Hydration guide Part I

Summer is in full swing and the heat comes with it. As the thermometer creeps upwards, we need to be increasingly vigilant about staying optimally hydrated. What should we look out for? Not just drinking the right amount of water... This hydration guide will help you! Here come our hydra-tips!

Your level of hydration is a crucial factor for both health and sports performance. Water is an essential element of the human body, without it life is inconceivable. This sentence is so trivial and common knowledge for most of us. Right? Yet in everyday life, little attention is paid to optimal fluid intake when it comes to maintaining health or enhancing mental and/or sports performance. The water content of the human body varies with age: while for babies it makes up nearly 75% of their body weight, in the case of an elderly person it becomes only 55%.

What is water to us?

• a solvent and a transport medium for different nutrients,
• it is involved in the regulation of blood pressure, and
• the excretion of waste products, and
• the proper functioning of the joints and immune system, 
• it plays a role in regulating body temperature.

How much fluid do we need per day?

The World Health Organisation (WHO) recommends a daily intake of 3.7 litres for men and 2.7 litres for women.

Most of the body's fluid needs are met by the water and other drinks we have. To a lesser extent, the water content of foods and groceries such as soups, fresh vegetables and fruit contribute to an optimally hydrated state. The oxidation water formed in the body during the oxidation of nutrients in the various metabolic processes also supports adequate hydration, but the daily amount (about 300 ml/day) is not significant in relation to the recommendations.

How much fluid do we lose during the day?

It also depends on how active you are, how much you talk or even sing during the day. Fluid loss occurs through urine and stool excretion, breathing, vaporisation and via skin through sweating. The minimum daily urine excretion is about 500 ml. A further 700 ml of fluid is lost through the airways by breathing and speaking, and through the skin in case of an average adult. In addition to these water loss pathways, fluid is also lost with feces, approximately 100 ml per day. The amount of fluid lost through sweating is highly variable. The rate increases significantly with higher levels of physical activity and changes in environmental factors such as outside temperature and/or humidity. This is explained by the thermoregulatory mechanism. Water plays a central role in maintaining the temperature of the human body, which fluctuates from day to day but is generally constant at between 35.8°C and 37.5°C, through the circulation of blood. For example, if the blood supply to a particular area (brain, muscle, certain organs) is reduced, the blood flow will be less able to transport heat, so the core temperature will rise.

When do we get thirsty?

The onset of thirst depends on the constriction of body fluid and its decrease in volume. After a rise in blood plasma osmolality of about 2% (above 290 mOsm/kg), the urge to drink fluids, thirst, appears.

What is dehydration?

Dehydration is when there is a fluid and/or electrolyte deficiency in the body. Dehydration can be associated with the loss of various electrolytes such as sodium, potassium, magnesium, chlorine. Depending on the proportion of water and minerals lost, we can distinguish isotonic, hypertonic or hypotonic dehydration. All types of dehydration cause problems. Interestingly, an over-hydrated state can also be described as dehydration. In this case, too much water consumption causes, for example, headaches resulting in cell swelling and low electrolyte concentrations. This phenomenon is usually associated with increased water consumption, the most risky complication being brain oedema, which is a life-threatening condition. So, unless you have lost a significant amount of fluid, you should definitely not drink 5-6 litres of water a day.

Dehydration has a number of negative consequences, including:

• increasing the incidence of constipation and kidney stones,
• increases the risk of infectious diseases due to dry mucous membranes,
• leads to a decrease in concentration and other cognitive functions.
• it is of a particular relevance to athletes is the consensus in the professional literature that a loss of 2-3% of body weight clearly leads to a reduction in physical and mental performance. 

How do you know that you are dehydrated?

A series of small and unpleasant symptoms tell us if we need more fluids. If you experience any of the following, remember to hydrate more often:

• dry mouth and mucous membranes
• headaches, dizziness
• loss of appetite
• increased thirst
• infrequent urination
• medium to dark yellow, concentrated urine
• fatigue, lethargy
• reduced reaction time
• rapid pulse

In the next section, you will learn about drinks and foods that can keep you hydrated.

Sources:

Rodriguez, N.R. (2009): American College of Sports Medicine position stand. Nutrition and athletic performance. Med Sci Sports Exerc.

Fonyó (2011): Az orvosi élettan tankönyve

Tihanyi (2012): Teljesítményfokozó Sporttáplálkozás