Introduction

Water stands as an indisputable necessity for all living organisms. Its presence on planet Earth’s surface, accounting for approximately 71%,¹ and the continuous exploration of water sources on other celestial bodies signify its integral significance. From determining evolutionary processes to shaping the Earth’s atmosphere, water holds the foundations for sustaining life.

The percentage of total water constituting the human body ranges from 70% in infants to 60% in adults.² Proper hydration and balance are pivotal for maintaining overall health. Advances in investigating the link between water and physical and mental health are expanding, offering a further comprehension of these relationships.

According to the European Food Safety Authority, the recommended water intake for adults is 2.0L per day for females and 2.5L per day for males, with adjustments for specific age groups.³ Factors such as physical exercise, fever, hot climates, or excessive fluid loss, necessitate an increase in water consumption, underscoring a complex network of hydration guidelines.

Nevertheless, the well-established properties of water include transporting nutrients, eliminating waste products, lubricating joints, protecting organs, and maintaining ideal body temperature.⁴ Therefore, adequate hydration daily is imperative for physiological body processes.

Additionally, recent studies are investigating the effects of hydration on brain function, exploring the association of water ingestion with mental health. These factors seem to be interlinked, with dehydration being associated with various mental disorders, including depression and anxiety.⁵

Hydration and physical health 

The human organism can only survive for a brief time without water. Hydration is therefore key to regulating normal bodily functions and organ health. Adequate hydration is therefore paramount to maintain a balanced water concentration in the body. This article presents some of the main benefits of water on the body.

Maintaining optimal organ and cellular function

The hydrodynamic properties of water play a significant role in maintaining cellular and tissue function by preserving normal fluid volume. Its ability to transport nutrients, electrolytes (such as sodium, potassium, and chloride), and oxygen within cells underlines its crucial role in facilitating proper biochemical and metabolic processes, while also maintaining cell shape and development.⁶ Furthermore, water supports mouth health by ensuring saliva production and conserving essential moisture in mucous membranes, aiding in normal respiratory system function.¹¹

Eliminates waste products

In addition to actively transporting nutrients and oxygen, proper water balance is instrumental in clearing out waste products from the body. Hydration helps dilute waste products such as metabolic waste, excess salts, and toxins, enabling excretion from the body through urine, sweating, and faeces. Water intake is principal in replenishing body fluids lost, particularly during regular physical activities. This hydrates the body and quenches thirst by restoring fluids lost from sweating.⁷

Provides joint lubrication and muscle health

Hydration maintains the optimal functionality of joints by lubricating them. Specifically, water constitutes the primary component of synovial fluid which are located within the cavities of synovial joints and are responsible for minimising friction between articular cartilage surfaces, allowing smoother and pain-free movement. Synovial fluid also acts as a shock absorber, preventing injuries and minimising the impact of exercise and weight-bearing activities.

Furthermore, hydration helps preserve the elasticity and lubricating properties of cartilage. Composed of 70% water, cartilage acts as a sponge, obtaining its properties through water-soluble nutrients. Overall, the flexibility and adequate hydration of joints contribute to preventing discomfort associated with various joint conditions, including osteoarthritis.⁸

Likewise, adequate hydration plays a crucial role in supporting muscle function. Upholding an electrolyte balance within muscle cells, facilitates demanding energy production through glucose and nutrient transport. Hydration may enhance endurance, and prevent fatigue and muscle cramps through temperature regulation during exercise. It also aids recovery and repair of muscle soreness post-exercise.⁹ 

Contributes to temperature balance

Water consumption is an optimal tool for thermoregulation, especially during exercise. Its capacity to sustain suitable body temperature not only reduces stress but also reinforces endurance, thereby enhancing overall exercise performance.

This stabilisation of body temperature is also essential for adapting to the fluctuating temperatures of the environment. Hydration is critical in both cold and hot climates due to water’s ability to absorb and distribute heat, as well as facilitate cooling down through water loss via sweating when necessary.¹⁰

Provides immune support

Adequate hydration supports the proper functioning of the immune system, which defends the body against pathogens. A hydrated body involves a homeostatic state of all tissues, with normal osmotic pressure, body temperature, and electrolyte balance. This equilibrium allows for competent elimination of toxins through the kidneys. Insufficient water consumption could result in kidney malfunction and restricted detoxification, potentially compromising the immune system’s ability to fight infections and leading to inflammation.

Thus, a well-hydrated body is vital for promoting the efficiency of the lymphatic system and thermoregulation, specifically during fevers. Respiratory and digestive tract moisture, by adequate water intake, significantly contributes to trapping and eliminating pathogens effectively, further supporting immune function.¹¹

Additional effects of adequate hydration

The advantages of maintaining balanced water levels within the body extend beyond the previously discussed aspects. Adequate hydration offers considerable benefits for numerous more physical activities, offering additional benefits.

