Naoyuki Hayashi - What is "health"? – A unique look at exercise and nutrition

"According to the World Health Organization, health is a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity," Hayashi explains. "It was not until the Edo-era (1602-1868) that the term "kenkou" (health) began to be used in Japan, established by scholar Koan Ogata. In Ogata's time, the connection between exercise and health was unknown among the Japanese. In the Meiji Period (1868-1912), Japanese author and educator Yukichi Fukuzawa introduced the general public to the idea that exercise is healthy. Awareness of health strongly depends on one's sense of value. For this reason, it is important to have an environment that allows us to understand and freely choose ways to improve our health. My role is to help create this environment through science."

Exercise, nutrition, and rest are three major factors in health. Drawing on his experience as an athlete, Hayashi focuses his research on exercise and nutrition.

Facial blood flow changes in a subject who felt that consommé tasted good. Red areas indicate high blood flow, and blue areas indicate low blood flow. After tasting the consommé, blood flood in the eyelids increased. (Palatability of tastes is associated with facial circulatory responses, Chemical Senses)

Nutritious, good-tasting food is important to maintaining a healthy diet. When we like the food we eat, we feel happy and our facial expressions change. While facial expressions are hard to quantify, Hayashi attempted to measure facial blood flow using laser speckle flowgraphy.

"We measured changes in facial expressions when people ate things they felt tasted good and tasted bad. A study of 15 subjects showed that blood flow in the eyelids increased when they ate something that tasted good, and decreased when they ate something that tasted bad."

When the subject did not like the taste, blood flow in the nose decreased, which is consistent with studies on animals. When animals fight, they often receive bites on the nose, which can bleed. Blood flow also decreases in animals when they feel discomfort or perceive risk. It is natural, therefore, to assume that blood flow in the human nose decreases in response to something that tastes bad. However, the discovery that blood flow in the eyelids increases when tasting something good was new and unexpected.

"Because changes in blood flow in the eyelids are not externally observable, they likely do not function as a means of communication like our cheeks when we blush. Although blood flow in other parts of the body is controlled by the sympathetic nerve system, blood flow in the face is thought to be controlled by both the sympathetic and parasympathetic nerve systems. While it is not yet understood why eating something that tastes good increases blood flow, this discovery could allow us to use changes in blood flow to determine how patients who have difficulty communicating feel about the taste of food. This would make it possible for hospitals to provide food that better suits such patients' tastes," says Hayashi.

Hayashi began his research on health when he entered the Department of Sports Sciences at Waseda University. "Since my elementary school days, I've enjoyed science and swimming. That's why I chose this school. I was interested in knowing why athletes' heart rates are lower. I wanted to explore those mechanisms."

He then started investigating blood flow changes in the face and organs using laser speckle flowgraphy, which led him to his current research. Hayashi explains, "Facial blood flow is still largely a mystery. The more I study, the deeper my interest becomes."

Currently, Hayashi's team seems to be the only group working on these topics. Despite this, he hopes to clarify the mysteries of blood flow and identify factors that help maintain and improve health.

"Although exercise makes us healthier, not everyone's lifestyle involves a lot of movement. From what I have found, Kabuki actors, tea masters, rakugoka (traditional Japanese comic storytellers), and nagauta (classical singers) generally live long. However, with the exception of Kabuki actors, there is not a great deal of vigorous physical activity in these traditional Japanese arts. In other words, there must be factors related to maintaining health other than exercise, nutrition, and rest. I would like to identify those other factors."

When asked what advice he has for young researchers, Hayashi states, "It is important to study what you are interested in, because what you like, you will do well. If you want to be a researcher, however, it is also important to be familiar with as many areas as possible. Narrowing your area of expertise prevents you from increasing the depth and breadth of your research. Because global trends change quickly, others may be involved in research similar to what you are engaged in. You need to be strong and flexible enough to allow your goals and perspectives to evolve and continue finding new areas that interest you."