🌡️ Introduction: Body Temperature Regulation – The Body's Rhythm of Life
Our bodies possess a remarkable ability to maintain a stable internal state amidst a constantly changing environment. Just as we feel hunger when empty or seek rest when tired.
Body temperature is part of this vital balance (Homeostasis). If we get too hot or too cold, various bodily functions can't perform at their best.
Fortunately, our bodies are equipped with sophisticated mechanisms to keep our temperature within the "just right" range. Generating heat when it's cold, and releasing heat when it's hot. The smooth functioning of this temperature regulation system is fundamental to our daily well-being.
🔬 A Bit More Technical...
Among the body's homeostatic functions, thermoregulation is essential for sustaining life. The hypothalamus in the brain acts as the primary sensor, coordinating with the autonomic nervous system, endocrine system (hormones), and immune system to control body temperature. Generally, a body temperature around 36.5°C to 37°C (97.7°F to 98.6°F) is considered ideal for the efficient functioning of bodily enzymes and the active response of immune cells.
Conversely, prolonged low body temperature or poor temperature regulation has been pointed out as potentially leading to issues like poor circulation, reduced basal metabolism, and impaired immune function. Supporting this "ability to maintain appropriate body temperature" is crucial for maintaining good health.
🧬 Chapter 1: The Link Between Body Temperature and Your "Defenses"
Our bodies have a reliable defense mechanism called the "immune system" to protect us from external invaders like viruses and bacteria.
This immune system is actually significantly influenced by body temperature. It's known that when body temperature is low, the activity of immune cells can become sluggish.
Conversely, when body temperature is appropriately maintained, or when a fever occurs during infection, immune cells tend to work more actively, boosting our defenses.
The traditional saying "Chilliness is the source of a myriad of diseases" is thought to be related to this deep connection with immune function.
🔬 A Bit More Technical...
Fever during infection is not just an unpleasant symptom but an important biological defense response to activate the immune system. Many studies have shown that an increase in body temperature enhances the functions of immune cells (like T cells, B cells, NK cells, macrophages), including their proliferation, migration, and ability to engulf foreign substances. It's also thought to promote the production of heat shock proteins (HSPs), contributing to cell protection and immune response regulation.
(Reference: Evans SS et al., Nature Rev Immunol, 2015)
Furthermore, lifestyle habits that gently raise body temperature, such as bathing or exercise, are gaining attention for their potential to support these immune functions.
🔥 Chapter 2: How the Body Generates Heat & Hints from Diet
Our bodies have the ability to generate heat internally when needed. This is called "thermogenesis." Shivering in the cold is a clear example of muscles working to produce heat.
However, there's also a mechanism for generating heat without shivering. A key player here is "Brown Adipose Tissue (BAT)." Located mainly around the neck and shoulder blades, BAT has the function of burning some of the energy obtained from food to convert it into heat.
Certain food components are known to potentially support this thermogenesis.
For example, capsaicin found in chili peppers and catechins found in tea have been studied. It's also important to adequately consume nutrients necessary for temperature regulation and metabolism (such as iron).
🔬 A Bit More Technical...
Human thermogenesis includes shivering and non-shivering thermogenesis. The latter primarily relies on the activity of UCP1 (Uncoupling Protein 1) in Brown Adipose Tissue (BAT) and the more recently identified beige adipocytes. UCP1 allows energy from the mitochondrial proton gradient to be released as heat instead of being used for ATP synthesis.
Capsaicin is studied for its potential to activate BAT and increase thermogenesis by stimulating the sympathetic nervous system via TRPV1 receptors. Iron is essential for the synthesis of thyroid hormones, which regulate overall metabolic rate and thermogenesis. Therefore, iron deficiency can lead to impaired ability to maintain body temperature.
(References: Beard JL et al., Am J Clin Nutr, 1990 / Soliman A et al., Acta Bio Medica, 2021 / Hursel R & Westerterp-Plantenga MS, Int J Obes, 2010)
🦠 Chapter 3: Is There a Link Between Gut Health and Body Warmth?
While the gut is primarily known for digestion and absorption, it's actually deeply interconnected with overall health.
When the gut environment is well-maintained, nutrient absorption efficiency improves, supporting smooth energy production in the body. The gut is also a cornerstone of immune function and is closely linked to the autonomic nervous system.
A healthy gut environment is thought to help maintain circulatory and metabolic balance, which in turn contributes to preserving the body's inherent warmth.
Fermented foods are known to support this gut environment. Microorganisms (probiotics) contained in foods like yogurt, natto, miso, and nukazuke, along with the various substances they produce, are expected to help balance the gut flora and support well-being from the inside out.
🔬 A Bit More Technical...
Recent research suggests that the gut microbiota can influence the host's energy metabolism, immune response, and even thermoregulation. For instance, studies in mice have reported that the gut microbiota is involved in the activation of brown adipose tissue and thermogenesis in cold environments (Chevalier C et al., Cell, 2015).
