How to Eat Healthy – Hydration
Water is crucial for life. It is an essential nutrient and the only one for which an absence will prove lethal within days1. Water homeostasis and proper hydration are key to human health and survival.
Water has many roles in the human body and as a multifunctional constituent it acts as2,3:
- building material
- a solvent, a reaction medium, a reactant, and a reaction product
- transporter for nutrients and waste products
- thermoregulation, regulating body temperature
- lubricant, lubricating joints and internal organs
- shock absorber
- provides structure to cells and tissues
- supports bodily system functions
Why is water so crucial for the human body and life?
Water is vital for life because it has many critical functions. It is the largest constituent of the human body, comprising approximately 45% to 75% of a person’s body weight (ranging from about 75% of body weight in infants to 55% in the elderly)3. A simple way to understand the importance of water is to analyze the fluid composition of the human body4,5:
- The human adult body is up to 60% water
- Brain and heart are composed of around 73% water
- Lungs about 83% water
- The skin contains 64% water
- Muscles and kidneys are 79%
- Fat tissue 10 to 40%
- Bones about 31% (even bones are “watery”)
- The blood plasma is around 90% water
Water is essential to maintain cellular homeostasis and vascular volume3. It is also a transport medium in the body that delivers nutrients and removes toxic wastes. There is a constant control within the body, between water intake and water loss, along with electrolytes to reach water balance and homeostasis. This control and water balance regulation is impressively precise. A 1% of body water loss is usually compensated within 24 hours.
Dehydration develops from inadequate fluid intake or excessive fluid losses, and overhydration can result from excessive water (or fluid) intake with or without proper electrolyte replacement6. Evidence shows that there is a correlation between fluid imbalance (both dehydration and overhydration) and disease, morbidity and mortality2,7.
In the view of this important but delicate balance, how much should we drink?
Each day humans, as other animals, must consume a certain amount of water to survive. The necessary fluid intake for healthy adults can vary markedly depending on different factors such as age and gender, activity level, geographical location, environmental exposure, diet, and social activities. However, water intake should be sufficient to balance losses, ensuring adequate hydration of all body tissues, which is of paramount importance for a healthy life. Therefore, water requirements are not defined based on minimal intake because considering the numerous individual factors and variables mentioned above, that could easily lead to water deficit. Instead, adequate water intake recommendations are based on experimentally derived intake levels that are expected to meet the nutritional adequacy of a healthy population, accounting for average water inputs and outputs2.
Average daily water inputs and outputs for fluid balance in adults are shown in the Figure below from the article “The Hydration Equation: Update on Water Balance and Cognitive Performance.” 6:
Average daily fluid balance in adults. 1 cup = 237 mL. (Based upon estimates reported by Jequier E, Constant F. Water as an essential nutrient: the physiological basis of hydration. European Journal of Clinical Nutrition 2010;64(2):115–23.)
6 – Source: Riebl SK, Davy BM. The Hydration Equation: Update on Water Balance and Cognitive Performance. ACSM’s Health & Fitness Journal17(6):21-28, November/December 2013.
Dietary Reference Values for Water
The Food and Nutrition Board of the Institute of Medicine (IOM) from the National Academy of Sciences published the US Dietary Reference Intake for water both in 2005 and 20063,8.
The scientific committee established an adequate intake (AI) for total water to prevent the harmful effects of dehydration. Every day, close to a liter of water is lost from breathing, perspiring and bowel movements, and the average urine output for adults is up to 1.5 liters a day. Consequently, the IOM AI (for total water) for sedentary adults (19–50 years) is:
- Man: 3.7 liters per day
- Women 2.7 liters per day
About 81% of this water intake is represented by drinking fluids (water and other beverages) with 19% of water being provided by foods. Based on this, the actual AI recommendation for fluid intake is:
- Man: 3.0 liters per day
- Women: 2.2 liters per day
The European Food Safety Authority (EFSA) published in 2010 the Dietary Reference Values for water. The reference values for total water intake include water from drinking water, beverages of all kinds, and from food moisture. EFSA defines adequate intake as 2.0 L/day for females and 2.5 L/day for males, considering that these values are only applicable to conditions of moderate environmental temperature and moderate physical activity levels9.
Why do we need water?
As we have explained, water is one of the main constituents of our body, organs, tissues and cells, and it’s vital for life2. Water is essential for practically all bodily functions, and is particularly important for thermoregulation, and for the proper working and synergy within the human systems, such as digestive, excretory, respiratory and cardiovascular9. Water is also essential for cellular renewal and regeneration and enough consumption of this essential nutrient has been scientifically proven to have many health benefits.
