Lukewarm Water: What Is It Helpful In And Why?

Lukewarm water — aqua tepida in Latin — sits at a moderate temperature, roughly midway between cold and hot. In traditional systems such as Ayurveda and Traditional Chinese Medicine (TCM), it has long been favoured as a drinking and hydrotherapy temperature, on the reasoning that it sits close to the body’s own internal temperature and is gentler on digestion than very cold or very hot water.

Modern research on water temperature and human physiology is comparatively young and, in several areas, mixed. This article sets out what lukewarm water is, how traditional systems frame its use, and what some available research provides further insight into— internally as a drink and externally in hydrotherapy.

Key Points

• Lukewarm water generally refers to roughly 36–40.5°C (98–105°F) — close to core body temperature.
• Ayurveda and TCM both favour warm or room-temperature water for drinking, framed through concepts such as Agni (digestive fire) and the balance of the doshas.
• Modern day research on drinking temperature and digestion or metabolism is often based on small samples, and findings are mixed rather than conclusive.
• Warm water immersion (hydrotherapy/bathing) has somewhat more established research behind it than drinking temperature, particularly for circulation and relaxation.

What Counts as “Lukewarm”?

Lukewarm water is typically described as falling between roughly 36–40.5°C (98–105°F), while room-temperature water is usually placed closer to 22–25°C. Where exactly the line falls depends on context — bathing, drinking, or hydrotherapy each have slightly different conventions — but the common thread is water that is comfortably warm rather than hot or cold.

For reference, normal human core body temperature sits at around 37°C (98.6°F), with a healthy range generally cited as roughly 36.5–37.5°C. Gut and stomach temperature tracks closely with core temperature, though it dips briefly when a cold drink is taken before returning to baseline.

The pH of Water

Pure water at 25°C has a pH of approximately 7 — neutral on the 0–14 scale — with values below 7 indicating acidity and above 7 indicating alkalinity. Water’s pH can shift slightly depending on its source, treatment, and exposure to air, but the underlying chemistry of temperature and neutrality is well established.

Traditional Perspectives: Ayurveda and TCM

In the Ayurvedic tradition, water temperature is considered relevant to digestion and to the balance of the doshas. Warm water is generally held to support Agni, the digestive fire, and is traditionally recommended as more balancing for Vata (associated with dryness and irregularity) and Kapha (associated with heaviness and sluggishness), while cooler water is more often suggested for a Pitta-dominant constitution. Drinking frequent cold water, in this framework, is thought to dampen Agni over time with frequent use (not the occasional drink).

Traditional Chinese Medicine holds a broadly similar view: digestion is likened to a pot that requires warmth, and the Spleen–Stomach system is traditionally thought to function better with warm or room-temperature water, with cold or iced drinks associated with “Cold” or “Damp” patterns such as bloating and sluggish digestion.

These are long-standing theoretical frameworks within their respective systems of traditional medicinal sciences. They are presented here as part of the wider, holistic picture — one that sits alongside, rather than in place of, the mainstream current-day research below. And this is ever-developing.

What Research Suggests: Drinking Lukewarm Water

Metabolism and “Water-Induced Thermogenesis”

A frequently cited small study (Boschmann et al., 2003; 14 participants) found that drinking 500 ml of water at 22°C increased metabolic rate for a period afterwards, with roughly 40% of that increase attributed to the body warming the water to core temperature. This is an interesting early observation, but it has not consistently replicated: a 2006 follow-up (Brown, Dulloo & Montani) found that room-temperature water produced no measurable increase in energy expenditure, and a 2015 reassessment (Charrière et al.) concluded that water ingestion on its own does not appear to meaningfully stimulate thermogenesis or fat oxidation. But other factors such as health status and individual suitability all need to be factored in.

Taken together, the honest position is that any metabolic “boost” from drinking water temperature may be modest and dependent on several individualistic factors.

Digestion and Gastric Emptying

Research on drinking-water temperature and digestion is limited. One human study (Mishima et al., 2009) found that hot meals (around 60°C) sped up the early phase of gastric emptying compared with body-temperature or cold meals — a finding about heat specifically, rather than a general case for lukewarm water over cold.

A separate small study on rehydration after exercise (Hosseinlou, Khamnei & Zamanlu, 2013; six participants) found that cool water, around 16°C, was associated with the best voluntary drinking and rehydration response — the opposite of a “warmer is always better” conclusion. A more recent study (Fujihira et al., 2020; 11 healthy young men) found that cold water (2°C) reduced subsequent energy intake and gastric contraction frequency compared with warmer water, suggesting temperature may influence short-term appetite regulation, though this remains a preliminary, small-sample observation.

