9 in 10 People Consciously Replenish Fluids Daily, Yet About 1 in 5 Have Experienced Dehydration. Top Reason for Neglecting Hydration in Cool Indoor Environments: "Don't Feel Thirsty." Beware of "Hidden Dehydration" Without Symptoms!

Premium Water Co., Ltd. (headquartered in Minato-ku, Tokyo; President and CEO: Akinohiko Kanemoto), a provider of premium natural water sourced from one of Japan’s finest spring regions and delivered to homes using non-heated processing to preserve both taste and mineral content, conducted a survey on hydration awareness among its subscribers.

Survey Overview

Target: Premium Water subscribers aged 20s to 60s (total 13,247 people)

Method: Questionnaire survey

Period: May 11 (Mon) – May 17 (Sun), 2026

* Figures in the results are rounded to the nearest whole number or one decimal place; therefore, totals may not add up exactly due to rounding.

* When referencing these results, please credit: "Survey by Premium Water Co., Ltd."

【Survey Summary】

・93.9% of respondents consciously replenish fluids regularly.

Among them, 84.9% remain conscious of hydration even when staying in cool, air-conditioned indoor environments.

・The top reason for not consciously hydrating indoors is "don't feel thirsty" (76.0%), followed by "forget to drink" (29.1%) and "believe the risk of dehydration is lower indoors than outdoors" (10.9%).

・The most common daily fluid intake was "800 mL to less than 1 L" (27.7%). This falls short of the recommended amount for boosting immunity—approximately 1.2–1.3 L for adult men and 1.1 L for women. (Note: Dehydration is known to disrupt gut health and reduce immune function.)

・22.7% of respondents reported having experienced dehydration at some point.

・"Hidden dehydration"—a condition where individuals are dehydrated without noticeable symptoms—is becoming increasingly common. Especially in summer, prolonged exposure to cool, dry, air-conditioned indoor environments can lead to inadequate hydration, increasing the risk of hidden dehydration.

・Dr. Hideki Taniguchi shares signs and prevention strategies for hidden dehydration!

・Among those who consciously hydrate daily, 84.9% also make an effort to drink fluids regularly in cool, air-conditioned rooms. For those who do not, the top reason is "don't feel thirsty" (76.0%), followed by "forget to drink" (29.1%) and "believe the risk of dehydration is lower than when outdoors" (10.9%).

・When asked about daily fluid intake, the most common response was "800 mL to less than 1 L" (27.7%), followed by "1 L to less than 1.5 L" (27.4%) and "500 mL to less than 800 mL" (22.0%). 54.8% of respondents are not meeting the recommended daily fluid intake for maintaining adult immunity.

・22.7% of respondents reported having experienced dehydration.

・When asked about preventive measures against dehydration, the top response was "drink fluids regularly" (89.9%), followed by "use air conditioning or fans" (64.1%) and "avoid direct sunlight with hats or umbrellas" (50.8%).

・In summer, long periods spent in cool, dry, air-conditioned rooms can lead to neglected hydration, increasing the risk of hidden dehydration. When asked if they had heard of the term "hidden dehydration," 37.9% responded "no."

Dr. Hideki Taniguchi Explains Signs and Prevention of Hidden Dehydration

・What is hidden dehydration?

Hidden dehydration refers to a state just before clinical dehydration occurs. In this condition, the body's water levels are lower than normal, but individuals are unaware of it.

While it often resolves naturally through eating and drinking, some cases may progress to full dehydration or become a precursor to heatstroke, especially in hot seasons.

In blood tests we conducted on the general public, about 20% of those aged 65 and older showed signs of hidden dehydration year-round. Even younger individuals may experience it upon waking or during hangovers.

・Signs of hidden dehydration

As the name suggests, symptoms are subtle and hard to detect. Focus on three organs most affected by dehydration to avoid missing the signs:

Brain: Reduced concentration, mental fogginess, dizziness upon standing

Gastrointestinal tract: Loss of appetite, irregular bowel movements (diarrhea or constipation)

Muscles: Weakness, muscle cramps, pain

Others: Fatigue, reduced saliva, dry skin, etc.

These symptoms are typically not severe enough to prompt a visit to the doctor, making them easy to overlook.

・Who, when, and where hidden dehydration is likely to occur

At-risk individuals: Irregular lifestyle, frequent overeating or excessive drinking, obesity, those on diets, adults aged 65 and older

At-risk times: Upon waking, before meals, after bathing

At-risk environments: Hot environments year-round, situations where drinking water is inconvenient, dry winter conditions, air-conditioned rooms, during or after alcohol consumption

Hidden dehydration can affect anyone regardless of age or gender. Preventing it from worsening is crucial.

・How to prevent hidden dehydration

Regular fluid intake and eating three balanced meals daily. Getting water from food is important—three meals can provide nearly 1 liter of water. For hydration, start by setting specific times to drink regularly. (Recommended: "6 ounces, 8 times a day"—about 180 mL per glass, eight times daily.) Pay special attention to hydration before bedtime, upon waking, and after bathing. Also, do not skip hydration after drinking alcohol, exercising, or using a sauna.

Having a water server at home makes it easy to drink water anytime, making it highly effective for preventing hidden dehydration.

Profile of Dr. Hideki Taniguchi

Director, Patient Support Center, Keiwa Hospital, Yokohama; Visiting Professor, Graduate School of Tokyo Medical and Health Sciences University; Anesthesiologist; Medical Doctor; Specialist in Anesthesiology

Specializes in water and electrolyte management, nutritional management, and oral rehydration therapy. Author of academic papers on dehydration and hidden dehydration, and of the book "The Science of Drinking for Life—The Manual for Hydration That Your Body Will Thank You For" (Hyōgensa).

Frequent commentator in newspapers, TV, and magazines. Runs "Taniguchi Seminar," a lifelong education site for medical professionals.

Feedback from Premium Water Subscribers

89.9% of subscribers reported drinking more water after signing up for a water server service.

Additionally, 88.5% listed "water" as their most commonly consumed beverage. Subscribers shared comments such as "Having the water server nearby makes it easy to drink water frequently," "the water tastes good," and "I never get tired of it."

About Premium Water "Fresh Natural Water"

Premium Water "Fresh Natural Water" is natural spring water that meets six strict criteria: "natural origin," "balanced minerals," "soft water," "pH level," "non-heated processing," and "freshness." While most natural bottled waters undergo heat treatment, Premium Water uses non-heated processing, preserving dissolved oxygen—a key indicator of water quality and taste—allowing consumers to enjoy the smooth, natural taste of pure spring water.

About Premium Water

Premium Water offers a home delivery (regular shipment) service, renting or selling water dispensers and delivering fresh water directly to customers’ homes.

It eliminates the need to carry heavy water bottles or boil water, providing delicious "Fresh Natural Water" anytime. Thanks to non-heated processing, the water retains its high quality and smooth taste. With a shelf life of approximately 6 months from production (unopened), "Fresh Natural Water" is also suitable for rolling stock—consuming while replenishing—as part of emergency preparedness.

Water dispensers are available in various styles: eco-friendly models that are budget- and environment-friendly, high-functionality bottom-loading models for easy bottle replacement even by those with limited strength, and elegant, design-focused models that blend seamlessly with home interiors.

For more information, visit the official website: https://premium-water.net/

Premium Water Official Website: https://premium-water.net

Premium Water Official X (formerly Twitter): https://x.com/premium_water

Premium Water Official Facebook: https://www.facebook.com/premiumwater.net

Premium Water Official Instagram: https://www.instagram.com/premium_water

Premium Water Official TikTok: https://www.tiktok.com/@premium_water_official