Importance of Water for Health
The subject of water and health is vital. Humans can live for 5 minutes without breathing, 6 days without drinking water, and 40 days without eating. Water is the most critical food for life.
Although the proportion varies slightly with age and sex, approximately 65% of a person’s body is water. An adult weighing 70 kg therefore contains about 45 kg of water.
• When water loss reaches 1–1.5%, thirst, impaired coordination, loss of appetite, increased rectal temperature, irritability, fatigue and an increased heart rate occur.
• When water loss reaches 6-7%, headache, difficulty breathing, difficulty speaking and difficulty remembering occur.
• If a person loses 8% of their body water—approximately 3.6 kg in this example—bodily functions begin to be disrupted, with consequences that can extend to death.
Functions of Water in the Body
1. Water is used as a building material in the body. Approximately 75% of muscles, 25% of bone tissue, 20% of fat tissue and 10% of dental tissue are made up of water. Therefore, water consumption significantly affects body structure.
2. Water acts as a carrier in the body. At the cellular level, it transports nutrients, hormones and enzymes needed by cells, as well as waste products of cellular activity.
Water also acts as a solvent and carrier in bodily secretions such as saliva. It plays a transport role in the digestive and excretory systems as well; digestion and excretion cannot take place without water.
3. Water plays a vital role in regulating body temperature. Excess heat is removed through sweating when the body rises above normal temperature. The reason we sweat when we exert intense effort is that the body tries to remove excess heat with water.
We want to drink cold water in hot weather because the body seeks to balance the heat with the cold water it takes. Likewise, the desire to drink hot drinks in cold weather is due to the body wanting to maintain its heat balance with the heat contained in the drink.
4. Water protects the body against pressure and impact. Water prevents the adverse effects of abrasion and friction by lubrication in joints, mobile organs such as the eyes and eyelids, and internal organs. In addition, it protects against possible external impacts by surrounding organism structures, as in the case of the brain and the fetus.
How Much Water Should You Drink Per Day?
Short Answer: Healthy individuals should drink between 1-3 liters of water daily, depending on age, gender, body structure and daily activity intensity. Generally, this value is 1.5-2 liters for young and adult women and 2-2.5 liters for men. However, an individual must know approximately how much water they should drink according to their characteristics. For example, for an individual who needs to drink approximately 2.5 liters of water daily, drinking 1.5 liters daily would not be the correct behavior regarding healthy nutrition. The amount of water an individual should consume daily, depending on age, gender, body structure, and daily activity intensity, is explained in detail below.
The body meets its daily water needs from 3 sources. In general, the daily water requirement;
1. 50% from drinking water and water-based beverages,
2. 35% from food (For detailed information about the amount of water found in food, see Water in Foods; Forms, Characteristics and Importance)
3. 15% is provided by water produced from metabolic activities. As a result of metabolic activities, the body produces approximately 300 mL of water per day.
The amount of water needed per day is usually calculated based on the energy spent by the individual in their daily activities. A healthy adult spends approximately 1000-2500 calories of energy per day in basal metabolic activities. At this point, the body requires approximately 1 mL of water for each calorie spent. Therefore, the amount of water a healthy adult needs on a day at rest is 1.5-2.5 liters. (For detailed information about basal metabolism and the amount of energy the body spends in activities, see Energy Metabolism – II; Energy Expended in the Body)
The activities performed by individuals in daily life will increase the energy they spend and the amount of water they need. The table below shows the energy spent in some activities and the water loss that occurs as a result of these activities;
The amount of energy spent daily by an individual working at a desk job and the amount of water needed daily depending on gender, age and body structure are as follows;
(The table presents average values on specific scales. By adjusting these values proportionally for age and body weight, a person can estimate their own water needs.)
Using the information above, let’s consider an example of how much water a person needs to consume:
• According to the table, a healthy 35-year-old man who weighs 80 kg and has a desk job needs approximately 2.2 liters of water for his working day.
• If this individual performs 1 hour of walking, 1 hour of cooking and 2 hours of watching television in addition to his daily work, his body will lose approximately 2 liters of water due to these activities.
• Therefore, the individual’s daily water need will be 4.2 liters. Since the body will meet 50% of this need from water and water-based beverages, 35% from food and 15% from water produced in metabolism, this individual needs to drink at least 2.1 liters of water for that day.
It is helpful to pay attention to the following points regarding water consumption;
1. In water consumption, care should be taken to preserve the amount of water the body has and to consume enough water to balance the amount of water excreted from the body. When thirst is felt, care should be taken to quench the thirst sufficiently. When the density of blood plasma increases by 1%, the thirst-related center in the brain is stimulated and the feeling of thirst occurs.
The point to pay attention to regarding water balance is urine color. Light yellow is the standard color of urine, and a darkening or increasing darkness of this color indicates that the body is not getting enough water.
2. As it is known, water-based beverages such as tea and coffee are very popular and consumed a lot. However, consuming these beverages to meet water needs is not appropriate. These beverages have a high diuretic effect. Drinks with high diuretic effects can relieve the feeling of thirst, but they cause more water to be excreted from the body than the amount consumed. Therefore, a healthy individual should drink as much water as they drink tea and coffee so that the body’s water balance is not disrupted.