Overall, mainstream observations do not seem to support the idea that cold water meaningfully impairs digestion in healthy individuals, nor does it clearly establish lukewarm water as superior for digestion — the picture is more nuanced than either extreme suggests.

What Research Suggests: Warm Water Immersion

Separately from drinking, warm water immersion — bathing or hydrotherapy — has somewhat more developed research behind it. An integrative review (An, Lee & Yi, 2019) covering 13 studies, most in young healthy adults, reported that warm water immersion was associated with improved blood flow, and drew on individual studies suggesting benefits for vascular markers and short-term brain oxygenation with warm-water leg immersion. The review’s authors noted that, because immersion protocols varied considerably across the included studies, the evidence as a whole did not clearly establish conclusively and may vary individual to individual.

Separately, hydrotherapy has traditionally been associated with muscle relaxation and relief from soreness, stiffness and general tension, particularly through the combined effects of warmth and buoyancy — an association with a long history in rehabilitation settings and traditional practice, even where the underlying research base for drinking temperature specifically remains limited, which again does not imply conclusiveness.

Summary

Lukewarm water sits at the intersection of long-standing traditional practice and a still-developing area of modern research. Ayurveda and TCM both frame warm or room-temperature water as more supportive of digestion than cold water, through the lens of Agni, the doshas, and the Spleen–Stomach system respectively.

Modern mainstream research offer a more mixed picture: possible, modest effects on metabolism and gastric emptying that vary by study and have not always replicated, alongside a somewhat firmer evidence base for warm water immersion and circulation. Read together, the traditional and research-informed perspectives point to lukewarm water as a plausible, low-risk choice within a well-rounded routine — rather than in isolation.

Suitability and Precautions

The information presented in this article is subject to individual suitability and individual health status. This is an informational post only and does not constitute professional or medical advice. Seek the advice of a professional.

References in the article can be cross-checked as detailed below. This post is AI-assisted, not AI-generated, and is cross-referenced.

---

References in this article

1. Boschmann, M., Steiniger, J., Hille, U., Tank, J., Adams, F., Sharma, A. M., Klaus, S., Luft, F. C., & Jordan, J. (2003). Water-Induced Thermogenesis. The Journal of Clinical Endocrinology & Metabolism, 88(12), 6015–6019. https://doi.org/10.1210/jc.2003-030780
2. Brown, C. M., Dulloo, A. G., & Montani, J. P. (2006). Water-Induced Thermogenesis Reconsidered: The Effects of Osmolality and Water Temperature on Energy Expenditure after Drinking. The Journal of Clinical Endocrinology & Metabolism, 91(9), 3598–3602. https://doi.org/10.1210/jc.2006-0407
3. Charrière, N., Miles-Chan, J. L., Montani, J. P., & Dulloo, A. G. (2015). Water-induced thermogenesis and fat oxidation: a reassessment. Nutrition & Diabetes, 5(12), e190. https://doi.org/10.1038/nutd.2015.41
4. An, J., Lee, I., & Yi, Y. (2019). The Thermal Effects of Water Immersion on Health Outcomes: An Integrative Review. International Journal of Environmental Research and Public Health, 16(7), 1280. https://doi.org/10.3390/ijerph16071280
5. Mishima, Y., Amano, Y., Takahashi, Y., Mishima, Y., Moriyama, N., Miyake, T., Ishimura, N., & Kinoshita, Y. (2009). Gastric emptying of liquid and solid meals at various temperatures: effect of meal temperature for gastric emptying. Journal of Gastroenterology, 44(5), 412–418. https://doi.org/10.1007/s00535-009-0022-1
6. Hosseinlou, A., Khamnei, S., & Zamanlu, M. (2013). The effect of water temperature and voluntary drinking on the post rehydration sweating. International Journal of Clinical and Experimental Medicine, 6(8), 683–687. https://pmc.ncbi.nlm.nih.gov/articles/PMC3762624/
7. Fujihira, K., Hamada, Y., Yanaoka, T., Yamamoto, R., Suzuki, K., & Miyashita, M. (2020). The effects of water temperature on gastric motility and energy intake in healthy young men. European Journal of Nutrition, 59(1), 103–109. https://pmc.ncbi.nlm.nih.gov/articles/PMC7000532/
8. U.S. Geological Survey. pH and Water. USGS Water Science School. https://www.usgs.gov/water-science-school/science/ph-and-water
9. Physiology, Temperature Regulation. StatPearls, NCBI Bookshelf. https://www.ncbi.nlm.nih.gov/books/NBK507838/