Water, together with food and air, is the most precious asset for man: his body, in fact, is made up of a large part of water, which is taken during the day through the introduction of liquids with drinks and foods.
Water is really important for the proper functioning of the body, so much so that it is important to take at least 1.5 / 2 liters per day, which can go up to double or more in exceptional cases, such as:
- too intense sweating, typical in summer and with high humidity;
- a high loss of fluids due to various conditions and pathologies (for example prolonged diarrhea / vomiting; severe burns …)
- during intense and prolonged physical activities;
- in individuals with high% of lean mass and basal metabolic rate (for example in body builders).
But how long can a man resist without drinking?
An exact answer does not exist, because it depends on a large amount of factors, mainly:
- gender of the subject;
- basal metabolic rate;
- age of the subject;
- the build of the subject;
- general state of health.
I give you some examples. With the same temperature, humidity and general health conditions:
- a newborn baby would last for a third of the time of an adult man;
- an 80-year-old would resist much less than a subject by mid-years;
- a body builder would resist less than an individual with “normal” muscle mass, since his basal metabolic rate (and therefore his daily water requirement, values that are directly proportionate) is higher than normal;
- a woman has the potential to resist longer than a male, because she has an average lower basal metabolic rate and tends to have more liquid resources due to higher water retention;
- a pregnant woman endures less without drinking than a non-pregnant woman;
- a very anxious person has a prolonged resistance to dehydration, less than a calm person;
- a professional endurance sports athlete (therefore who does not have high muscle mass, as happens in power sports athletes) has a greater resistance to dehydration than a sedentary individual and a power sports athlete;
- a smoker has less resistance to dehydration than a non-smoker;
- a healthy subject resists more without hydration, rather than one who suffers from vomiting, diarrhea, diabetes, heart disease and severe burns: general health is very important to ensure the highest possible resistance.
Resistance also depends on various external factors, such as the type of environment (and therefore temperature and humidity ) in which you are located: for the same subject, in the desert you would need four liters of water per day for proper hydration, while at mild temperatures less than half would be enough. The daily water requirement also depends heavily on the type of activity you carry out: when you sleep , for example, you reduce the loss of fluids, while when you carry out strenuous work – perhaps carried out under the summer sun – it can obviously cause you to lose a great deal quantity of water and minerals.
Generally speaking, with an ambient temperature of around 15 ° C and without excessive efforts, a healthy 40-year-old adult human being can withstand an entire week on average without drinking , as long as it feeds at least on the liquids contained in fresh food (especially fruit and vegetables). However, dehydration has consequences in a short time, often even serious: without water the volume (i.e. our circulating blood volume) gradually decreases and when we go from a normal level of about 5 liters, from a level below 3, 5 liters, we witness the appearance of the following symptoms:
- asthenia (weakness);
- general malaise;
- increased respiratory rate;
- arterial hypotension;
- visual / auditory hallucinations;