3. The individual’s habit of frequently eating foods with low water content, such as fast food, causes them not to get enough water from food. Therefore, individuals who eat foods with low water content need to drink more water and water-based beverages.
4. Drinking water must also be potable and meet the quality standards established for it. These standards and criteria vary by country and institution. For more detail, see Quality Characteristics That Drinking Water Should Have.
All these data and evaluations are given, considering the individual is healthy. It should be known that the need for water will increase even more in cases of vomiting, diarrhea, and similar illnesses, as well as in cases of pregnancy or heavy working conditions.
Note: This article is intended solely for general informational purposes. It does not constitute medical advice or personalized nutritional guidance. Nutritional needs may vary from person to person. Always consult a healthcare professional or a registered dietitian before making any dietary changes.
References
Raymond, J. L., & Morrow, K. (2023). Krause ve Mahan Besin ve Beslenme Bakım Süreci (16. baskı; G. Akbulut, Çev. Ed.). Nobel Tıp Kitabevleri.
Aksoy, M. (Ed.). (2022). Beslenme Biyokimyası (7. baskı). Ankara Nobel Tıp Kitabevleri.
Sencer, E., & Orhan, Y. (2005). Beslenme. İstanbul Medikal Yayıncılık.
Gökalp, H. Y., Nas, S., & Certel, M. (2002). Biyokimya-I: Temel Yapılar ve Kavramlar. Pamukkale Üniversitesi Mühendislik Fakültesi.
EFSA Panel on Dietetic Products, Nutrition, and Allergies (NDA). (2010). Scientific Opinion on Dietary Reference Values for water. EFSA Journal, 8(3), 1459.
Institute of Medicine. (2005). Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate. The National Academies Press.
World Health Organization. (2026). Guidelines for drinking-water quality (4th ed., incorporating the first, second and third addenda).
Here’s an article that might interest you: Quality Characteristics That Drinking Water Should Have
Halil İbrahim Akgül
Halil Ibrahim Akgul, Ph.D., is an Assistant Professor of Food Engineering at Bayburt University, where he works in the Division of Food Sciences within the Faculty of Engineering. He received his B.Sc. in Food Engineering from Akdeniz University in 2010, followed by an M.Sc. and a Ph.D. in Food Engineering from Atatürk University in 2015 and 2020, respectively. His formally recognised academic fields are Food Sciences and Engineering, Food Technologies, Dairy and Dairy Products Technology, and Food Microbiology.
Dr. Akgul has more than fifteen years of professional, research, and academic experience in food science. Between 2011 and 2013, he worked as the food engineer responsible for operations at the Pilot Dairy and Bread Factory of Atatürk University’s Directorate of Agricultural Enterprises. This industrial experience, combined with his subsequent academic research, gave him extensive practical and scientific knowledge of milk processing, dairy production, food quality, hygiene, and product development.
His research is primarily focused on milk and dairy products, dairy microbiology, starter cultures, lactic acid bacteria, exopolysaccharides, butter technology, and the physicochemical, microbiological, sensory, and nutritional properties of foods. His studies have examined the quality and fatty-acid composition of traditional butter, aroma formation in butter produced with different starter cultures, raw-milk quality, the characterisation and antioxidant activity of bacterial exopolysaccharides, traditional dairy products such as çökelek and karın kaymağı, colostrum powder, and the use of fruit-derived ingredients in ice cream production.
His academic record includes peer-reviewed research articles published in national and international journals, including Mljekarstvo, Acta Scientiarum Technology, the Journal of Food Safety and Food Quality, the International Journal of Food Engineering, the Atatürk University Journal of Agricultural Faculty, and ATA Food Journal. Four of the research articles currently listed in his university profile were published in SCI-Expanded-indexed journals. He has also contributed to twelve national and international conference papers and presentations covering dairy products, food microbiology, butter quality, fatty-acid composition, starter cultures, exopolysaccharide-producing bacteria, colostrum, traditional foods, and functional ice-cream formulations.
Dr. Akgul has participated as a researcher or adviser in eleven completed scientific and applied research projects. These projects have addressed the modernisation of pilot dairy-processing facilities; the production and quality characteristics of colostrum powder; the physicochemical and microbiological quality of butter and raw milk; the identification of exopolysaccharide-producing lactic acid bacteria; the development and production optimisation of starter cultures for mould-ripened cheese; the standardisation of traditional dairy products; and the use of sloe berry and persimmon fibre in ice-cream production.
His teaching experience spans undergraduate, associate-degree, and graduate education. The courses he has taught include Food Chemistry, Analytical Chemistry, General Chemistry, Organic Chemistry, Fermented Dairy Products Technology, Butter Production and Processing Technology, Healthy Living and Nutrition, Organic Agriculture and Food, Popular Science, Digital Literacy, and Information Technologies. Through these courses, he combines fundamental food chemistry and engineering principles with dairy technology, nutrition, scientific literacy, and the practical communication of scientific knowledge.
He is the founder and Editor-in-Chief of Gıda ve Sağlık, a multilingual digital publication devoted to food, nutrition, health, food chemistry, food microbiology, and culinary science. Through this platform, he draws upon his academic background, teaching experience, research activity, and practical knowledge of food production to present scientifically grounded information in a detailed and accessible form for an international readership.