Lessons from the Gut – Microbiome Analysis of Residents from the Hometown of the World’s Oldest Man
Centenarians in the Japanese city of Kyotango, the bluest of the country's "blue zones," enjoy a life expectancy three times the national average.
What’s new: On June 27, 2024, Professor Yuji Naito1 of Kyoto Prefectural University of Medicine (Bioimmunology and Nutrition) presented his preliminary findings during the past 6 years of a planned 20-year research project on the residents of Kyotango City (京丹後市, "Kyotango") at the 27th Annual Meeting of the Society for Bacteriology of the Intestine in Tokyo. This city, located on the Sea of Japan in the northern part of Kyoto Prefecture, is one of the few Japanese areas with an exceptionally long life expectancy - 3 times the national average in the country with the world's longest life expectancies among a large population at just under 85 years. It is one of the bluest of Japan's many "blue zones2.”
"When we started our research here, there were 155 people over 100 years old per 100,000 people. The national average is only 53. Thus, Kyotango's ratio was already three times Japan's quite respectable national average 6 years ago. When I present this kind of data, people often ask, ‘Aren't all of them bedridden?’ No! When the sun rises, they go to the fields, the sea, and the mountains to grow their own food.” - Professor Naito
About a decade ago, the town gained global notoriety as the home of the world's oldest man (at the time), Jiroemon Kimura (木村 次郎右衛門), who died in 2013. He was born in Kyotango on April 19, 1897, and his record of 116 years and 54 days has yet to be broken.
Why it matters: Studies of the microbiome of seniors in Kyotango may hold clues to prolonging life. Kyotango is a relatively small city with less than 20,000 people over the age of 65. Professor Naito's research team asks these people to help them discover the secrets of their longevity by taking blood samples and measuring their walking speed and grip strength. The researchers have focused on the diets of this cohort of elderly Japanese, with a special emphasis on the bacteria in their gut.
The residents of Kyotango not only have a long average life expectancy, but also a healthy and long-lived population with few diseases. Among the 798 people over the age of 65 in the study, Kyotango has a very high percentage of exceptionally healthy people.
Diabetes: Only 1.8% are suspected of having diabetes. This compares to about one in three 65+ year-old residents of Tokyo and a national rate of about one in four elderly people.
Dementia: Only 7.5% are suspected of having dementia, compared to the national average of about 15% for all people over the age of 65.
Decreased Muscle Mass: Only 17.1% have a decreased grip strength measurement that indicates sarcopenia, an aging phenomenon in which muscle mass decreases. The national average for people over 65 is 23.3% for men and 34.1% for women.
Frailty: Only 15% are considered frail, a decline in both physical and mental function due to a decrease in physical ability, cognitive function, and social connectedness. Curiously, national statistics indicate that the proportion of frail Japanese over the age of 65 is about 10%, although the percentage varies somewhat depending on the survey methodology and definition.
Appearance: Although difficult to measure objectively, about 15% of all men appear at least 5 years younger than their actual age.
The bottom line: So far, Professor Naito has concluded the following:
Long Healthy Life Span: Kyotango not only has a high rate of centenarians, but the city also has an unusually high rate of elderly residents who are healthy.
Data to Support Hypothesis: Grip strength, walking speed, and butyrate-producing bacteria have been confirmed as accurate predictors of calendar age.
Link between Frailty and Microbiome Analysis: The subjects' Modified Frailty Index3 scores correlate with certain gut bacteria.
Traditional Japanese Diet: The higher the Japanese diet score, the lower the Frailty Index score and the greater the correlation with gut microflora, especially with respect to the contribution of legumes.
Zoom in: Professor Naito's team focuses on studying which types of people tend to age rapidly. They have identified and confirmed many factors that cause certain elderly people to age faster than their biological age and vice versa.
It turns out that one of the key indicators of those who biologically age quickly is a slow walking speed. The second is weak grip. Muscle strength is very important. Balance, hearing, and vision are also significant. Appearance (without makeup) is a critical factor. In addition, a person's attitude toward aging affects his or her longevity: the more negative a person is about aging, the older he or she tends to be. Professor Naito also emphasized that the tendency to become hard of hearing, if left alone, will gradually cause a person to age prematurely.
"The more information you have, the less you age. By all means, spend money on hearing aids. Just the fact that you have proper information coming in through your ears is enough to prevent dementia.” - Professor Naito
In addition to these somewhat obvious factors, the researchers are tracking how their 798 subjects digest their food.
"Until now, we have always calculated how many calories are in a unit of white rice and other foods and simply recommended an ideal number to consume to our patients." - Professor Naito
He explained that it's not just about what you eat. Professor Naito advocates a "new nutrition science" that focuses on the role of gut bacteria in the process of breaking down and absorbing food in the intestines.
"It is not the colon that controls nutrition and immunity in our bodies. It is the small intestine. When we consume fiber, the fiber suppresses various phenomena that occur in the small intestine, thereby reducing inflammation. My current hypothesis is that the result is the suppression of fatty liver and muscle atrophy.” - Professor Naito
Go deeper: Professor Naito also conducted detailed data analysis of the microorganisms living in the intestines of his 798 subjects and found that three bacteria in particular are useful for predicting age. The most important are short-chain fatty acids, or tansa shibo san (短鎖脂肪酸), and butyrate-producing bacteria, or rakusan sansei kin (酪酸産生菌).
So far, researchers have concluded that a traditional Japanese diet, which routinely includes daily servings of miso soup, seaweed, pickles, green and yellow vegetables, beans, green tea, and unsweetened coffee, may actually be better than the Mediterranean diet for preventing sarcopenia, a loss of muscle mass. The higher the Japanese Diet score, the lower the mortality rate from cardiovascular and heart disease. In addition, the higher the Japanese Diet score, the healthier the gut and the lower the rate of dementia.