Contributing to cardiovascular health

Ideal body water has a regulatory action in blood pressure, blood flow, and vessel health, offering a protective mechanism against cardiovascular diseases.¹²

Influencing skin health

Adequate water levels ensure normal skin hydration, physiology, and appearance. They maintain the skin’s natural protective barrier, preventing dermatologic issues like dryness, flakiness, and irritation.¹³

Impacting kidney health

Renal function benefits from adequate daily water intake, reducing the risk of kidney diseases, and kidney stones, and increasing the release of sodium and urea, optimising blood pressure.¹⁴

Affecting gastrointestinal health

Hydration promotes gut health, aids in relieving constipation, facilitates faeces elimination and influences the absorption of nutrients during digestion.¹⁵

Regulating weight management

Adequate water intake is positively associated with balanced body composition and weight management.¹⁵

Managing alcohol and dehydration-induced headaches

Water serves as a medium for detoxification, and staying hydrated while drinking alcohol helps prevent dehydration, even reducing headaches, including migraines.¹⁵

Hydration and mental health

Apart from establishing proper organ system functions through biochemical regulations, hydration is believed to be a key aspect of mental health. More precisely, water is considered vital for neural communication and brain function due to its ability to transport oxygen and nutrients to the brain while eliminating waste and toxins.

The preservation of a hydrating state affects the cognitive performance of an individual. Clear thinking, problem-solving, concentration, and memory are optimal when daily hydration needs are properly met. The association between appropriate brain activity and adequate water intake also extends to improved mood and sleeping habits.

Hormonal and neurotransmitter regulation supported by hydration influences stress, anxiety, and depression, contributing to overall mental well-being. Moreover, balanced fluid congestion is decisive for supporting brain structure and offering protection.^15,16

Dehydration and mental health disorders

While the connection between water consumption and mental health disorders is still under evaluation, dehydration can have adverse effects on mental health, exacerbating symptoms of anxiety and depression, and leading to cognitive impairment.

Scientific studies have validated that dehydration and hypohydration (the uncompensated loss of body water) are linked to increased tension and anxiety. Specific levels of body fluid loss can alter the activity of certain brain regions, influencing the autonomic nervous system. Precisely, lower water intake is connected to elevated levels of the stress hormone cortisol. Additionally, the renin-angiotensin-aldosterone system is affected by lower fluid intake, aiming to restore fluid balance, and contributing to changes in stress responses.¹⁷

Inadequate water consumption contribute to depression. The psychological effects of dehydration, including physical discomfort, sleep disturbances, and reduced cognitive performance may result in a negative mindset, potentially aggravating depressive feelings. Imbalances in neurotransmitters such as norepinephrine and serotonin, along with hormones like cortisol, should be considered when correlating lower water congestion to depression.⁵

Practical tips for hydrating

Adequate hydration has numerous evident effects on individual well-being. Developing healthy hydration habits and adhering to daily recommendations are fundamental steps for amending water balance. Understanding fluctuations in hydration needs based on demographics, age, pregnancy, and physical activity is pivotal to achieve optimal health.

Balancing water intake is essential, as excessive drinking can have negative consequences on overall health, potentially leading to hyponatraemia and osmolarity irregularities, conditions requiring medical care in severe cases. A simple self-assessment to check for overhydration is done by inspecting the colour of urine. Pale yellow or colourless urine may indicate an excess of water, though it should not be solely considered as an indication of overhydration.¹⁸

Water consumption is not confined to beverages alone. Dietary sources, especially fruits and vegetables may contain a high water content of up to 90%. Consequently, daily hydration recommendations may vary among populations. Individuals should assess their water balance and consider both fluid intake from beverages and solid foods, as well as water loss through urine, sweat, and faeces.¹⁹

Summary

In summary, water, an abundant and essential compound for living organisms on Earth, including humans, is undeniably associated with overall health and well-being. General recommendations for daily water congestion aim to provide instructions to individuals for a balanced water content and hydration level. Age, pregnancy, body temperature, fever, exercise, medications, alcohol, and caffeine are all factors affecting water volume and loss from the body, requiring modifications in daily hydration needs.

Adequate hydration has been extensively studied and is currently being evaluated for its impact on both physical and mental health. These studies cover the diverse aspects of hydration, ranging from organ and cellular function to waste elimination, joint lubrication, muscle health, temperature balance, immune support, cardiovascular health, skin, kidney, and gastrointestinal health. Additionally, weight management and alleviation of dehydration headaches are bonus l effects of hydration.

Moreover, poor hydration and mental health problems, including depression, anxiety and cognitive performance are correlated, highlighting the profound significance of hydration for mental well-being.