Fermented foods contribute to maintaining gut environmental balance by supplying probiotics (live beneficial bacteria), prebiotics (food for beneficial bacteria), and biogenics (bacterial components and fermentation metabolites). A healthy gut environment may indirectly support overall homeostasis (including temperature regulation) through improved nutrient utilization efficiency, maintenance of the gut barrier function, and appropriate immune and nervous system responses.
(Reference: Marco ML et al., Curr Opin Biotechnol, 2017)
🛀 Chapter 4: Daily 'Onkatsu' Hints: Habits for Comfortably Warming Your Body
"Onkatsu" doesn't have to be complicated. You can start by incorporating small changes into your daily life.
- Bathing: Soak slowly in lukewarm water (around 40°C / 104°F). Also promotes relaxation.
- Keeping Warm: Pay attention to keeping areas like the neck, wrists, and ankles warm.
- Meals: Be mindful of consuming warm foods and drinks. (Note: While this doesn't significantly raise overall body temperature, it can help warm the internal organs and is expected to have a relaxing effect.) Making breakfast a habit is also important.
- Exercise: Promote circulation with light activities like walking or stretching.
- Rest: Aim for quality sleep to help balance the autonomic nervous system.
These habits help promote circulation, balance the autonomic nervous system, and support the body's natural temperature regulation functions.
Find what works for you and cultivate habits that warm your body comfortably without overdoing it.
🔬 A Bit More Technical...
Mild heat stimulation (like bathing) dilates peripheral blood vessels, improving blood flow, and promotes relaxation by making the parasympathetic nervous system dominant. Research also suggests potential cell-protective and immune-modulating effects through mechanisms like the induction of heat shock proteins (HSPs).
Light exercise not only generates heat from muscle activity and improves circulation but also contributes to overall metabolic activation, such as maintaining muscle mass and improving insulin sensitivity when done consistently.
Warm food and drinks, while having a limited sustained impact on core body temperature due to thermoregulation, may temporarily warm the digestive tract, potentially supporting digestive enzyme activity or local blood flow. It also helps avoid rapid temperature drops in the internal organs caused by cold items. Furthermore, the perceived warmth and psychological relaxation effect (influencing the parasympathetic nervous system) from consuming warm items can be beneficial, making moderate intake recommended within a comfortable range.
🌼 Conclusion: Small Daily Habits Become Seeds of Well-being
"Onkatsu" isn't just about physically warming the body.
It's a process of recognizing and gently nurturing the body's inherent ability to maintain its own well-being.
Taking time for a slow bath. Enjoying a warm drink for a moment of calm. The comfort of moving your body with light exercise.
And incorporating the bounty of nature into your daily meals.
In particular, fermented foods are traditional foods that support daily well-being by nurturing the gut environment – the foundation of the body. Incorporating diverse fermented foods like yogurt, miso, natto, or nukazuke into your diet can help balance gut flora, aid nutrient absorption, and potentially support immune function and metabolism.
This, in turn, can be said to contribute to building the foundation for maintaining the body's inherent "warmth."
Find ways to care for your body comfortably, at your own pace.
📚Source & References
- Evans SS, Repasky EA, Fisher DT. (2015). Fever and the thermal regulation of immunity: the immune system feels the heat. Nature Reviews Immunology, 15(6), 335–349.
https://doi.org/10.1038/nri3843 - Ludy MJ, Moore GE, Mattes RD. (2012). The effects of capsaicin and capsiate on energy balance: critical review and meta-analyses of studies in humans. Chemical Senses, 37(2), 103–121.
https://doi.org/10.1093/chemse/bjr100 - Chevalier C, et al. (2015). Gut microbiota orchestrates energy homeostasis during cold. Cell, 163(6), 1360–1374.
https://doi.org/10.1016/j.cell.2015.11.004 - Marco ML, et al. (2017). Health benefits of fermented foods: microbiota and beyond. Current Opinion in Biotechnology, 44, 94–102.
https://doi.org/10.1016/j.copbio.2016.11.010 - Soliman AT, et al. (2021). Iron deficiency anemia and thyroid function. Acta Bio Medica, 92(4), e2021285.
https://doi.org/10.23750/abm.v92i4.11617 - Hursel R, Westerterp-Plantenga MS. (2010). Thermogenic ingredients and body weight regulation. International Journal of Obesity, 34(4), 659–669.
https://doi.org/10.1038/ijo.2009.299 - Saito M. (2015). Brown adipose tissue as a target for preventing and treating obesity-related metabolic diseases. Endocrine Journal, 62(8), 679–689.
https://doi.org/10.1507/endocrj.EJ15-0294 - Beard JL, Borel MJ, Derr J. (1990). Impaired thermoregulation and thyroid function in iron-deficiency anemia. The American Journal of Clinical Nutrition, 52(5), 813–819.
https://doi.org/10.1093/ajcn/52.5.813
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