Social interest in sleep has increased due to the 24-hour nature of society and the aging population. Chronic sleep disturbance is known to increase the risk of developing mental disorders such as depression and lifestyle-related diseases such as diabetes, and sleep disorders are considered to represent mental, physical, and economic social problems. We have developed a mouse model that can be extrapolated to human sleep disorders, with the aim of clarifying the mechanisms of sleep disorders and the onset of diseases related to them, developing non-invasive biomarkers for early detection of chronic sleep disturbance, and finding foods that can help to improve sleep. In this model, water is placed at the bottom of a cage in which a mouse remains on an unstable running wheel. This mouse model is able to explore aspects such as disruption of circadian rhythms of wheel-running activity and sleep-wake cycles, hyperphagia due to reduced secretion of leptin, impairment of glucose tolerance, increased anxiety, and decreased cognitive function. In this paper, we introduce the development of sleep-improving foods using this model mouse, sex differences in sleep disturbance, and the development of a non-invasive biomarker using saliva to evaluate chronic sleep disturbance.

Peripheral tissues, including the liver, transmit an individual's current metabolic status to the central nervous system via neural or vascular pathways. Therefore, it is possible that the biological clock of peripheral tissues responding to feeding rhythms may affect brain function, including energy metabolism regulation. In addition, feeding rhythms may affect brain function and transgenerational effects. On the other hand, it has been suggested that the timing of meals after an event may affect brain function to a greater degree than the feeding rhythm. In this study, we overview the physiological mechanisms by which the rhythm and timing of nutritional intake affect brain-mediated phenotypes, such as the central metabolic regulatory system and emotional behavior, along with our own results. In the future, it will be necessary to clarify whether such changes in the central nervous system are physiologically essential for homeostasis, or are merely secondary effects. In addition, we expect that the concept of “chrononutrition” will lead to a better understanding of aspects such as meal timing and transgenerational effects.

Breakfast skipping has become a social issue in Japan, as it is reported to increase the risk of obesity, diabetes, and cardiovascular disease. Although breakfast is an important factor for regulation of the circadian rhythm, and the National Health and Nutrition Survey in 2019 found that the average energy intake at breakfast accounts for 21.1％ of the daily total, the overall rate of breakfast skipping was 12.1％, the rate being as high as 21.5％ for young adults in their 20s and 30s and 4.6％ for children, which means that the respective targets of 15％ and 0％ have yet to be achieved. The average energy intake in the form of snacks per day has been calculated to be 7.3％ for men and 8.7％ for women on the basis of Japanese dietary records, and it has been reported that snacks contribute to nutritional supplementation not only in the young but also in the elderly. However, few studies have examined the timing and amount of individual snack foods. We have been studying the optimal timing for intake of granola and specific snack products such as potato chips. We anticipate that this approach will contribute to increased recognition and understanding of chrono-nutrition and its impact on society.

Nutrition plays an important role in maintaining the health of older adults. Chrono-nutrition is a concept that aims to prevent disease and prolong healthy life expectancy through a dietary habit that takes into account the biological clock. As the human circadian rhythm is longer than the 24-hour cycle of the Earth, it needs to be converted to a daily day and night cycle. Diet affects circadian rhythms, and maintenance of adequate muscle strength in older adults is important for delaying the start of long-term care. In recent years, it has been shown that genes associated with the skeletal muscle clock control muscle function and that muscle protein synthesis is enhanced when a large amount of protein is consumed, especially at breakfast. However, it is sometimes difficult for older people to consume enough protein because dietary intake decreases with age. In a longitudinal study, by focusing on protein quality (i.e., bioavailability), we have found that community-dwelling older people who eat a high-protein-quality breakfast are less likely to develop muscle weakness. Despite a lack of evidence on recommended nutrient intakes for older people, here we consider the nutritional management of older adults from a chrono-nutritional perspective.