[Kim Jaeho's Life Story]<217> The Health Protected by My Body's Ecosystem

All living organisms live together as a community with other living organisms around them, and this community is called an ecosystem. Living organisms survive by interacting with other living organisms as well as non-living substances such as soil, air, and water that surround them within the ecosystem. Ecosystems can be as small as a pond or a forest, or as large as the entire Earth, and the human body itself is also an ecosystem.

It is known that the human ecosystem hosts more than 100 trillion microorganisms such as bacteria, viruses, and fungi, which outnumber human cells by ten times. According to one study, the weight of microorganisms living in the human ecosystem ranges from 0.9 kg to 2.7 kg for an adult weighing 90 kg. These microorganisms form small ecosystems in the gastrointestinal tract, skin, mouth, lungs, reproductive organs, the uterus and breast milk of mothers, liver, eyes, and nose. Some biologists say that including the fetus, no tissue in the human body is sterile.

People maintain close and complex relationships with the microorganisms living with them, and humans and microorganisms greatly influence each other's lives. For microorganisms to survive, they need the human ecosystem environment provided by people. Since lifestyles, diets, use of antibiotics or medicines, and living environments differ from person to person, the human ecosystem varies among individuals.

The relationships between microorganisms living in the human ecosystem and humans can be divided into three types. First is a symbiotic relationship where both benefit; second is a relationship where one benefits while the other is unaffected; and third is where one benefits but the other is harmed. Most microorganisms living in the human ecosystem are known to be either symbiotic or harmless.

Microorganisms in the human ecosystem play very important roles in our lives. They break down dietary fiber to produce short-chain fatty acids, prevent the invasion of disease-causing bacteria, synthesize essential nutrients and vitamins, and are related to a wide range of conditions from gut health to obesity, arthritis, and Alzheimer's disease. Gut microorganisms help immune cells control infections and assist the central nervous system that regulates brain functions.

Scientists believe there is a close relationship between the diversity and balance of microorganisms living in the human ecosystem and our susceptibility to diseases, and that the diversity and balance of microorganisms are important for our health. The diversity and balance of microorganisms are also necessary for strong immunity.

Some scientists think that babies who have little contact with these microorganisms suffer more severe symptoms of allergies, asthma, and eczema, and some research suggests that microorganisms play a significant role in obesity and depression. Microorganisms in the human ecosystem are so important that they function like an organ or tissue such as skin or kidneys.

Although it is not yet fully understood how microorganisms in the human ecosystem affect our health and diseases, it is continuously confirmed that the diversity and balance of these microorganisms greatly help maintain our health. The large intestine hosts the most bacteria, which control digestion, the immune system, and the central nervous system, and when this balance is disrupted, obesity increases.

Some bacteria contribute to inflammation and tissue destruction in the mouth, while others contribute to health beyond the gums, tongue, and teeth. When the balance of these microorganisms is disturbed, harmful bacteria increase and cause diseases in the mouth. The bacteria living in the lungs are far fewer in number compared to the large intestine but show considerable diversity. When the bacterial balance is disrupted, the lungs’ innate immunity is impaired, which can worsen chronic lung diseases.

The skin ecosystem hosts about 1,000 types of microorganisms, most of which live in symbiosis with the skin and provide various benefits. When the balance among microorganisms is disturbed, harmful bacteria can easily infect the skin, causing or worsening various skin diseases (see Life Story episode 184). We often see such examples around us.

As research on the human ecosystem increases, it is steadily confirmed that the best doctor to protect my body’s health is the symbiotic relationship with the microorganisms living in my body’s ecosystem. Therefore, if we always remember and practice that creating a good environment for the microorganisms living in my body’s ecosystem is the best way to protect my health, won’t my body’s ecosystem reward me with health?

Kim Jaeho, Love and Life