the ‘Warring’ period of the 15th and 16th centuries when disease—apart from warfare, natural disasters and famines—was rife (see my June 2020 article on Japanese tea gardens https://www.deeplyregionaljapan.com/post/japanese-roji-a-garden-path-to-your-mind-and-spirit-part-1).
Epidemics also influenced Japanese architecture. ‘Shinden-zukuri’, an architectural style for aristocratic residences that developed around the 10th century (Byōdō-in temple mentioned above is a fine example), features a number of ingenious designs aimed at curbing the spread of infectious diseases. The residences consisted of a collection of buildings separated by open corridors and courtyards to ensure adequate ventilation in every part. Inside, layers of removable screens and partitions divided the buildings into sections and rooms, and there were multiple step-ups in floor levels—with the uppermost floor level in the innermost part of the building being reserved for those with the highest social status, while all others were restricted to the lower and outer parts of the buildings.
The overall effect of the ‘shinden-zukuri’ design was to reduce the risk of disease being transmitted through the air, particularly from those of lower social status—who were more likely to be carriers of disease. The rooms forming the living quarters of the nobility were quite small, so as to limit the number of people in each room and to physically distance members of the household across multiple rooms—as an additional precautionary measure. (Sounds all too familiar today in our ‘COVID-19 world’, doesn’t it?)
For a short educational video clip (in Japanese) by Japan’s national broadcaster NHK showing a model of ‘shinden-zukuri’ architecture, visit https://www2.nhk.or.jp/school/movie/clip.cgi?das_id=D0005403019_00000.
Looking through historical records, it becomes apparent that the Japanese over the centuries also recognised the importance of diet in overcoming disease, in a similar vein to the ancient tradition of food therapy in Chinese medicine. Many texts have been written on specific foods for preventing and treating a range of diseases, and the knowledge was disseminated to the general public in some novel ways such as ukiyo-e (woodblock prints) and kabuki theatre.
With the current COVID-19 outbreak, Japan’s remarkably low casualty rate in comparison to most other countries has puzzled the medical profession, especially given that Japan has the highest proportion of aged population in the world, their cities have some of the highest population densities in the world, and the nation did not implement strict lockdown measures. Many theories have been put forward, including Japan’s policy of mandatory BCG (Bacillus Calmette-Guerin) vaccination against tuberculosis, the almost obsessive hygiene habits of the Japanese, or simply the genetic make-up of Japanese people. However, several lines of evidence point toward the Japanese diet as a potentially important factor.
The Japanese diet is unique among all food traditions in the world in the amount and variety of seaweeds used. An interesting insight is provided by how Japan fared comparatively well during the ‘Spanish flu’ outbreaks of 1918–1921 compared to most of the world—with a mortality rate of around 1% compared to the global mean of 3–5%. Even more interesting is the fact that, within Japan, the casualty varied immensely between different regions, with the lowest rates often coinciding with areas with the highest seaweed consumption.
Seaweeds, especially of the brown-coloured varieties such as konbu, wakame and hijiki, are especially rich in fucoidans, a type of carbohydrate. Fucoidans have been scientifically proven to boost immunity, suppress tumour growth, and assist in maintaining circulatory health. Recent research also indicates that fucoidans are effective in preventing the so-called cytokine storm (see https://pubmed.ncbi.nlm.nih.gov/30797011/; https://pubmed.ncbi.nlm.nih.gov/30347679/)—when the body’s immune system ‘goes into overdrive’ in response to, for example, an infection—a major cause of serious complications in both the Spanish flu and COVID-19 outbreaks.
Seaweeds are also high in vitamin K. Some types of nori and wakame in their dry form contain over 1500μg of the vitamin, which has long been known to be essential for bone health and blood clotting. A recent study in the Netherlands (in peer review as at July 2020; see https://www.preprints.org/manuscript/202004.0457/v1) suggests that vitamin K may also assist in alleviating the effects of COVID-19 infection.
The traditional Japanese diet is particularly rich in high-vitamin K foods other than seaweeds, including nattō—the fermented soybeans with their distinct texture and odour, which many non-Japanese find challenging—which typically contains over double the amount of vitamin K compared to cooked leafy green vegetables that many in the Western world regard as a good dietary source (see https://www.medicalnewstoday.com/articles/321586#foods-high-in-vitamin-k). Interestingly, the current COVID-19 outbreak has had relatively low impact on the Tōhoku region of northern Japan, despite the area having the highest proportion of the aged in the nation—an area also with a particularly high per-head consumption of nattō.
Nattō is one of the many vegetable-based fermented foods in the traditional Japanese diet. In fact, the Japanese are among the largest consumers of fermented foods in the world, including miso and tsukemono (pickles)—which continue to be daily staples for the Japanese today. Fermented foods have recently become something of a craze in the modern Western world for their importance in maintaining good gut health—now widely recognised as crucial to (among many other things) a functional immune system. There are indications that, in Europe, those countries with the highest average consumption of fermented vegetable foods had a lower mortality rate during the 2020 COVID-19 outbreak (see https://www.medrxiv.org/content/10.1101/2020.07.06.20147025v1). Whether fermented foods have contributed to the very low COVID-19 casualty rates in Japan remains to be proven.