What’s next: At this point, you may be asking yourself, "Okay. I get it, but what should I do to live longer by improving my gut?" While studies are ongoing, some rules to live by include the following:
Eat More Fiber: Fiber (e.g. from vegetables such as broccoli, beans, lentils, etc.) feeds intestinal bacteria and increases the number of good bacteria.
Eat Fermented Foods: Fermented foods are rich in beneficial bacteria such as Lactobacillus, Bacillus natto, and tofu.
Limit Red Meat Intake: Ham, especially processed ham such as sausage, should be avoided. Although Professor Naito seems to advocate vegetarianism, he recognizes the importance of fish in the Japanese diet - including the diet of the elderly residents of Kyotango, who live near the Sea of Japan and tend to eat a lot of fish and crustaceans such as crabmeat. Thus, the researchers recommend eating fish much more than red meat.
Eat Oligosaccharides: Oligosaccharides, sometimes called "oligos," are a type of carbohydrate found in many foods made with plants. Certain types of oligosaccharides act as prebiotics, which feed the good bacteria in your gut, promoting a healthy gut microbiome that can benefit overall health and digestion.
Consume Quercetin: Quercetin is a plant pigment known as a flavonoid. It is a major constituent, a polyphenol, of green tea, a very popular beverage in Japan. Professor Naito's researchers are now investigating whether there is any correlation between health and the amount and frequency of green tea drinking in Kyotango.
Exercise: Exercise increases the diversity of intestinal microflora.
Get Enough Sleep: Lack of sleep can lead to a poor intestinal environment.
Commentary: Professor Naito's research also suggests that there is an advantage to living in the countryside of Japan, probably related to the relative ease of obtaining fresh fruits and vegetables, as well as the ability to get some exercise without being consciously aware of moving around all the time, simply by walking up and down hills. The research is music to my ears and helps to confirm our decision to leave the salaryman's lifestyle in central Tokyo and move to a rural part of Kyushu exactly 5 years ago to the day.
While there may be something special about Kyotango that Kyushu does not have, I feel that many parts of the Japanese countryside have a lot in common with this city. While it looks like a great place to live, famous for both seafood and mountain produce, I for one am glad we chose an area of the country that is also famous for hot springs. As noted in "News Flash: Japanese Onsen Hot Springs Are Good for Your Health! A growing body of clinical evidence is being used to prove the positive effects and health benefits of hot springs, called onsen in Japanese," it seems like we made a good choice.
Still, there is much to learn from Professor Naito and his research. I promise to take his dietary advice to heart, although many of the things I love (e.g. steak) are to be avoided - at least in large portions. Curiously, Kyotango is famous for its beef, which is branded as Tango Beef or Tango Gyu (丹後牛). Perhaps the locals simply ship almost all of it to neighboring Kyoto (City) to feed the millions of tourists who are willing to pay a premium for these special cuts of wagyu.
Professor Naito also seems to be an advocate of fecal transplants as a means of rejuvenating the intestines. Fecal transplantation, also known as fecal microbiota transplantation (FMT), is a medical procedure in which stool from a healthy donor is introduced into the intestine of a person with an intestinal disease. It may sound unpleasant, but FMT can be a very effective treatment for certain conditions, such as a recurring infection like Clostridium difficile, which causes severe diarrhea and inflammation in the colon. However, Professor Naito suggests that such transplants may one day be used by healthy, elderly people as a kind of fountain of life.
"When fecal matter from a young rat is transplanted into an old rat, the rat becomes young again. The rat's grip strength is also restored. If we can succeed with rats, we will soon succeed with humans...You might as well get the feces of young, energetic, vegetarian athletes who exercise frequently." - Professor Naito
Ah, yeah…Well, he had me right until I came across this suggestion. For now, I will just stick to high-fiber foods, fish, and green tea, while exercising frequently and always trying to get a good night's sleep. Let's leave FMT to the rats!
Link to Japanese Source: https://www.asahi.com/relife/article/14964604
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Professor Yuji Naito, Graduate School of Medicine, Kyoto Prefectural University of Medicine (Bioimmunology and Nutrition), graduated from Kyoto Prefectural University of Medicine in 1983. He is also a board member of the Japanese Society for Oxidative Stress Research, the Japanese Society of Gastroenterology and Immunology, the Japanese Society of Anti-Aging Medicine, and an advisor to the Osaka Pavilion Promotion Committee for the 2025 Japan International Expo. He specializes in gastroenterology, gastrointestinal endoscopy, anti-aging, and intestinal microflora. He is the author of many books, including Your Gastrointestinal Tract (Tummy) is Crying (「消化管(おなか)は泣いています」) and How to Create a Wise Intestine that Changes Your Life (「人生を変える賢い腸のつくり方」).
A Blue Zone is a region of the world where people live exceptionally long and healthy lives, often exceeding 80 years. These areas are known for having a high concentration of centenarians (people who live to be 100 or older).
The Modified Frailty Index is a tool used to assess an individual's level of frailty. Frailty is a state of reduced resilience to stressors that makes older adults more vulnerable to adverse health outcomes. This assessment helps to estimate a person's risk of complications such as falls, hospitalization, and even death.
Very interesting! Diet and exercise built into traditional rural life in Japan certainly appear important. Another factor, I'm guessing, is the low level of anxiety that comes with living long-term in a small place where people know each other and don't relocate much. Also, no religious stress over being judged after death and perhaps going to hell.
Naito's recommendations had me hooked until the end; what a mic drop moment. Some studies suggest the same about blood—apparently, the ultimate solution to staying healthy seems to always involve leeching off healthier specimens.