Benefits of Adequate Water Intake
- Inadequate water intake, whether dehydration or overhydration, has been associated with morbidity and mortality7.
- Dehydration has been linked with urological, gastrointestinal, circulatory, and neurological disorders7.
- Overhydration is related to hyponatremia, cardiopulmonary disorders, edema, gastrointestinal dysfunction, and postoperative complications7.
- Decrease the risk of certain cancers10,11,12.
- Improve energy levels13.
- Enhance mood and brain performance: mainly cognitive functions such as attention, memory, or executive functions and motor coordination14,15,16,17,18,19.
- Dehydration may lead to mood and cognition impairment including decreased alertness and increased sleepiness and confusion, fatigue and tiredness, increased perception of task difficulty, lower concentration, and increased tension/anxiety. There is also an increase in negative emotions such as anger, hostility and depression16,20,21,22.
- Changes in sleep/wake parameters20.
- May help relieve constipation23,24.
- May prevent and help improve headaches and reduce migraine headache frequency and severity13,25,26,27.
- Lower risk of kidney stones formation16,27,28.
- Weight management and improve body composition16,29,30.
- Improve physical and athletic performance31,32.
- Dehydration may increase oxidative stress and DNA damage during exercise, and induce a greater cellular and whole-body stress33,34.
Researchers have shown that decreased water consumption is associated with bladder and lower urinary tract cancer. The hypothesis behind this theory is that decreased fluid intake could result in a greater concentration of carcinogens in the urine or in a prolonged time of contact with the bladder mucosa because of less frequent micturition10,11,12. However, when evaluating fluid intake and health, especially cancer risk, caution must be taken with carcinogenic or anticarcinogenic components present in different beverages that are going to be excreted in the urine and may play an important role in the process10.
Furthermore, increased fluid consumption was suggested to have a favorable effect on colorectal cancer risk. Again, researcher’s theory, which is aligned with human biology, is that low fluid intake (in conjunction with the fact that we excrete about 80-200 ml of water a day in waste) may increase the risk of colorectal cancer. Similar to the bladder hypothesis, the increased bowel transit time will increase the contact time of carcinogens with mucous membranes in the colon and rectum, which will drive up cancer risk10.
How do I know if I am drinking enough?
Hydration refers to having adequate fluid within body tissues, and it can be determined through a variety of methods. Hydration status can be tested in a laboratory but there are also some ways to measure it without having to resort to a laboratory setting, with measures such as thirst, 24-hour urine volume, change in weight (i.e., body mass) and urine color6.
At first it may be hard to assess your level of thirst and keep record of the amount of water you are drinking daily. Following general recommendations is the easiest way to keep track of your water intake. However, ideally and with time, having the ability to get in touch with your body, feeling thirsty and drinking accordingly would be the best way to autoregulate your hydration and find your true individual water balance.
How do I know if I am not drinking enough?
Mild dehydration, corresponding to only 1–2% of body weight loss in adults, can lead to a significant impairment in both cognitive and physical performance.
Some of the dehydration symptoms include2,13:
- Tiredness/ fatigue
- Poor concentration
- Extreme thirst
- Dark-colored urine
- Confusion or delirium (especially in the elderly)
Although dehydration may affect anyone, the condition is especially dangerous for young children and elderly adults. Studies suggest that dehydration has greater detrimental effects in these vulnerable populations and close attention should be given to their hydration levels2,17,35.
Dehydration may affect1:
- Physical performance
- Cognitive performance
- Gastrointestinal function
- Kidney function
- Heart function and hemodynamic response
The problem is not just dehydration but also the intake of sweetened beverages, such as soft drinks and teas, that have been shown to impair cognitive function in adolescents. To improve cognitive performance, especially in more vulnerable and commercially influenceable populations, such as children and adolescents, public health interventions should focus on increasing hydration status and decreasing consumption of sugar-sweetened beverages36.
Hyperhydration, although not common, is also possible, especially during extreme and extended-duration exercise or in the case of hyponatremia (low sodium concentration). Symptoms of water intoxication may be fatigue, lethargy, disorientation, confusion, headache, nausea, vomiting, and, if not treated properly, coma and death. Overhydration signs and symptoms (i.e., light-headedness, dizziness, headaches, nausea, fatigue) can be very similar to those of dehydration1.
What should I drink?