The Japanese consume the largest amount of green tea per head in the world. Many would already be aware that green tea is a powerhouse of nutrition with an astounding array of health benefits. Perhaps less well known is the fact that green tea has powerful antiseptic properties thank to its high content of catechins—of which, epigallocatechin gallate (EGCG) has been suggested by a recent study (in review as at July 2020) as potentially effective for preventing and treating COVID-19 infection (see https://www.researchsquare.com/article/rs-19560/v1). Given that it is also very high in vitamin C, vitamin K and a number of other immunity-boosting nutrients, green tea may very well hold a key to why the Japanese seem to have survived the current COVID-19 outbreak better than most nations.
The Japanese not only drink copious amounts of green tea, but they also use powdered green tea (matcha) in food, e.g. in sweets and desserts, and in matcha salt (a popular seasoning for tempura). Spent tea leaves are also used as a vegetable in various home-style recipes, a custom more widespread in the frugal olden days. Perhaps it is an accidental stroke of genius, considering most of the original nutrition in tea remains in the spent leaves rather than dissolving into the brew.
There are many other ingredients that the Japanese abundantly use that are not widely found in other food traditions. For example, shiso (perilla; Perilla frutescens var. crispa) is used in several Asian cuisines including Vietnamese (where it is called tía tô) and Korean, but are most widely used in Japanese cuisine—many travelling in Japan would have come across the intensely salty-sour ‘umeboshi’ (pickled plums), whose dark red colour is derived from red shiso leaves. Perilla leaves and seeds have wide-ranging nutritional and medicinal benefits as impressive as those of green tea, and are particularly abundant in vitamins including the previously mentioned vitamin K.
Another herb is yomogi (mugwort; various species of Artemisia), which can be found across a wide area of Asia. In traditional Eastern medicine, it is regarded as an all-rounder in the range of conditions it can potentially treat, however, only in Japanese and Korean cuisines is it also used widely as food—a vegetable as well as in confectionery, e.g. the green mochi filled with adzuki bean paste, with the mochi’s colour derived from cooked yomogi leaves. Yomogi is also the dried herb (moxa) used in the traditional Chinese therapy of moxibustion, popular around the world as an alternative treatment for a range of ailments. During the initial COVID-19 outbreak in China, there were anecdotal reports that moxa sticks assisted in the recovery of patients suffering severe pneumonia. Scientific studies have suggested that extracts from a type of yomogi known as sweet wormwood (Artemisia annua)—a major source of the drug artemisinin used widely in malaria treatment—are effective against both SARS and COVID-19 coronaviruses (see https://www.sciencedirect.com/science/article/pii/S0166354205000690?via%3Dihub and https://www.fu-berlin.de/presse/informationen/fup/2020/fup_20_107-beifuss-corona/index.html).
And how about the fact that an average Japanese eats more octopus and squid than any others in the world—a rich source of zinc and the amino acid taurine—both of which regulate the behaviour of the so-called ACE-2, the entry point for COVID-19 virus into the human body. Or the adzuki beans and soybeans—of which the Japanese are also among the largest consumers in the world—given the abundant polyphenols these beans contain, which numerous laboratory studies have shown to be effective against viral infections. The more I probe, the more I seem to uncover how the traditional Japanese diet (and other healthy traditional food diets around the world) may hold clues to beating the COVID-19 virus through our diet, in combination with other lifestyle habits. My own research science background tells me that no single food substance would completely be effective against COVID-19. However, the combination of a wide variety of ingredients, eaten regularly in small amounts as in the traditional Japanese diet (as opposed to some of the modern Japanese habits…), is undoubtedly the key to boosting your immune system and warding off infections. Dietary ‘fads’ of modern times, when certain substances are cherry-picked for their health benefits and consumed en masse—or taken as dietary supplements—are simply not the same.
I have uploaded to our recipes webpage a few Japanese recipes for you to try at home using some of the ingredients mentioned in this article: https://www.deeplyregionaljapan.com/recipes. More recipes will be added to the list over time, so be sure to check in regularly.
Armed with wisdom from time-honoured food traditions as well as cutting edge modern science, let’s hope that we can eventually ‘eat our way out’ of the COVID-19 crisis…
DISCLAIMER: Information contained in this article does not constitute an advice, recommendation or endorsement for the prevention and treatment of COVID-19 coronavirus infection or any other medical, health and dietary issues. This article does not claim that any specific food substance or product is effective against the COVID-19 virus or any other medical, health and dietary issues. You should always seek professional advice before commencing food-based treatment of any medical, health or dietary issues. Deeply Regional Japan and the author Takehiko Hashimoto disclaim responsibility for any loss, damage or other issues arising from your use of any information contained in this article.