Water is the fluid nature gives to all living things. Herbal teas, infused water and organic coffee (depending on individual situation and characteristics) can also be good sources of hydration. Green juice can be introduced into a healthy living nutrition along with fresh nutritious fruits and vegetables, which may provide about 20% of total water intake daily.
Not just the quantity but the quality of water you ingest are of paramount importance. Your bodily functions would be compromised without enough water, affecting all your cells, tissues and organs. Similarly, if that water is devoid of energy and nutrients, or loaded with artificial additives and harmful toxicants, the negative impacts will be felt throughout your system.
We believe that alkaline water, that has been running across the planet earth, through natural rocks and land formations, rich in pure minerals, is the best water, not just to drink but to bathe in. Sadly, most of us don’t have access to this water. Both tap and bottled water have been found to contain harmful substances, things like microplastics, chloride, fluoride and endocrine disruptors. That is the reason we recommend our patients to use distilled or purified water and glass bottles/ jars. Distilled or purified waters are devoid of natural occurring minerals, but that is the only way to guarantee that the water you are drinking is not carrying harmful substances. You can always add back some minerals to it, adding some well sourced salt or trace minerals, and supporting your body with a highly nutrient-dense diet that supplies the necessary minerals through raw living plants.
The first step towards health and healing is to stop harming the body, to stop exposing it to toxicants, therefore, drink mostly water and source it well.
Furthermore, what every single person should avoid is sugar-sweetened beverages (e.g., soda, sweetened tea and juices). Studies show that drinking water as a replacement for sugar-sweetened beverages, juice, or whole milk has clear effects on energy intake, reducing it by about 10–13% of total energy intake 1. This may be an important tool to fight the current pandemics of obesity, metabolic disease and associated disorders. Also important is the role sugar plays in nearly every single chronic and lifestyle disease, namely cancer. If you want to be healthy and prevent cancer, cut out sugar completely! And drink plain water.
Proper hydration is the keystone for any nourishing program and for the renewal and regeneration of your cells and body. If you want to be healthy, vibrant and feel great, drink enough pure WATER!
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- Jéquier E, Constant F. Water as an essential nutrient: the physiological basis of hydration. Eur J Clin Nutr. 2010 Feb;64(2):115-23. doi: 10.1038/ejcn.2009.111. Epub 2009 Sep 2. PMID: 19724292.
- Dietary Reference Intakes (2006). The Essential Guide to Nutrients Requirements. Institute of Medicine of the National Academies: Washington DC, 543 pp.
- Forbes RM, Cooper AR, Mitchell HH. The composition of the adult human body as determined by chemical analysis. J Biol Chem. 1953 Jul;203(1):359-66. PMID: 13069519.
- Mitchell, H. H., T. S. Hamilton, F. R. Steggerda and H. W. Bean. The chemical composition of the adult human body and its bearing on the biochemistry of growth. J Biol Chem. 1945; 158: 625-637. DOI:10.1016/s0021-9258(19)51339-4
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- Institute of Medicine 2005. Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate. Washington, DC: The National Academies Press. https://doi.org/10.17226/10925.
- EFSA Panel on Dietetic Products, Nutrition, and Allergies (NDA); Scientific Opinion on Dietary reference values for water. EFSA Journal 2010; 8( 3):1459. [48 pp.]. doi:10.2903/j.efsa.2010.1459.
- Altieri A, La Vecchia C, Negri E. Fluid intake and risk of bladder and other cancers. Eur J Clin Nutr. 2003 Dec;57 Suppl 2:S59-68. doi: 10.1038/sj.ejcn.1601903. PMID: 14681715.
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- Braver DJ, Modan M, Chêtrit A, Lusky A, Braf Z. Drinking, micturition habits, and urine concentration as potential risk factors in urinary bladder cancer. J Natl Cancer Inst. 1987 Mar;78(3):437-40. PMID: 3469457.
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Vanessa Pinto graduated with a degree in Biology and Masters in Ecology from Lisbon University. After graduating, she underwent a series of professional and personal growth experiences, including being an officer in the Portuguese Army, working in countries as diverse as Iceland and Costa Rica. Vanessa became certified as a Yoga and Meditation teacher in rural India.
Being a compassionate person by nature, Vanessa is able to bring her connectedness when working with others while enhancing the importance and practicality of a pragmatic evidence-based approach to facilitating lasting and permanent change. Vanessa is a certified health coach whose specialties are nutrition, exercise, and mind/ body connection. She works both in Portugal, Thailand and USA, where she develops her work closely with people diagnosed with cancer, mainly in the areas of nutrition, movement and health education.